Very Long Baseline Interferometry (VLBI) is a truly global scientific effort that demands rigorous coordination among a network of telescopes distributed worldwide. Central to this collaboration is the generation and distribution of a synchronized observation plan, a task typically called scheduling. Given a network of telescopes, a catalog of celestial sources, and a constrained time window, the goal of scheduling is to find an optimal sequence of observations to achieve the best possible scientific outcomes.

The complexity of this task arises from the virtually infinite number of potential schedules, making it practically impossible to find the most perfect solution. Instead, the objective is to generate a schedule that balances quality with practical constraints. Additionally, numerous optimization criteria must be considered, such as maximizing the number of observations for increased redundancy, ensuring a well-distributed coverage in azimuth and elevation angles to mitigate atmospheric effects, and achieving a balanced distribution of observations across the network and sources to enhance the parameter estimation process. Unfortunately, many of these criteria are in direct conflict with each other, further complicating the optimization process.

However, the importance of optimized scheduling cannot be overstated, as it directly determines the data available for analysis and, consequently, the quality of the scientific results. In recent years, significant progress has been made in VLBI scheduling algorithms. State-of-the-art practices involve generating hundreds of potential schedules for each experiment and using simulations to evaluate and select the optimal one. Nowadays, developing advanced scheduling algorithms requires a multifaceted approach, encompassing the creation of logical observation sequences, the generation of high-quality simulations, and the application of cutting-edge analysis and parameter estimation techniques. Additionally, new observing scenarios emerging from upcoming satellite missions, e.g. Genesis, combined with the more interdisciplinary application of VLBI resources, are fundamentally changing scheduling optimization objectives.

In this lecture, I will give a brief introduction to VLBI scheduling, highlighting its unique and exciting challenges. I will discuss recent advancements in scheduling algorithms and their impact on VLBI science. Furthermore, I will provide insights into future challenges and opportunities.

How to cite: Schartner, M.: The art of VLBI scheduling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6899, https://doi.org/10.5194/egusphere-egu25-6899, 2025.

Gravity measurements and geoid determination is a fundamental pillar of geodesy, and despite of roots going back more than two centuries, it is still a very active research field, with satellite and airborne data collection finally making global detailed gravity field coverage and thus a few-cm accuracy geoid within reach, a holy grail of geodesy for decades. Recent years have seen major efforts to cover the most inaccessible areas of the planet with gravity, especially the polar and mountainous areas, thanks to the development of airborne gravity sensors and long-range data campaigns. Parallel with this, climate applications of gravity measurements, both in space and in situ, have made gravity field change measurements more relevant than ever, especially for understanding global sea level rise and the melting of the large icesheets. Ongoing R&D in developing quantum methods for both in-situ, kinematic and space applications further points to new directions and applications for geodetic, geophysical and environmental applications of gravity field data, securing gravity field science key developments in the years to come. The Vening-Meinesz talk will address many recent developments in the above fields, and highlights the new opportunities for the next generation of geodesists.   

How to cite: Forsberg, R.: Gravity, Climate and Quantum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14370, https://doi.org/10.5194/egusphere-egu25-14370, 2025.

The tectonic framework of Bhutan Himalaya documents significant along-strike variability in crustal structure and deformation. To visualize this spatial and depth variability, we compile an extensive dataset of surface-wave phase velocities derived from seismic ambient noise and teleseismic earthquakes recorded by the temporary GANSSER network (2013-2014) in Bhutan, aiming to produce Rayleigh phase-velocity maps over the period range of 4 to 50 seconds. We translate the phase-velocity maps into a 3-D shear-wave velocity model stretching from the surface to a depth of 42 kilometres. The employed methodologies enable imaging of the upper to mid-crustal and lower crustal velocity anomalies with a lateral resolution of approximately 25 km. The obtained tomographic model fills a void in the prior established shear-wave velocity structure of Bhutan, encompassing depths from upper-crustal to lowermost crust. Our findings indicate notable mid-crustal to lower-crustal high phase velocity anomalies in central Bhutan (around 90.5). The presence of this significant anomaly within the mid- to lower crustal layer may indicate localized stress accumulation along the Main Himalayan Thrust (MHT) resulting from the interaction of the dipping and sub-horizontal Moho. This area might act as a stress concentration zone, resulting in increased deformation and enhanced shear-wave velocity in the crust. Minor fluctuations in velocity across latitude may result from variations in the local geometry of MHT (dip or ramp-flat transition). Localised high shear velocity in western Bhutan may indicate a zone of crustal thickening. Northeastern Bhutan exhibits modest shear velocity, possibly because of a flat Moho and the partial creeping behaviour of the MHT.

How to cite: Kumar, G. and Tiwari, A. K.: Multiscale Surface Wave Tomography of the Bhutan Himalayas using Ambient Seismic Noise and Teleseismic Earthquake Data , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1021, https://doi.org/10.5194/egusphere-egu25-1021, 2025.

Southeastern Tibet, a segment of the eastern Himalayan Syntaxis, is a significantly deformed area resulting from multistage subduction and the ongoing collision of the Indian and Asian tectonic plates. The region has a clockwise material movement around the indenting corner of the Indian plate, evident on the surface as strike-slip faults aligned with the Himalayan Arc. Numerous scientific studies have focused on the east-west extension and tectonic history of southeastern Tibet; however, the scientific enquiries regarding the depth constraints of the crustal flow process—specifically, whether it is confined to the middle crust or extends to the lower crust beneath southeastern Tibet—remain unresolved. This study employs ambient noise tomography to  examine a 3-D high-resolution crustal velocity model for the region, which is crucial for unravelling the mechanisms that regulate crustal deformation and evolution in active orogenic systems. To do this, we examined ambient noise data from 48 seismic stations of the XE network, operational from 2003 to 2004. We obtained Rayleigh wave phase velocities ranging from 4 to 60 seconds and subsequently inverted them to develop a 3-D shear wave velocity model of the region extending to depths of 50 km. Our results reveal persistent low shear wave velocity zones at depths of 15–25 km (within the mid-crust), notably observed between the Indus Tsangpo suture and the Bangong-Nujiang Suture. We contend that the detected low-velocity zones are only linked to mid-crustal channel flow, a mechanism presumably essential for comprehending crustal deformation. Our findings provide significant constraints on the depth localisation of crustal channel flow and the interaction of tectonic forces in southern Tibet, enhancing the overall comprehension of Eastern Syntaxial tectonics.

How to cite: Mandi, A., Kumar, G., Bishoyi, N., and Tiwari, A. K.: 3-D Crustal Shear Wave Velocity Tomography Using Seismic Ambient Noise Data in Southeast Tibet, Close to Namcha Barwa Mountain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1178, https://doi.org/10.5194/egusphere-egu25-1178, 2025.

With the continuous development of deep learning technologies, fault prediction techniques based on various neural networks have been evolving. The deep learning modules based on U-Net residual networks have shown significant advantages in both learning efficiency and effectiveness. In this paper, we propose a deep learning model that integrates a 3D U-Net residual architecture, Convolutional Block Attention Module (CBAM), and Multi-scale Enhanced Global Attention (MEGA) module for automatic seismic fault detection and segmentation. This model can effectively handle complex 3D seismic data, fully exploiting both spatial and channel information, significantly improving the prediction accuracy for small faults, while only slightly increasing the computational cost.

Firstly, the model uses the 3D U-Net as the backbone framework, where the residual blocks (BasicRes) extract features through multiple convolution layers. The CBAM module is incorporated to apply attention weighting, enhancing the model's ability to focus on critical information. The CBAM module combines channel attention and spatial attention, effectively adjusting the importance of feature maps from different dimensions, enabling the model to identify potential fault features in complex seismic data.

Secondly, the MEGA module is introduced into the model, which further improves the model's feature representation ability by fusing multi-scale features and applying a global attention mechanism. By weighting global information, the MEGA module helps the model better capture key seismic fault features during feature fusion. This design allows the model to focus not only on local details but also to fully utilize the global contextual information in 3D data, thereby enhancing the accuracy of fault detection.

After validation, the model achieved promising results in seismic fault detection tasks, automatically identifying and segmenting fault structures in seismic data. The accuracy was improved from 80% with the original 3D U-Net residual network to 85%-87%. This provides strong support for applications such as seismic exploration and subsurface imaging.

Keywords: Seismic Fault Detection, 3D U-Net, Convolutional Block Attention Module (CBAM), Multi-scale Enhanced Global Attention (MEGA), Deep Learning

How to cite: wang, Y.: Application of Optimized 3D U-Net Residual Network with CBAM and MEGA Modules in Seismic Fault Detection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1772, https://doi.org/10.5194/egusphere-egu25-1772, 2025.

This article mainly studies the characteristics of the earthquake sequence and the post - earthquake trend of the Ms6.4 earthquake in Yangbi, Yunnan，China on May 21, 2021. The research area is located in Yangbi Yi Autonomous County in the western part of Yunnan Province. The earthquake caused severe disasters such as housing destruction, traffic interruption, water conservancy facilities damage and power supply interruption. Through the analysis of the basic parameters of the earthquake, the tectonic stress environment and the seismogenic structure, it is determined that the earthquake is a right - lateral strike - slip rupture, with a focal depth of 8 kilometers, consistent with the direction of the Weixi - Qiaohou and Honghe fault zones. The earthquake sequence type is determined as the main shock - aftershock type (including the foreshock - main shock - aftershock type). Spatially, the source rupture expands unilaterally from the northwest to the southeast, mostly occurring in the upper crust high - speed zone or the high - low speed transition zone. Based on the G - R relationship and other analyses, the earthquake activity cycle in this area has active and quiet periods, and there are certain abnormal change laws before strong aftershocks, such as strain accumulation, calmness or enhancement of earthquakes above magnitude 3.5, and abnormal frequency of earthquakes above magnitude 2. The conclusion is that the earthquake sequence is normal, and the post - earthquake trend shows the characteristics of long - term calmness - breaking calmness - becoming calm again - signal earthquake (main shock). In the next few years, the strain accumulation may reach the peak and release. It is predicted that there may be a larger earthquake accompanied by strong aftershocks in 2025, or enter an active period with a strong aftershock magnitude exceeding 5.9 and lasting for more than half a year. Finally, the earthquake prevention and disaster reduction countermeasures are proposed.

How to cite: Wu, B.: The determination of the seismic sequence characteristics and post - earthquake trend of the Ms6.4 earthquake in Yangbi, Yunnan, China on May 21, 2021, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2519, https://doi.org/10.5194/egusphere-egu25-2519, 2025.

Seismic inversion in geophysics is a method that uses certain prior information, such as known geological laws and well logging and drilling data, to infer the physical parameters of underground media, such as wave impedance, velocity, and density, from seismic observation data, and thereby obtain the spatial structure and physical properties of underground strata. Seismic inversion is a highly complex problem with multiple solutions, and with the advancement of collection equipment, the volume of geophysical observation data is increasing at an astonishing rate. This presents new challenges for the accuracy and speed of seismic data inversion methods. There is an urgent need to develop intelligent and efficient inversion technologies for seismic inversion.

Deep learning networks have powerful nonlinear fitting capabilities and can be used to solve complex nonlinear problems, such as seismic inversion. However, the predictive ability of deep learning networks largely depends on the quantity of training data. In the early stages of oil and gas exploration and development, the amount of well logging label data available for training is very limited, which poses a challenge for the application of deep learning in seismic inversion. Semi-supervised learning seismic inversion methods consider both data mismatch issues and well logging data mismatch issues, and can better adapt to inversion problems in real-world scenarios. Unlike supervised learning approaches, semi-supervised learning does not require a large amount of labeled data, thus it can better handle situations of data scarcity or mismatch.

This paper utilizes a semi-supervised learning workflow to perform inversion on post-stack seismic data and has conducted experimental validation on the Marmousi 2 model. The experimental results show that, compared to supervised learning networks, the semi-supervised learning network still exhibits good predictive performance with a limited amount of data, demonstrating better stability in the presence of noise and geological variations, and effectively learns the mapping relationship between seismic data and artificial intelligence. Furthermore, as the amount of training data increases, the performance of the network also improves, confirming the importance of data quantity for training deep learning networks. The application results of the network on actual data indicate that the network has broad application prospects and feasibility. However, since the network is based on a channel-by-channel inversion method, there is still a lack of representation in terms of lateral continuity, which requires further exploration and improvement in subsequent research.

How to cite: zou, C., zhang, J., tang, B., and huang, Z.: Post stack inversion of seismic data based on Semi-supervised learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2973, https://doi.org/10.5194/egusphere-egu25-2973, 2025.

Seismic attribute analysis technology has been widely used in the prediction of fluvial reservoir sand body, but the traditional seismic attribute fusion technology based on linear model has low prediction accuracy and limited application range. This study focused on the non-linear fitting between seismic attributes and reservoir thickness, and used a variety of machine learning technologies to predict the fluvidal reservoir in Chengdao area of Dongying Sag (China).The channel sand body in Chengdao area is deep buried, thin in thickness, fast in velocity and affected by gray matter, so it is difficult to predict, which greatly restricts the oil and gas exploration in this area. In this study, on the basis of fine well earthquake calibration, several seismic attributes such as amplitude, frequency, phase, waveform and correlation are extracted and correlation analysis is done to remove redundant attributes. Then model training and parameter set optimization are carried out, thickness prediction is carried out with verification set, and vertical resolution is improved by logging reconstruction and waveform indication inversion. The results show that compared with the conventional support vector machine and back propagation neural network, the prediction accuracy of echo state network optimized by Sparrow algorithm is greatly improved. Based on the comprehensive prediction method of fluvial reservoir, three large channels developed in the lower part of Chengdao area and several small channels developed in the upper part of Chengdao area are effectively described. The research method can be used for reference to the similar complicated river facies prediction.

How to cite: Huang, Z. and Zhang, J.: Study and Case Application of Fluvial Reservoir Prediction Based on the Fusion of Seismic Attribute Analysis and Machine Learning Technologies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3391, https://doi.org/10.5194/egusphere-egu25-3391, 2025.

A strong earthquake with a magnitude of Mw 7.8 and a nearby epicenter in the city of Pedernales, Ecuador, occurred on April 16, 2016. This seismic event severely affected several cities in Ecuador, including Chone and Portoviejo, both in the Manabí province, located some 85 km and 150 km away from the hypocenter, respectively. In Chone, a total of 662 homes were damaged, while 2,678 collapsed dwellings were registered in Portoviejo, where 137 fatalities were reported. These, like most cities in the Manabí province, were built in narrow valleys over colluvial and alluvial soils.  The thickness of these sediments in contact with the rock is between 40 and 70 meters, which corresponds to both ancient and contemporary alluvial plains that are supported by alluvial-colluvial and alluvial valley-fill deposits. After the 2016 interplate subduction earthquake, the main co-seismic geological effects were reported for constructions built on these soils. Landslides were primarily documented in the colluvial soils, while soil liquefaction effects were reported in soft and loose soils. In this research, the influence of the presence of paleochannels in both cities, Chone and Portoviejo, on the liquefaction effects reported during the seismic event is analyzed.

The Chone River flows through Chone city from east to west, while its western part was modified after 1975, leaving an abandoned meander where the river channel was between 7 and 22 meters wide. The soil profile in this area demonstrates a low percentage of fines, ranging from 15 to 52%, with a relative density of about 50%, making it susceptible to liquefaction. After the 2016 earthquake, evidence of liquefaction effects was concentrated along the old meander. The Portoviejo River, which flows through the city of Portoviejo, has changed from a pronounced meandering shape in 1911 to its current form. This change spans about 4.5 km with a low slope between 0.1 and 0.2%. The width of the river has also been reduced, from 12 to 19 meters. The analysis of the liquefaction evidence indicates that the damage was very severe, especially in the constructions along the river.

The damage inventories performed in both cities have evidenced that paleochannels exhibited several signs of soil liquefaction. The geological and geotechnical conditions of these soils, such as size distribution, shallow groundwater table and recent-age deposits, may be considered as factors potentially increasing the probability of liquefaction. Therefore, a geomorphological study of the cities can help identify areas with a higher liquefaction potential.

How to cite: Pastor, J. L., Ortiz-Hernández, E., Toulkeridis, T., and Chunga, K.: Influence of paleochannels on liquefaction effects in the cities of Chone and Portoviejo (Ecuador) following the strong Pedernales earthquake in 2016, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3782, https://doi.org/10.5194/egusphere-egu25-3782, 2025.

This paper proposes a deep learning model based on 3D Convolutional Neural Networks (CNN) and a custom attention mechanism (ESSAttn) for seismic fault interpretation from 3D seismic data. The model combines the advantages of self-attention mechanisms and convolutional neural networks to enhance the ability to capture and represent features in three-dimensional seismic data. The core innovation of the model lies in the introduction of the ESSAttn layer, which applies a non-traditional normalization process to the input feature queries, keys, and values, thereby strengthening the relationships between features, especially in high-dimensional seismic data. Unlike traditional attention mechanisms, the ESSAttn layer normalizes feature vectors by squaring them and integrates features across depth, width, height, and channel dimensions, significantly improving the effectiveness of attention computation.

The model's role in seismic fault interpretation is reflected in several aspects. First, the 3D convolutional layers automatically extract spatial features from seismic data, accurately capturing the location and shape of faults. Second, the ESSAttn layer enhances critical region features and focuses attention on important areas such as fault zones, reducing the interference from background noise and significantly improving fault detection accuracy. Finally, by using a weighted binary cross-entropy loss function, the model can prioritize fault regions when handling imbalanced data, improving sensitivity to weak fault signals.

The network architecture consists of three main parts: encoding, attention enhancement, and decoding. Initially, two 3D convolutional layers and max-pooling layers are used for feature extraction and down-sampling, followed by the ESSAttn layer to enhance the extracted features. The decoding part restores spatial resolution through upsampling and convolution layers, ultimately outputting the fault prediction results. The model is trained using the Adam optimizer, with a learning rate set to 1e-4.

Experimental results show that the model performs well in seismic fault interpretation tasks, effectively extracting and enhancing fault-related features. It is particularly suitable for automatic fault identification and localization in complex geological environments. The model's automation of feature extraction and enhancement reduces manual intervention, increases analysis efficiency, and demonstrates strong adaptability to large-scale 3D seismic datasets. Furthermore, the model architecture was visualized and saved using visualization tools for easier analysis and presentation.

Keywords: 3D Convolutional Neural Networks, ESSAttn, Attention Mechanism, Fault Interpretation, Weighted Cross-Entropy, 3D Seismic Data, Deep Learning

How to cite: zhang, Y.: "Deep Learning Application for Seismic Fault Interpretation Based on 3D Convolutional Neural Networks and ESSAttn Attention Mechanism", EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4961, https://doi.org/10.5194/egusphere-egu25-4961, 2025.

How to cite: Motti, A.: Active and capable faults (FAC) and buildings in Norcia, interventions carried out and possibile technicolor and regulatory actions., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5076, https://doi.org/10.5194/egusphere-egu25-5076, 2025.

Coal seam floor water hazards, caused by stress changes resulting from coal mining, are a common type of mine water disaster, and their monitoring and prevention are critical for mine safety. The mine resistivity method, a geophysical exploration technique, is widely used for monitoring and detecting such water hazards due to its high sensitivity to water-bearing structures. In practical monitoring, it is necessary to rapidly and accurately invert apparent resistivity data. However, traditional linear inversion methods are prone to local optima, leading to biased results. In contrast, deep learning-based inversion methods utilize data mining to train networks, avoiding reliance on initial models and enabling fast computation of global optimal solutions.

This study constructs a multi-layer convolutional and skip-connected U-Net model to capture resistivity features at different scales. The model is trained and validated using synthetic data to evaluate its inversion accuracy and efficiency in monitoring coal seam floor water hazards. The results show that the U-Net-based inversion method can accurately identify low-resistivity anomalies associated with water hazards in the coal seam floor and quickly achieve the global optimal solution.

The method is further applied to the inversion of resistivity models with complex boundaries to simulate the impact of stress changes caused by coal mining on the formation of floor water hazards. The results demonstrate that this method is several times faster than traditional linear inversion methods, while maintaining high consistency with the actual model. Therefore, this inversion method provides an efficient new tool for monitoring coal seam floor water hazards and holds great promise for advancing technologies in mine water disaster prevention and geological exploration.

How to cite: Wang, H. and Hu, Y.: Research on mine electrical resistivity inversion method based on Deep Learning Method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5528, https://doi.org/10.5194/egusphere-egu25-5528, 2025.

The Himalayan region, shaped by the ongoing collision of the Indian and Eurasian tectonic plates, is one of Earth’s most seismically active and geologically complex areas. The Indian plate moves northeastward at a rate of approximately 5 cm per year, driving tectonic activity in this region. Understanding earthquake source mechanisms in this region is crucial for seismic hazard assessment and geodynamic studies. Moment tensor (MT) inversion, a widely used technique for analysing earthquake faulting mechanisms, matches synthetic waveforms to observed data by minimising the misfit. However, conventional 1D velocity models often fail to capture the region’s complex lateral heterogeneities, leading to inaccuracies in source characterisation. Synthetic waveforms, generated via Green’s functions using frequency waveform (FK) methods and 1D velocity models, are critical for MT solutions, with time shifts playing a pivotal role in achieving optimal waveform correlations.

This study employs a 3D velocity model to improve MT inversion for a Mw 3.5 earthquake on 9 January 2021 (30.76°N, 78.54°E). Green’s functions were generated using the spectral element method for six simulations. Each simulation resulted in three-component waveforms, with a total of 18 synthetics per station. Observed data from 24 broadband stations were analysed, and results were compared to those obtained using 1D models. Slight variations in strike, dip, and rake values underscore the limitations of 1D models in capturing Earth’s heterogeneities.

The study reveals that 3D velocity models significantly enhance MT solution accuracy, particularly in determining focal depths, faulting mechanisms, and seismic moment magnitudes. A probabilistic approach was also applied to quantify the uncertainty associated with MT estimates, providing confidence measures. Extending this approach, MT inversion was performed for another earthquake in the Uttarakhand Himalaya using the same 3D velocity model, further demonstrating the advantages of 3D wavefield simulations in seismically active regions.

Keywords: Himalayas, Moment Tensor, Green’s Function, Spectral element method.

How to cite: Maurya, S., Silwal, V., Mahanta, R., and Yadav, R.: Earthquake Moment Tensor Inversion Using 3D Velocity Model in the Himalayas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6545, https://doi.org/10.5194/egusphere-egu25-6545, 2025.

The effect of heterogeneity (dissimilar materials) and geometry constituting an interface is an important problem in earthquake source mechanics. These two parameters in the fault interface are responsible for complex rupture propagation and instabilities compared to the homogeneous planar interface. Here, a boundary integral spectral method (BISM) is proposed to capture the in-plane rupture propagation in the non-planar bi-material interface. The conventional traction BISM suffers from the disadvantages of hyper singularity and regularisation is needed (Sato et al., 2020; Romanet et al., 2020; Tada and Yamashita, 1997). So, we are utilising the representation equation arising from the displacement formulation devised by Kostrov (1966). It uses the elastodynamic space-time convolution of Green’s function and traction component at the interface. These displacement boundary integral equations (BIEs) are the inverse equivalent of traction BIEs. When applied to an interface between heterogeneous planar elastic half-spaces, these displacement BIEs have yielded simple and closed-form convolution kernels (Ranjith 2015; Ranjith 2022). Displacement BIEs of this kind have not been utilised to analyse fracture simulation for non-planar bi-material interfaces until now. We assume the small slope assumption (Romanet et al., 2024) in our formulation to get the required displacement BIEs. Also, we expand the displacement BIEs of a non-planar bi-material interface to the leading order to obtain the non-planarity effects. Finally, we present a general spectral boundary integral formulation for a non-planar bi-material interface independent of specific geometry and traction distribution in a small fault slope regime.

How to cite: Kumar, S. and Kunnath, R.: Boundary integral spectral formulation for in-plane rupture propagation at non-planar bi-material interfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8250, https://doi.org/10.5194/egusphere-egu25-8250, 2025.

In this study, we used the P-wave receiver functions (PRFs) to investigate the crustal structure of northern Morocco, located at the westernmost edge of the Mediterranean, near to the boundary between the African and Eurasian tectonic plates. This region is an integral part of the complex crustal deformation and tectonic system associated with the Alpine orogeny, characterized by concurrent compressional and extensional processes. These dynamics have led to the development of various structural and tectonic models aimed at explaining the area‘s geological evolution. The significant tectonic activity, evident in frequent seismic events, and complex lithospheric deformation, makes it an ideal location for studying crustal variations, lithospheric interactions, and mineralogical contrasts.

To achieve these objectives, we utilized high-quality seismic broadband data from the TopoIberia and Picasso seismic experiments, provided by the Scientific Institute, as well as from the broadband seismic stations operated by the National Center for Scientific and Technical Research (CNRST). The PRFs were extracted by decomposing teleseismic P-waves to isolate the effects of the local crustal structure. The dataset covers a wide range of regional stations, and the RFs provide detailed insights into crustal thickness, density and velocity contrasts, as well as deep discontinuities. Our preliminary results reveal significant variations in Moho depth, ranging from approximately 22.7 km in the eastern part of the region to 51.7 km in the western part. These variations correlate with changes in Vp/Vs and Poisson’s ratios, indicating mineralogical heterogeneity, with compositions spanning from mafic to felsic. These findings provide new constraints for tectonic models and enhance our understanding of the geodynamic processes involved, particularly the interactions between the crust and the upper mantle. This study not only improves our understanding of active tectonics and crustal composition in northern Morocco but also offers valuable insights for refining evolutionary models of the Western Mediterranean within its complex geodynamic context.

Keywords: Teleseismic event, P-wave, Receiver functions, Seismic Network, Vp/Vs ratio, Poisson ratio, Crustal structure, Mineralogical composition, Seismotectonics, Northern Morocco.

How to cite: Zakarya, H., El Moudnib, L., Badrane, S., Zeckra, M., and Lharti, S.: Continental Crustal Structure Beneath Northern Morocco Deduced from Teleseismic Receiver Function: Constraints into structure variation and compositional properties., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9078, https://doi.org/10.5194/egusphere-egu25-9078, 2025.

Here, we disentangle a complex disturbance deposit sequence attributed to the ~M 7 1873 CE Brookings earthquake from lower Acorn Woman Lake, Oregon, USA, using sedimentological techniques, computed tomography, and micro-X-ray fluorescence. The lower portion of the sequence is derived from schist bedrock and has characteristics similar to a local landslide deposit, but is present in all cores, suggesting that it is the result of high frequency (>5 Hz) ground motions from a crustal earthquake triggered the landslide. In contrast, the upper portion of the sequence is similar to a deposit attributed to the 1700 CE Cascadia subduction earthquake (two-sigma range of 1680-1780 CE): the base has a higher concentration of light-colored, watershed-sourced silt derived from the delta front followed by a long (2-5 cm) organic tail. The soft lake sediments are more likely to amplify the sustained lower frequency accelerations (<5 Hz) of subduction earthquakes, resulting in subaquatic slope failures of the delta front. The upper portion of the 1873 CE deposit, however, has an even higher concentration of watershed-sourced silt as compared to the 1700 CE deposit, which is suspected to be the result of shaking-induced liquefaction of the lake’s large subaerial delta. The tail of both the 1873 CE and 1700 CE deposits is explained as the result of flocculation that occurred during sustained shaking. A preliminary literature search suggests that flocculation may occur during low frequency (<4-5 Hz) water motion that is sustained for an extended period of time (~minutes). The subduction interpretation of the upper portion of the 1873 CE deposit is supported by the observation of a small local tsunami offshore and the presence of a possible seismogenic turbidite attributed to the 1873 CE Brookings earthquake in southern Oregon sediment cores.

These results are important to regional seismic hazards for several reasons. Southern Cascadia crustal earthquakes, not previously recognized as a threat in southern Oregon, have the potential to cause damage to infrastructure, including the Applegate dam and buildings and other structures at Oregon Caves National Monument. They also identify a previously unrecognized recent southern Cascadia subduction earthquake. Finally, the close temporal relationship between these two types of earthquakes, not observed elsewhere in the downcore record, may be early evidence of the transition of the Walker Lane belt into a transform fault as predicted.

How to cite: Morey, A. E., Shapley, M. D., Gavin, D. G., Goldfinger, C., and Nelson, A. R.: A complex deposit sequence from a small, southern Cascadia lake suggests a previously unrecognized subduction earthquake immediately followed a crustal earthquake in 1873 CE, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11849, https://doi.org/10.5194/egusphere-egu25-11849, 2025.

Local heterogeneities on a steadily propagating crack front create persistent disturbance along the crack front. These propagating modes are termed as crack front waves. There have been numerous investigations in the literature of the crack front wave associated with a Mode I crack (for e.g., Ramanathan and Fisher, 1997, Morrissey and Rice, 1998, Norris and Abrahams, 2007, Kolvin and Adda-Bedia, 2024). It has been shown that the Mode I crack front wave travels with a speed slightly less than the Rayleigh wave. However, similar investigation of the Mode II rupture has got minimal attention. Although, Willis (2004) demonstrated that for a Poisson solid, Mode II crack front waves do not exist for crack speeds less than 0.715, explicit results on the speed of the crack front waves, when they exist, have not been reported in the literature. The focus of the present work is on a numerical investigation using a recently developed spectral boundary integral equation method (Gupta and Ranjith, 2024) to obtain the speed of the Mode II crack front waves. Further, the perturbation formulae for Mode II crack, developed by Movchan and Willis (1995) are exploited to validate the numerical results on the crack front wave speeds.

How to cite: Mouli, Y. S. C. and Kunnath, R.: Crack front waves under Mode II rupture dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14737, https://doi.org/10.5194/egusphere-egu25-14737, 2025.

In Greece, almost all accelerometer stations provided accelerometer recordings, more than 400 in total, are characterized by inferred Vs30 values based on combination of surface geology and slope proxy (Stewart et al. 2014). However, only about 15% of them have been characterized by in-situ geophysical and geotechnical methods (invasive or/and non-invasive) were performed at a distance less than 100m from the station. In addition, regarding reference rock stations where shear wave velocity Vs30 is equal or greater than 800m/sec (engineering bedrock), only five (5) of them have been characterized todate, with respective values ranging between 800Vs301183m/s. It is evident that measured site characterization parameters of accelerometer stations in Greece is far from a desired goal, especially regarding those on rock reference sites. In this study multiple/combined non-invasive passive and active seismic techniques are applied in six (6) accelerometer stations throughout Greece, to improve earthquake site characterization metadat of the national accelerometer network, focusing on stations placed on geologic rock conditions. The Vsz (S-wave) and Vpz (P-wave) profiles and thereby Vs30 site class according to the Eurocode-8 are determined. In addition, to form a holistic picture of the site’s characterization, surface geology and topographic properties are provided for the investigated stations. Results of this study aim at contributing on improving site characterization parameters estimated by the Generalized Inversion Technique (source, path, site), as well as in defining Ground Motion Models for rock site conditions.

How to cite: Theodoulidis, N., Hollender, F., Rischette, P., Buscetti, M., Douste-bacque, I., Grendas, I., and Roumelioti, Z.: Characterization of selected “rock” reference stations of the Hellenic Accelerometer Network (HAN), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16647, https://doi.org/10.5194/egusphere-egu25-16647, 2025.

Ambient noise surface wave imaging has become a powerful tool for mapping subsurface velocity structures. Recent advancements in seismology, including the widespread deployment of high-density arrays such as nodal seismometers and Distributed Acoustic Sensing (DAS) systems, have facilitated the use of subarray-based methods for surface wave dispersion data extraction, such as phase-shift, F-K, and F-J methods. Alternatively, dispersion data can also be derived from two-station approaches, such as the FTAN method. However, integrating dispersion data extracted from subarrays and two-station methods remains challenging. In this study, we propose a joint inversion framework that combines these two types of surface wave dispersion data to achieve improved constraints on subsurface structures. We demonstrate its accuracy and practical applicability by conducting numerical experiments and applying the method to field data. The proposed approach introduces intrinsic spatial smoothing constraints. It effectively integrates subarray and two-station dispersion measurements, resulting in better imaging of subsurface shear-wave velocity structures compared to using either dataset alone. The versatility and potential of this method highlight its promising applications in a wide range of geophysical scenarios.

How to cite: Luo, S.: Joint inversion of surface wave dispersion data derived from subarrays and two-station methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20181, https://doi.org/10.5194/egusphere-egu25-20181, 2025.

The Sargur Schist Belt (SSB), the oldest supracrustal greenstone belt, present in the south-eastern part of the Western Dharwar Craton (WDC), is a ~ 320 km long N-S to NNE-SSW trending discontinuous belts that occurs as patches and pockets within the granitic‒gneissic complex. The SSB is mainly composed of metamafic, metaultramafic, metapelite, banded magnetite quartzite, micaceous quartzite, pyroxene granulite, amphibolite, hornblende-biotite schist/gneiss, etc. The schistose belt has undergone at least five deformations in which the last three are very prominent. The N-S trending high strain zones with S₄ mylonitic foliation were produced during the EDC-WDC accretion (D₄ deformation). The D₅ deformation (developed due to the accretion of the WDC to Southern Granulite Terrane (SGT) along the Moyar/Bavali Shear Zone (BSZ)) developed broad open folds/warps in the N-S trend of the SSB (as well as WDC) with E-W trending axial planes. On a regional scale, the D₃ fold axes curve into the WNW-striking BSZ (D₅ deformation), a steeply dipping transpressional shear zone with dextral kinematics.

The estimated metamorphic P-T conditions of 440-585 °C and 6.0-9.5 kbar in metapelites from north to south and 640-770 °C and 7-10 kbar in granulites present in south only. The grade of metamorphism varies from greenschist facies in the north to upper amphibolite to granulite facies in the south. The metapelite and pyroxene granulite shows a loading and slow cooling path. The top to the north movement along the BSZ thrusted the high-grade metapelites, mafic-ultramafic rocks and granulite facies rocks over the WDC lithologies. The higher grade of metamorphism along the southern part as compared to the rest of the WDC is due to its location close to the WDC-SGT accretion zone. The zircons from the metapelitic schist provided older age population ranging between 3.3-3.2, 3.1-3.0 Ga followed by 2.9-2.7 Ga and 2.55-2.4 Ga, whereas the granulites (2.5 and 2.4 Ga) and foliated granites (2.6 Ga) yielded only the younger age populations. However, the monazites in schistose rocks located along the northern part recorded the oldest ages up to 2.7 Ga followed by 2.4 and 2.2-2.1 Ga ages. The monazites from foliated granites, irrespective of their location, provided ages of 2.53, 2.36 and 2.24 Ga. However, the monazites in schists and granulites from the southern part provided younger ages of 0.77, 0.67, 0.53 Ga. The prominent 0.84, 0.76 and 0.62 Ga monazite ages obtained from the metapelites close to the BSZ suggests that the accretion along the BSZ initiated in Mid-Neoproterozoic and continued till Early-Paleozoic. 

How to cite: Swain, M. and Rekha, S.: Structure, metamorphism and geochronology of Archean Sargur Schist Belt, southern India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-941, https://doi.org/10.5194/egusphere-egu25-941, 2025.

This study analyses shear wave splitting measurements for core-refracted SKS and SKKS phases using data from nine strategically positioned seismic stations operated between 2023 to 2024 in the Central Indian Tectonic Zone (CITZ). The CITZ was formed during the mesoproterozoic orogeny in central India, resulting from the collision of the northern Bundelkhand Craton with a jumble of South Indian cratons (Dharwar, Bastar and Singhbhum Cratons). Understanding seismic anisotropy in this region is essential for elucidating mantle deformation patterns, which provides vital insights into geodynamic processes, lithospheric interactions, and ongoing tectonic activities shaping the CITZ. We employed both rotation-correlation and transverse energy minimisation techniques to determine the shear wave splitting parameters, namely the fast polarization directions (FPDs) and splitting delay times (δt). A total of 104 high-quality splitting measurements and 37 null measurements were obtained from 85 earthquakes (M ≥ 5.5) within epicentral distances of 84°-145° for SKS phases and 84°-180° for SKKS phases. The averaged δts at each seismic station ranges from 0.8 to 1.3 seconds, demonstrating significant anisotropy and heterogeneity in the upper mantle under the studied region. Our observations predominantly reveal NE-SW FPDs throughout the majority of stations, which correlate with the Absolute Plate Motion (APM) of the Indian plate. The discrepancies between FPDs and APM direction at some stations suggest the presence of fossilised anisotropic fabrics resulting from prior subduction events during mesoproterozoic. The smaller δt (0.8 sec) at the seismic station in the Pachmarhi region may be attributed to the significant magmatism during the cretaceous period. Null measurements, in conjunction with splitting measurements, suggest that the stations may be located in a region characterized by multi-layered or complex anisotropy. Our observations indicate that the mantle flow beneath the CITZ is influenced by the contemporary APM direction of the Indian plate as well as lithospheric frozen anisotropy.

How to cite: Bishoyi, N., Tiwari, A. K., and Dubey, A. K.: Mantle Deformation Pattern Beneath Central Indian Tectonic Zone: A Seismic Anisotropy Study in Satpura Gondwana Basin and Surrounding Areas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-964, https://doi.org/10.5194/egusphere-egu25-964, 2025.

A mineralogical study of early Cretaceous lamproite sill intrusions from the Raniganj Gondwana sedimentary basin in eastern India shows that apatite occurs as both phenocrystic and groundmass phase. Based on texture and compositional zoning patterns of apatite in lamproites from the Rajpura and Ramnagore collieries, three paragenetic stages of apatite are identified. Early-magmatic apatite (Ap-I), which forms the core of zoned grains, is Sr-rich–LREE-poor fluorapatite. This apatite underwent resorption prior to the growth of a second generation of magmatic fluorapatite (Ap-II). In Rajpura, Ap-II overgrowth rim is richer in Sr and LREE compared to Ap-I core. The increase in LREE is explained by the substitutions: (Na,K)⁺ + ∑LREE³⁺ = 2Ca²⁺, and [2∑LREE³⁺ + ₶ = 3Ca²⁺]. Ramnagore Ap-II overgrowth rim is oscillatory-zoned with fluctuations in Sr and LREE, which likely resulted from slow rate of diffusion of these elements relative to fast growth of crystals. Apatite of the third generation (Ap-III) forms the outermost rim of zoned grains and is marked by enrichment in Na, K and Ba. The substitutional schemes which explain the increase in Na and K from Ap-II to Ap-III are: (Na,K)⁺ + CO₃^2– = Sr²⁺ + PO₄^3– and [(Na,K)⁺ + (F,OH)^– = ₶ + ₶]. The role of carbonate in the former substitution is supported by high content of stoichiometrically calculated carbon (0.21–0.30 apfu) in Ap-III. The formation of Ap-III is attributed to metasomatic alteration of Ap-II by CO₂-bearing hydrothermal fluid and is associated with sodic metasomatism. Microporous texture has developed in Rajpura Ap-III which suggests a dissolution–reprecipitation mechanism for its development. This study demonstrates that compositional variations among different generations of apatite provide a meaningful record of melt evolution from early magmatic to magmatic-hydrothermal stages.

How to cite: Saini, J., Patel, S. C., and Kaur, G.: Apatite compositional constraints on the magmatic to hydrothermal evolution of lamproites from Raniganj Basin, eastern India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1988, https://doi.org/10.5194/egusphere-egu25-1988, 2025.

The Neoproterozoic western margin of the Yangtze Block in South China records significant continental crust-forming and modification processes through two distinct magmatic episodes. Using integrated geochemical and petrological approaches, we demonstrate that the 811-802 Ma Yuanmou Complex comprises alkaline high-Nb mafic rocks characterized by high Nb (15.7-41.9 ppm), TiO₂ (2.13-3.39 wt%) contents and positive ε_Nd(t) (+4.8 to +6.9), coupled with adakitic granodiorites showing high Sr/Y (17.4-49.0), (La/Yb)_N (16.3-52.6) and consistent bulk rock ε_Nd(t) (-0.5 to -1.5) and zircon ε_Hf(t) (0.0 to +2.3). The younger 750 Ma Jinping I-type granites exhibit high SiO₂ (71.2-73.5 wt%) and alkalis contents, enriched LREE patterns and depleted isotopic signatures (ε_Nd(t): -0.4 to +1.3; zircon ε_Hf(t): +4.83 to +8.37). Thermodynamic modeling reveals how crustal water content-controlled magma generation at different depths - low water-fluxed melting (2.0-3.5 wt% H₂O) produced I-type granites at medium pressure (6-9 kbar), while deeper settings with higher water content generated adakitic melts. The high-Nb mafic rocks in the Yuanmou Complex, derived from metasomatized mantle wedge, provide evidence for crustal-mantle interaction during back-arc extension. These coupled magmatic processes demonstrate how water content variations with depth influenced continental crust formation and evolution in arc settings.

How to cite: Huang, B., Wang, W., Zhao, J., Khattak, N. U., Li, R., Huang, S.-F., Lu, G.-M., Sun, L., Xue, E.-K., Zhang, Y., and Cai, X.-Y.: Water-fluxed melting and back-arc extension in the continental arc: Evidence from I-type granites, adakitic rocks and high-Nb mafic rocks at the western margin of the Yangtze Block, South China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7536, https://doi.org/10.5194/egusphere-egu25-7536, 2025.

A petrological and geochemical study was performed on 5 selected samples of peridotites from two different sites (Finero and Balmuccia) outcropping in the Ivrea Verbano Zone, with the aim to investigate the processes occurring in the deep lithosphere and the possible interaction with the lower crust.

The peridotites from Finero area fall in the harzuburgite (FIN1, FIN3, FIN4) field whereas those from Balmuccia are lherzolithes (BALM1) and werlhites (BALM4), highlighting respectively the presence of a more fertile and primordial mantle for two sites.

The rocks from Finero are featured by higher MgO (42-45.7 wt%) and lower Al₂O₃ (0.6-2.4 wt%), CaO (0.42-2.09 wt%) content with respect to Balmuccia (MgO: 39.6 wt%, Al₂O₃: 2.9 wt%; CaO: 2.8 wt%) as a consequence of their harzburgitic nature. They display an enrichment in large-ion lithophile elements (LILE), light rare earth elements (LREE, La_N/Yb_N:13.6) and depletion in high field strength elements (HFSE) differently from the Balmuccia peridotites, which are featured by a light depletion in LREE (La_N/Yb_N:0.4-0.8) and nearly flat HREE pattern. The LILE and LREE enrichment measured in the Finero peridotites could suggest that a portion of the mantle below Ivrea Verbano area was influenced by metasomatic fluids/melts. The BALM4 sample is characterized by anomalously low values of MgO (16.05 wt%) and high values of Al₂O₃ (16.3 wt%) and CaO (14.5 wt%), reflecting the high modal proportion of spinel.

Even the higher Sr (⁸⁶Sr/⁸⁷Sr= 0.70736-0.72571) and lower Nd (¹⁴³Nd/¹⁴⁴Nd=0.51236) isotopic values measured in selected mineral phases from Finero with respect to Balmuccia (⁸⁶Sr/⁸⁷Sr= 0.70268-0.70644; ¹⁴³Nd/¹⁴⁴Nd=0.51334) allow to speculate a relation with crustal fluids in the Finero mantle.

The composition of fluid inclusions entrapped in olivine and pyroxene crystals from Finero peridotites evidenced CH₄ and CH₄-N₂ associated with antigorite and magnesite whereas prevalent CH₄ associated with antigorite, magnesite and graphite was measured in the rocks from Balmuccia area. The origin of CH₄ could be related to synthesis via reduction of CO₂ by H₂ from internal/external serpentine to minerals or re-speciation of initial CO₂-H₂O fluids associated to graphite precipitation during cooling by obduction after orogeny; differently, the CH₄-N₂ fluids could be introduced by past subduction-related processes.

The isotopic helium (³He/⁴He ratio) varies between 0.08 and 0.17 Ra in the Finero peridotites and among 0.18 and 0.48 Ra in the Balmuccia ones, evidencing an isotopic difference between the two sites that cannot be explained by ⁴He radiogenic production. Differently, the Finero-Balmuccia variability could reflect the helium signature recorded in deep by subduction events and confirm the previous petrologic and geochemical evidences in favour of a metasomatised mantle by crustal fluids in the Finero area with respect to a more primordial in the Balmuccia one.

How to cite: Correale, A., Romano, P., Arienzo, I., Caracausi, A., Carnevale, G., Fazio, E., Mormone, A., Paonita, A., Piochi, M., Rotolo, S. G., and Zucali, M.: Two different mantle types as evidenced from a geochemical and petrological study of peridotites from the Ivrea-Verbano Zone , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8654, https://doi.org/10.5194/egusphere-egu25-8654, 2025.

The viscosity of silicate melts is one of the most important physical parameter governing natural processes such as volcanic eruptions, as well as manufacturing processes in the ceramic and glass industries. The traditional techniques for measuring viscosity are commonly time- and energy-consuming, they require equilibrium conditions, and are mostly limited to reduced viscosity intervals. Reducing testing time is a critical target for both academic and productive purposes. In order to calibrate an efficient tool capable of both reducing testing time and expand the range of viscosity determination, we used the hot stage microscope (HSM) technique. Specimens (pressed powders) of natural samples, previously measured employing a combination of concentric cylinder and the micropenetration dilatometric techniques, were heated at a rate of 10°C/min until melting. Characteristic shapes (Start sintering, End sintering, Softening, Sphere, Hemisphere, and Melting) were observed at characteristic temperatures (CT); then their viscosities were calculated from their known viscosity-temperature (Vogel-Fulcher-Tammann, VFT) relationships. The observed shapes result from a combined effect of viscosity and surface tension, allowing viscosity values at each CT to linearly scale with surface tension. Viscosity was calibrated by introducing correction factors based on glass chemistry. This approach provides two independent data sets – CT (from HSM) and the corresponding characteristic viscosity (from glass composition) – which can be used to calculate the VFT parameters. The comparison between calculated and experimental viscosity shows good correspondence, which significantly improved previous attempts using only HSM data. These results also highlight the potential of this non-contact technique for evaluating the effects of crystalline particles and porosity on the rheological properties of alumosilicate melts.

Contribution of PNRR M4C2 - PRIN 2022PXHTXM - STONE project, funded from EU within the Next generation EU program. CUP: D53D23004840006

How to cite: Giordano, D., Molinari, C., Dondi, M., Conte, S., and Zanelli, C.: A Method for Measuring Viscosity of Silicate Melts Using Hot Stage Microscopy (HSM), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8768, https://doi.org/10.5194/egusphere-egu25-8768, 2025.

Four multicomponent metaluminous glasses were designed to investigate the evolution of residual glass-ceramics comprising glass and crystals. Samples were obtained from melting of quartz-feldspars mixes (with varying Na/K ratio and silica content) further fast sintered at temperatures of 1200-1260°C. Using an integrated approach combining high- and low-frequency Raman spectroscopy and Differential Scanning Calorimetry (DSC), we characterized the viscous and elastic response of the residual glass and its role in the mechanical properties of the corresponding ceramic products.

High-frequency Raman spectroscopy allows for the analysis of Qn species, which represent the polymerization state of the glass network. Q⁰, Q¹, Q², Q³, and Q⁴ correspond to isolated tetrahedra, short chains, branched structures, and fully polymerized networks, respectively. This provides insights into how chemical composition affects the microscopic structure of the residual glass. Simultaneously, low-frequency Raman spectroscopy probes the boson peak, a signature of collective vibrational modes in the glass, which is directly linked to its elastic properties. By coupling the boson peak analysis with the elastic medium scaling law, we determine the vibrational density of states and shear modulus, key parameters for understanding the mechanical behavior of the system.

DSC measurements further enable the determination of critical thermal transitions of the glass, including the glass transition temperature, crystallization, and relaxation processes, which are essential for characterizing the viscous behavior of the residual glass. The integration of these techniques provides a comprehensive understanding of the role of residual glass in stress transfer and mechanical properties control within multicomponent ceramics.

This is a first insight on the characteristics of technologically relevant glasses for the production of porcelain and vitrified ceramic tiles. The approach here followed actually allows appreciating the effect of variations in the Na/K ratio and silica content that mirror what can occur in the industrial production. This paves the way for application in more complex materials and real industrial conditions.

Contribution of PNRR M4C2 - PRIN 2022PXHTXM - STONE project, funded from EU within the Next generation EU program. CUP: D53D23004840006

How to cite: Giordano, D., Cassetta, M., Conte, S., Zanelli, C., Molinari, C., Dondi, M., and La Felice, S.: Characterization of Residual Glass Evolution from Vitrified  Ceramics: Insights from Raman Spectroscopy and DSC into Viscous and Elastic Properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8978, https://doi.org/10.5194/egusphere-egu25-8978, 2025.

Investigating the main geochemical characteristics of the lower continental crust is essential to understand its formation and evolution, identifying crustal differentiation processes and possible crust-mantle interactions. We performed bulk rock (major and trace elements), noble gases isotopes (He, Ne, Ar), and fluid inclusions (Raman spectroscopy) analyses on metamorphic rocks from Ivrea-Verbano Zone (Southern Italian Alps). Specifically, we studied various lithologies (metapelite, metagabbro, mafic and felsic granulite, amphibolite, and gneiss) to analyse the continuous metamorphic gradient from amphibolite- to granulite-facies.

Bulk rock analyses confirm the mafic nature of the protoliths for metagabbros (MgO = 5.36-10.25 wt.%), mafic granulites (MgO = 8.32-25.80 wt.%) and amphibolite (MgO = 7.98 wt.%) plotting in the metabasite field of the ACF chemographic diagram. Felsic granulite and sillimanite-gneiss fall within metamorphosed quartz-feldspar rocks, except for metapelite, which approaches the metacarbonate field, due to the presence of secondary carbonates. Metagabbros, mafic granulites and amphibolite show low REE concentrations (∑REE between 3 and 25 ppm) and high Cr and Ni contents (up to 1865 and 265 ppm respectively in mafic granulite), reflecting the mafic/ultramafic nature of the protoliths, whereas felsic granulite, sillimanite-gneiss and metapelite show higher REE contents (∑REE between 48 and 197 ppm).

³He/⁴He isotope ratios in metamorphosed quartz-feldspar rocks (0.06-0.30 Ra) and metabasites (0.15 and 0.45 Ra) are significantly radiogenic, although the metabasites show slightly higher values, corroborating a more primitive component in their source. Most samples plot near the air component in the ²⁰Ne/²²Ne vs ²¹Ne/²²Ne diagram, except for mafic granulites which show a crustal-air mixing trend. As regards the Ar isotope ratios, all samples appear rich in radiogenic component (⁴⁰Ar/³⁶Ar up to 2645 in metagabbros).

Raman spectroscopy analyses on fluid inclusions in orthopyroxene from mafic granulites show the coexistence of talc, graphite and magnesite with methane, providing direct evidence of a complex history in terms of post-metamorphic reactions and P-T-fO₂ conditions.

Our preliminary results show the compositional diversity and evolution of the lower continental crust, highlighting the interplay between mafic and sedimentary sources and the importance of fluid interactions and post-metamorphic processes.

How to cite: Carnevale, G., Caracausi, A., Correale, A., Fazio, E., Paonita, A., Romano, P., and Zucali, M.: Geochemical characterisation of Permian lower continental crust: case study from Ivrea-Verbano Zone (NW Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9306, https://doi.org/10.5194/egusphere-egu25-9306, 2025.

Experimental data on rock physical properties obtained through laboratory methods are enhanced by advanced techniques like X-ray microtomography (µCT) and image analysis. Lava rocks are important geological formations worldwide with varying textures, structures, and physical and mechanical behaviour. This research focuses on the heterogeneity analysis of vesicular lava rocks with intermediate composition from the Fogo Volcano (or Água de Pau Volcano, S. Miguel, Azores, Portugal). The effective porosity of six cubic samples is determined using the buoyancy technique. Ultrasonic wave velocities and capillarity absorption coefficient are obtained along three orthogonal directions using the through-transmission method and a European standard, respectively. Unconfined compressive strength (UCS) combined with µCT is determined in three cores from a single cube.

Results demonstrate that pore structure governs water uptake by capillarity and ultrasonic wave velocities. Regardless of the direction, the nonlinear water imbibition reflects a bimodal pore size distribution, confirmed through µCT imaging. The Sharp Front model describes this behaviour as the sum of two separate absorption processes related to larger (28.01-12.96 g/m²·s^0.5) and finer (0.45-1.73 g/m²·s^0.5) pores. Capillary-connected porosity (5.07%) is lower than connected porosity (18.5–20.1%) since gravitational fluid transport dominates for large pores (>1 mm). P-wave velocities (2802–3208 m/s) show minor dependence on pore shape, while Vp/Vs ratios (1.76 ± 0.25), dynamic Young’s modulus (16.78 ± 3.20 GPa), and Poisson’s ratio (0.23 ± 0.11) reflect vesicular textures.

µCT-based image analysis enables porosity quantification, revealing that effective porosity includes vesicles and pore-linking fractures. Permeability (0.7–6.6 mD) depends on tortuosity, which reduces fluid percolation despite higher connected porosity.

UCS (15.5-36 MPa) variations depend on pore size, orientation relative to the loading direction, and connected porosity, with minor influence from pore shape. µCT imaging reveals failure through tensile splitting, with fractures propagating from pore edges in all cores. The weakest specimen has more plagioclase phenocrysts, whose borders, intragranular cracks, and pores contribute to reduced strength.

These findings underscore the need to consider the heterogeneous pore structure of vesicular lavas when interpreting field measurements or improving volcano stability models. Advanced imaging and computational techniques clarify the role of vesicles and phenocrysts in strength and crack development patterns, providing important insights into the mechanics of lava rocks.

How to cite: Pereira, M. L., Cueto, N., Pappalardo, L., Buono, G., Falasconi, A., Moreira, M., Zanon, V., and Fernandes, I.: Characterisation of the heterogeneity of vesicular lava rocks from Fogo Volcano (Azores, Portugal) combining conventional laboratory methods with X-ray microtomography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9505, https://doi.org/10.5194/egusphere-egu25-9505, 2025.

In the last decades, the volcanically active Aeolian Islands have been the focus of numerous geochemical investigations and monitoring activities, primarily focused on the islands of Vulcano, Stromboli and Panarea. However, relatively few studies have explored the geochemical characteristics of other islands, despite evidence of hydrothermal activity. Salina, for instance, hosts a shallow, cold, low-salinity aquifer that overlies a deeper warmer aquifer, with highly saline water. Additional noteworthy features include hydrothermal deposits on the seafloor and offshore submarine gas emissions. Similarly, Lipari hosts a thermal aquifer (e.g. Terme di San Calogero) and exhibits significant hydrothermal emissions along its western coast, particularly in areas of Valle del Fuardo and Caolino quarry. In this study we conducted detailed geochemical surveys on Lipari and Salina to investigate the origins of the fluids and their relationship with the geodynamic framework. The research is part of the Project CAVEAT (Central-southern Aeolian islands: Volcanism and tEArIng in the Tyrrhenian subduction system), which aims to provide a comprehensive understanding of the current geodynamics in the southern Tyrrhenian region, focusing on the interaction between volcanism and tectonic activity within the Tyrrhenian subduction system.

On Salina and Lipari islands, soil CO₂ flux measurement campaigns were conducted to examine the spatial distribution of soil CO₂ emissions. Thermal surveys using an Unmanned Aircraft System were conducted over fumarolic areas to detect thermal anomalies associated with zones of preferential fluid emissions. These measurements helped define preferential pathways for fluid migration and identify active tectonic structures associated with areas of elevated soil CO₂ emissions. At selected sites, isotopic composition of gas was analyzed to infer the gas origins. On Lipari, soil CO₂ emission anomalies revealed a NNW-SSE alignment consistent with the area’s primary tectonic structures. Isotopic analysis confirmed a contribution of deep-origin fluids to these emissions. Thermal (up to 45.8 °C) and cold waters from Salina and Lipari were sampled and analyzed for their chemical and isotopic composition, as well as for dissolved gases. The isotopic composition of the water clearly indicates that the sampled groundwater originates from a mix of meteoric water and seawater, with varying degrees of mixing at each site. Gases dissolved in water exhibit an atmospheric component with a high content of CO₂ in the most brackish samples. At Salina, the isotopic composition of dissolved helium reflects a mantle contribution. Collectively, the findings emphasize the significant influence of mantle and deep-origin origin fluids in shaping the geochemistry of both islands. They further highlight the critical role of geodynamic and tectonic processes in governing fluid emissions across the two islands.

How to cite: Camarda, M., De Gregorio, S., Liotta, M., Di Martino, R. M. R., Oliveri, Y., Palano, M., Pisciotta, A., Riolo, G. M., and Romano, P.: Unveiling the geochemistry of fluids in the Central Aeolian Islands (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10890, https://doi.org/10.5194/egusphere-egu25-10890, 2025.

During active-source 2D marine ocean bottom seismic exploration, significant deviations of shot lines from the designed survey lines can introduce errors in 2D structural models, particularly in areas with rough bathymetry, such as mid-ocean ridges. By employing 3D tomography, it is possible to construct a three-dimensional model of the survey area that incorporates the actual shot locations and Ocean Bottom Seismometer (OBS) positions, leading to more accurate velocity structure models.

In 2021, the Joint Arctic Scientific Mid-Ocean Ridge Insight Expedition (JASMInE) acquired high-quality OBS data from the Gakkel Ridge in the Arctic Ocean. However, due to the presence of dense floating ice, significant offsets occurred between the shot lines and the OBS station profiles. Consequently, applying a 3D tomography-based modeling approach is essential for imaging the velocity structure in this region.

This study utilized the JIVE3D software to develop a 3D P-wave velocity model along a profile perpendicular to the 85°E spreading axis of the Gakkel Ridge, based on high-resolution multibeam bathymetry data. Compared to the velocity structure derived from 2D modeling, the P-wave velocities beneath the spreading axis are found to be lower in the 3D model, while lateral velocity variations in the upper oceanic crust are more pronounced away from the spreading axis. Despite these differences, the overall velocity structure and crustal thickness trends are consistent, indirectly validating the reliability of the 2D structural model.

Based on this 2D P-wave model, with data of 1257 S-wave arrival times picked from 9 OBS stations along the profile perpendicular to the mid-ocean ridge, using a forward modeling trial-and-error approach, a preliminary Poisson’s ratio structure beneath the profile was obtained. The Poisson’s ratio in Layer 2 of the oceanic crust ranges from 0.36 to 0.40, with relatively lower values beneath the spreading axis. In Layer 3, the Poisson’s ratio varies from 0.28 to 0.38. The relatively higher Poisson’s ratio values may indicate the presence of abundant fractures or fluids within the oceanic crust in this region.

How to cite: Niu, X., Li, J., Yang, W., Yu, J., Ding, W., and Zhang, T.: Poisson’s ratio structure and three-dimensional P wave velocity structure beneath the profile across the Gakkel ridge 85°E axis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11736, https://doi.org/10.5194/egusphere-egu25-11736, 2025.

Natural CO₂ emissions play a crucial role in understanding global CO₂ budget estimates. Consequently, numerous studies have focused on CO₂ emissions across various regions worldwide. However, the majority of these investigations have concentrated on terrestrial CO₂ emissions, with relatively fewer studies exploring submarine CO₂ emissions. Moreover, almost all the studies have focused on areas with significant hydrothermal activity, particularly those along Mid-Oceanic Ridges, while shallow-water hydrothermal vents have received comparatively little attention. Furthermore, diffuse submarine gas emissions, lacking or with little visible surface evidence, remain largely unexplored. This study investigates the CO₂ emissions in the shallow submarine environment around the coast of the Island of Vulcano (Aeolian Islands, Italy) by measuring dissolved CO₂ concentrations. Vulcano, has been characterized by an intense hydrothermal activity since its last eruption from La Fossa cone (1888-­1890). Vulcano features several fumarole fields, including one on the northern crater rim of La Fossa cone and another near the sea in the northeastern sector. Additionally, significant soil CO₂ degassing occurs across the volcanic edifice. In the Vulcano Porto area, numerous thermal wells discharge fluids with temperatures reaching up to 80 °C. Submarine emission areas are visible, at shallow depths, close to the beaches in the southern and northeastern sectors. Measurements of dissolved CO₂ concentrations were conducted along seashores and rocky coastlines and in sites encompassing both visible and non-visible emissions. In the northeastern sector, measurements focused on the area between the Vulcanello peninsula and the northern slopes of the volcanic cone. The northernmost section of this area, extending to the Faraglione cone, is widely recognized in the literature as Baia di Levante (BL), a well-documented site of significant CO₂-dominant hydrothermal fluids discharge, trough submarine vents placed on the seafloor, at shallow depth, near the shoreline. In this area, we performed measurements along the beach at depth of about 50 cm below sea surface. The measured values remain elevated throughout the entire profile, consistently surpassing those of seawater in equilibrium with the atmosphere (ASSW). Concentrations peaked near visible bubbling zones, with concentration values ​​that exceeded the 20%. Moving southward, between the port dock and the crater slopes, measurements were conducted both close to the coastline and approximately 30 meters off the coast. In this area, sporadic bubble emissions from the seafloor were observed and the concentration of dissolved CO₂ decreases significantly compared to the BL area. However, the dissolved CO₂ concentration remain elevated, above those expected for ASSW. Along the eastern coast, measurements were performed in two selected sites along the rocky coastlines. Anomalous dissolved CO₂ concentrations, reaching up to 1400 ppm, were recorded also in these areas. In the southern sector, measurements were taken along Gelso beach. CO₂ concentrations were consistently high along the entire beach profile. The results indicate that submarine CO₂ emissions are not confined to areas with visible surface evidence, but also occur in areas with minimal or no-visible hydrothermal activity.

How to cite: De Gregorio, S., Camarda, M., Cappuzzo, S., Francofonte, V., and Pisciotta, A.: Investigations on the shallow submarine CO2 emissions around the Island of Vulcano (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11968, https://doi.org/10.5194/egusphere-egu25-11968, 2025.

Correlating surface hotspot volcanism with sharply defined edges of Large Low Shear Velocity Provinces (LLSVPs) is a common yet potentially oversimplified approach in mantle geodynamics. Such direct radial projections ignore the lateral displacement of plume conduits observed in seismic tomographic imaging, which suggests that purely vertical transport through the mantle is not guaranteed. Furthermore, many studies merge the African and Pacific LLSVPs, despite evidence that their correlation with hotspots differs significantly. These oversimplifications can lead to misinterpretations of plume-lithosphere interactions, the interaction between mantle plumes and the ambient ”mantle wind”, and mantle flow dynamics in general. Here, we systematically investigate how varied criteria can alter the inferred hotspot– LLSVP edge relationship. We separately analyze African and Pacific LLSVPs using: multiple tomography models, horizontal-gradient based definitions of edges, different vote-map methodologies, and distinct plume geometry assumptions–from perfectly vertical “spokes” to randomly deflected trajectories. We also apply the Back-and-Forth Nudging (BFN) method applied to time-reversed thermal convection, initialized with a present-day seismic–geodynamic–mineral physics model (Glisovic & Forte, 2016), to provide a geodynamically consistent assessment of the relationship between present-day hotspot locations and their source regions in the deep lower mantle. This independent geodynamic assessment clarifies how arbitrary choices concerning the interpretation of hotspots and LLSVP edges may lead to biased or skewed deep-plume reconstructions. Our results reveal that adjustments in hotspot catalogs, or the decision to combine the two main LLSVPs rather than regard each as dynamically distinct, can yield important differences in the significance attributed to sharply defined LLSVP edges. These findings underscore that commonly cited correlations between hotspot locations and LLSVP boundaries hinge on assumptions that vary considerably across the literature. Recognizing and rigorously defining input parameters–particularly the separate treatment of the African and Pacific LLSVPs and the inclusion of realistic lateral plume deflection–proves essential for robust interpretations of deep Earth structure. This highlights the need for standardized methodologies and careful parameter choices to avoid overstating the importance of LLSVP edges in shaping plume pathways.

How to cite: Johnston, G., Liu, S., Forte, A., and Glisovic, P.: Playing with Edges: The Influence of Arbitrary Definitions on Hotspot–LLSVP Correlations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14815, https://doi.org/10.5194/egusphere-egu25-14815, 2025.

The 2023-2024 eruptions at Sundhnúksgígar in Iceland produced tholeiitic basaltic lavas that traveled at high velocities, affecting vast areas. In this context, disequilibrium crystallization can play a fundamental role in modulating the lava flow dynamic and inundation capacity. To investigate this phenomenon, we performed a comprehensive rheological characterization of the Sundhnúksgígar basaltic liquid and crystal-bearing suspension under both disequilibrium and near-equilibrium conditions. Compared to other basalts erupted worldwide, our results reveal unique features of the Sundhnúksgígar melt: i) exceptionally low solidification rates and ii) the ability to crystallize even at the highest cooling rates applied during the experiments. These characteristics enhance the efficiency of external crust formation, minimizing heat loss from the inner portion of the lava flow, which consequently experiences slower cooling rates. As a result, the lava is able to flow for longer times and travel greater distances than other basaltic flows. Our findings underscore the critical influence of disequilibrium crystallization on the rheological evolution and emplacement behavior of basaltic lavas, with implications for hazard assessment and risk mitigation during effusive eruptions.

How to cite: Di Fiore, F., Vona, A., Di Genova, D., Caracciolo, A., Pontesilli, A., Calabro', L., Giuliani, G., Mollo, S., Bondar, D., Nazzari, M., Romano, C., and Scarlato, P.: Impact of Cooling Rate on Rheology and Emplacement Dynamics of Basaltic Lava Flows: Insights from the 2023-2024 Sundhnúksgígar Eruption (Iceland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17683, https://doi.org/10.5194/egusphere-egu25-17683, 2025.

This study focuses on characterizing seismogenic zones by establishing a interrelationship between electrical and elastic properties using Effective Medium Theories (EMTs). The seismogenic zones exhibit complex geological and geophysical signatures that can be explored through joint analysis of electrical resistivity and elastic moduli. The research applies EMTs such as Self-Consistent Approximation (SCA), Generalized Effective Medium (GEM), and Differential Effective Medium (DEM) to model the physical properties of rocks under varying conditions of pressure, porosity, and fluid saturation.

The study compares theoretical predictions with observed data to understand how resistivity, influenced by fluid connectivity and composition, correlates with elastic properties, which are sensitive to stress and fracture networks. The study can reveal critical insights into the mechanical and fluid characteristics of seismogenic zones. By integrating theoretical models with available geophysical data, this work provides a framework for analyzing the interdependence of electrical and elastic properties in seismogenic regions. The findings contribute to advancing the understanding of fluid dynamics, and rock deformation in seismogenic zones, offering a valuable tool for seismic hazard assessment and monitoring.

How to cite: Raju, K. and Siniscalchi, A.: Interrelationship between the electrical and elastic properties using effective medium theories, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17921, https://doi.org/10.5194/egusphere-egu25-17921, 2025.

The Istituto Nazionale di Geofisica e Vulcanologia - Osservatorio Etneo (INGV-OE) is in charge to monitor Mt. Etna (Catania, Italy), one of the most active volcanoes in Europe. Its activity is characterised by mild strombolian to powerful lava fountains. Monitoring active volcanoes is fundamental to reduce the volcanic hazard, in particular in dense populated areas as it is the case for the Mt. Etna [1]. The combination of different remote sensing systems can improve the analysis of Etna volcanic activity and give a more reliable quantification of volcanic source parameters as the Cloud Height, Mass Eruption Rate, Fine ash Mass and Particle Size. Volcanic source parameters are used as input parameters by volcanic ash transport and dispersal model. A more accurate estimate of these parameters reduces the uncertainty of numerical dispersal model simulations. The data used for this study come from different sources: The VIVOTEK IP8172P is a visible camera located in Catania. The second is a Thermal-Infrared camera located in Nicolosi that collects images (320 x 240 pixels) at few meters resolution [2] [3]. The third instrument is a X-band (9.6 GHz) polarimetric weather radar located nearby the International Airport Vincenzo Bellini (Catania). The fourth is the Spinning Enhanced Visible and Infrared Imager onboard the Meteosat Second Generation Geostationary Satellite [4]. Through the use of complementary remote sensing systems, we aim at improving our understating of explosive phenomena at Etna volcano.

[1] Bonadonna, C., Folch, A., Loughlin, S., & Puempel, H. (2012). Future developments in modelling and monitoring of volcanic ash clouds: outcomes from the first iavcei-wmo workshop on ash dispersal forecast and civil aviation. Bulletin of volcanology, 74 , 1–10.

[2] S. Scollo, M. Prestifilippo, E. Pecora, S. Corradini, L. Merucci, G. Spata, et al., "Eruption column height estimation of the 2011–2013 Etna lava fountains", Ann. Geophys., pp. 57, 2014.

 [3] S. Calvari, G.G. Salerno, L. Spampinato, M. Gouhier, A. La Spina, E. Pecora, et al., "An unloading foam model to constrain Etna’s 11–13 January 2011 lava fountaining episode", J. Geophys. Res. Solid Earth, vol. 116, pp. B11207, 2011.

[4] S. Scollo, M. Prestifilippo, C. Bonadonna, R. Cioni, S. Corradini, W. Degruyter, et al., "Near-Real-Time Tephra Fallout Assessment at Mt. Etna Italy", Remote Sens., vol. 11, pp. 2987, 2019.

How to cite: Romeo, F., Mereu, L., Prestifilippo, M., and Scollo, S.: Etna volcano monitoring by remote sensing systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20022, https://doi.org/10.5194/egusphere-egu25-20022, 2025.

Deception Island, the most active volcanic system in the South Shetland Islands (Antarctica), has recorded over 20 explosive monogenetic eruptions in the past two centuries. The island’s most recent eruption in 1970 was one of its most violent, with a Volcanic Explosivity Index (VEI) of 3. This event generated a column height of up to 10 km and produced an estimated bulk eruptive volume exceeding 0.1 km³, with tephra fallout recorded over 150 km away on King George Island. To investigate the magmatic processes leading up to this significant eruption, we conducted detailed geochemical and textural analyses of near-vent pyroclastic deposits and distal tephra fall-out layers preserved in Livingston Island’s glaciers. Near-vent deposits include dilute pyroclastic density currents (PDCs) and lithic-rich breccias. Olivine crystals in these deposits exhibit two distinct populations: low-forsterite (Fo_65–70 mol.%) and high-forsterite (Fo_80–85 mol.%), with similar CaO contents (0.1–0.5 wt.%) but varying NiO concentrations (0–0.4 wt.% in low Fo; 0.02–0.10 wt.% in high Fo). Pyroxene microanalyses also reveal two distinct populations: i) augite-diopside (En_45–50, Fs_5–25, Wo_38–50) and ii) enstatite (En₉₀, Fs₁₀, Wo₀). Augite-diopside crystals can be further subdivided based on their Mg# (Mg# = Mg/(Mg+Fe) x 100) and TiO₂ contents. The first group shows Mg# values between 80–85 mol.% and TiO₂ ranging from 0.5 to 3.0 wt.%, while the second group displays Mg# values of 55–70 mol.% and narrower TiO₂ concentrations (0.5–1.25 wt.%). Notably, the enstatite population was not found in distal tephra layers. Plagioclase crystals range in composition from Bytownite to Andesine (An_85–40 mol.%). Comparative analyses with distal tephra layers confirm the presence of both olivine populations and overlapping augite-diopside compositions but lack enstatite. Plagioclase compositions show consistency between near-vent and distal deposits. These findings align the 1970 eruption deposits with compositional trends observed in other post-caldera collapse eruptions, shedding light on the island's eruptive history and magmatic evolution.

This work has been partially financed by the grant PID2023-151693NA-I00 funded by MCIN/AEI/10.13039/501100011033.This work is part of the CSIC Interdisciplinary Thematic Platform (PTI) Polar zone Observatory (PTIPOLARCSIC) activities. This research was partially funded by the MINECO VOLCLIMA (CGL2015-72629-EXP) and HYDROCAL (PID2020-114876GB-I00) MICIU/AEI/10.13039/501100011033 research project. Sampling was founded by CICYT (ANT91-1270, ANT93-0852 and ANT96-0734) and MICINN grant CTM2011-13578-E.

How to cite: Albert, H., Ruiz, J. L., Hopfenblatt, J., Pedrazzi, D., Geyer, A., Aulinas, M., Polo-Sánchez, A., Álvarez-Valero, A. M., and Vilanova, O.: Magmatic processes driving the 1970 eruption on Deception Island, (Antarctica), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20055, https://doi.org/10.5194/egusphere-egu25-20055, 2025.

Vulcano Island in Aeolian Archipelago last erupted in 1888-1890 and since then it is affected by an intense fumarolic activity from both the summit crater area of La Fossa volcano and by the hydrothermal system of Baia di Levante located very near to the main settlement of Vulcano Porto.  Ordinary solfataric activity is periodically interrupted by unrest crisis at La Fossa crater associated with increase in fumarole temperature and output, anomalous seismicity, ground deformation and accompanied by an increase in diffuse soil CO₂ degassing at Vulcano Porto. In Autumn 2021 a new major unrest crisis began exposing to a high gas hazard Vulcano Porto settlement due to contemporary dispersion of crater fumarolic plume and diffuse soil CO₂ degassing; Starting from February 2022, with apex in May, a huge increase in gas output of the geothermal system of Levante Bay was observed. The Baia di Levante area is characterized by the presence of a low-temperature fumarolic field (<100°C) either onshore and offshore and fed by a shallow hydrothermal aquifer heated by magmatic gases. A wide diffuse soil CO₂ degassing area extends all over the main beach. The chemical composition of bubbling gases is CO₂-dominant, associated with a 1-3 vol.% of H₂S and minor CH₄ and H₂. The Bay is one of the main sites of attraction for the thousands of tourists who visit the island and given the increased risk for gas emissions and possible phreatic eruptions (due to overpressuration of the geothermal aquifer) we carried out some extraordinary geochemical surveys. These consisted of (i) estimation of diffuse soil CO₂ flux over a target area (154 points over 16,750 m²) established since 2004; (ii) estimation of the convective CO₂ and H₂S flux (the main hazardous gases) from the onshore (50 points in the Mud Pool and surrounding areas) and offshore gas vents (2 main large vents and 60 small vents); (iii) Repeated measurements of the chemico-physical parameters (temperature, pH, Eh, conductivity and dissolved O₂) in the Baia di Levante sea water (107 profiles; water depth from 50cm to 12m). In particular we investigated the areas characterized by the presence of whitish waters, trains of gas bubbles, emissive vents. Results shown significantly increased values ​​compared to the past of the total CO₂ and H₂S output (diffuse and convective) measured on land and at sea surface. The sea water shows the presence of a wide anomalous pH in the near-shore sector between Faraglione and Vent 1 and to a lesser extent to the N of the bay. A wide anomaly of negative Eh values ​​persist at all depths in almost all of the bay. A huge emissions of acid gases from the increased submarine fumaroles alter the chemical-physical parameters of the sea water along the bay. Considering the increased gas hazard the adoption of risk prevention measures was suggested to authorities.

How to cite: Ranaldi, M., Carapezza, M. L., Tarchini, L., Pagliuca, N. M., Pruiti, L., and Sortino, F.: Gas hazard assessment at the hydrothermal system of Baia di Levante at Vulcano Island during the 2021-23 unrest of La Fossa crater (Aeolian Islands, Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20387, https://doi.org/10.5194/egusphere-egu25-20387, 2025.

Natural microseismicity serves as a potent tool for exploring smaller-scale hydrothermal and tectonic phenomena. Investigating seismic activities within the hydrothermal fields of mid-ocean ridges(MORs) offers profound insights into earth's internal dynamics. However, studies on natural earthquakes at ultra-slow spreading ridges, especially the Southwest Indian Ridge (SWIR), remain relatively scarce. To investigate the microseismic distribution, heat flow pathways, and tectonic characteristics of the Longqi hydrothermal field, a typical representative of SWIR, this paper processed one month of passive source OBS data from the DY43 cruise through microearthquake detection and relocation, obtaining a catalog of over 3000 earthquakes, significantly expanding the earthquake database for the Longqi field and improving the magnitude completeness. And the b-value calculation and imaging of the earthquake catalog were carried out using the maximum likelihood method and grid search method, respectively. The research results indicate that: ① The overall b-value of the SWIR Longqi field is 0.989; ② The b-value at the center of the Longqi hydrothermal vent is approximately 0.8, while the b-value around the vent is around 1.2; ③ High and low b-value areas alternate at a depth of 10km along the ridge axis; ④ There is an anomalously low b-value area of around 0.5 at depths of 12-16 km to the north across the ridge axis. Combining previous research results on b-values at MORs, this paper suggests that the background b-value of less than 1 in the Longqi field is consistent with its tectonic-type hydrothermal origin. The detachment fault beneath the Longqi hydrothermal vent leads to high stress and a low b-value, while the microseismic activity around the vent originates from rock fracturing caused by the combined effects of cold seawater and hydrothermal fluids. The uneven distribution of high and low b-values in the deep part of the hydrothermal field may reflect the uneven distribution of subsurface magma. The low b-value area in the north is speculated to be due to high stress resulting from torsional compression at the bottom of the detachment fault. In summary, it can be anticipated that the spatial distribution of b-values will serve as an indicator and reference factor for stress, fault structure, and magmatic-hydrothermal activity in MOR hydrothermal field in the future.

How to cite: wang, K.: Spatial distribution of b-values for microseismicity in the SWIR Longqi hydrothermal field and magmatic-tectonic interpretation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20441, https://doi.org/10.5194/egusphere-egu25-20441, 2025.

Transform faults are often considered to be geometrically simple, nearly linear, vertical structures that localize crustal deformation within a narrow zone surrounding the fault. The deformation kinematics are typically purely strike-slip, parallel to far-field plate motion, with seismic slip above the brittle-ductile transition, near the 600 °C isotherm, which is well predicted by thermal models. Although deviations from these simplified features have been described, much remains to be learned about the seismogenic behavior of transform faults, for example, why they release much less seismic moment than predicted by plate motion models, or why they so rarely produce earthquakes of magnitudes as large as would be expected given their geometric segmentation (>M7). 

The Oriente Transform Fault (OTF) along the southern margin of eastern Cuba, at the boundary between the Caribbean and North American plates, is a particularly relevant example to inform on the seismogenic behavior of transform faults for at least 5 reasons: (1) the OTF geometry changes from a nearly continuous trace along the Cayman Ridge to a highly segmented one westward along eastern Cuba, (2) the geometrically continuous segment was the location of a magnitude 7.8 supershear earthquake in January 2020, (3) GNSS-derived strain measurements indicate that this segmentation variation corresponds to a transition from very shallow (<5 km) mechanical coupling —perhaps creep— of the fault, to complete coupling across the entire crustal thickness (20 km), (4) earthquake hypocenters offshore eastern Cuba locally reach subcrustal depths, (5) earthquake focal mechanisms and offshore geological observations show fault-normal compressional deformation along this purely strike-slip segment.

Here we revisit the offshore trace and seismotectonics of the OTF in light of recent data. We benefit from several oceanographic campaigns in the northern Caribbean, in particular the recent Haiti-TWIST campaign of the Pourquoi Pas? R/V, during which new high-resolution bathymetric and seismic reflection data were acquired, filling several important gaps. We also benefit from recent deformation results from GNSS measurements in Cuba, as well as a new compilation of earthquake moment tensor solutions.

How to cite: Calais, E., Leroy, S., Poort, J., Lebrun, J.-F., Mercier de Lépinay, B., Gonzalez, O., Moreno, B., Granja-Bruna, J.-L., Roest, W., Marcaillou, B., Aiken, C., and Klingelhoefer, F.: Seismotectonics of the Oriente Transform Fault revisited, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20933, https://doi.org/10.5194/egusphere-egu25-20933, 2025.

Subduction zones represent more than half of the total plate boundaries length (38,000 over 64,000km) and cause fast geographic changes by a range of geological processes occurring at local to regional scales such as crustal deformation, volcanism, or dynamic topography. The associated transient changes in land-sea distributions influence the migration, genetic drift, adaptation, speciation, and endemism of the terrestrial biosphere that conquered emerged landmasses. Today, archipelagos located along subduction zones hostone-third of the biodiversity hotspots in the world (Myers et al., 2000). In this context, SUBUTTEC research team aim at combining geological and biological data to unravel the links between the subduction dynamics and terrestrial life in subduction zones based on the case study of the Antilles hotspot. This short and dynamic subduction zone, bounding the east of the Caribbean plate, is ideally circumscribed by two giant continents and two equally giant oceans that provide rather static boundary conditions. To unravel the role of the southern Lesser Antilles in the dynamics of Caribbean biodiversity, we will perform paleogeographic reconstructions over the last 20 Myrs, focused on the unknown role of the southern Lesser Antilles, will be done by integrating tectonics, paleomagnetism, (bio-)stratigraphy and geochronology. We will match these paleogeographic reconstructions with the assemblage distribution and phylogenetic records of extant endemic species, which will allow us to test for alternative scenarios of the temporal dispersion and evolution of life in this highly dynamic hotspot region for both biodiversity and tectonic activity. The implementation of comparative biogeographical methods provides here a powerful tool to reveal natural classification of biogeographic areas i.e. bioregionalization and identification of vicariant events. The joint analysis of the geological and biological records will provide a macro-ecological framework of the biosphere/biodiversity dynamics over subduction zones.

How to cite: Philippon, M., Roncal, J., Cornée, J. J., Quillevere, F., Arcay, D., Cerpa, N., Husson, L., Boucharat, Y., Rousteau, A., Ung, V., Bezault, E., Lorcery, M., Bernet, M., Sarr, A.-C., Riel, N., Kaus, B., Pubellier, M., Thivaiou, D., Montheil, L., and Noury, M. and the SUBUTTEC Team: SUBUTTEC Project: SUBdUcTion triggered Terrestrial Evolution in the Caribbean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20984, https://doi.org/10.5194/egusphere-egu25-20984, 2025.

The Guaymas Basin is a large marginal rift basin in the Gulf of California with ongoing seafloor spreading and strong hydrothermalism centered around two axial troughs. Extremely high concentrations of methane are discharged from diffuse hydrothermal flow, black smokers, and cold seeps. A thick sediment layer across the basin allows for thermocatalytic production of methane in the hot subsurface, resulting in the discharge of hydrothermal fluids from powerful black smokers with temperatures exceeding 300°C. The cooler surface sediments additionally support methanogenesis, providing a complex interplay between the biogenic and abiogenic systems. The dynamism of the Guaymas Basin means that the flux and distribution of hydrothermal vents in this region can change rapidly, impacting the wider oceanography of the region.

We present here results from a 2024 study of hydrothermalism in the Guaymas basin using a new optical sensor, developed at the Woods Hole Oceanographic Institution. SAGE – the Sensor for Aqueous Gases in the Environment – utilizes laser absorption spectroscopy through a hollow core optic fiber to quantify the partial pressure of dissolved methane extracted from the deep sea. This in situ sensor, deployed during a cruise on the R/V Atlantis allows continuous measurement of methane concentrations with high spatiotemporal resolution, with a sampling rate of 1Hz and a stable response time of 1-5 minutes. This new sensing technique facilitated analysis of the relationships between microbial communities and hydrothermalism and guided dives towards hydrothermal vents based on the real-time methane concentration. It also allowed the comprehensive in situ analysis of a rapidly evolving black smoker vent site in the northern axial trough, allowing the methane export to the water column to be characterized with high spatiotemporal resolution. The low detection limit of SAGE – down to ~10 ppm – allows the analysis of the broader impact of these dynamic methane-based systems into the wider oceanography of the region.

How to cite: Michel, A., Burkitt-Gray, M., Marquardt, S., Youngs, S., Remar, J., Joye, S., and Kapit, J.: Chemical mapping of methane in the Northern Guaymas Basin hydrothermal field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21421, https://doi.org/10.5194/egusphere-egu25-21421, 2025.

The continent-derived nature of the western Philippines (Palawan-Mindoro Microcontinental Block; PCB) contrasts with the island arc-dominated eastern Philippines (Philippine Mobile Belt; PMB). Petrological investigation on the P-T-D history of the metamorphosed rocks in between these two terranes and how they relate to the broader tectonic events are however lacking. In this study, we examined rock units related to the arc-continent collision events in two areas: the Romblon Island Group and the central Zamboanga Peninsula.

In central Philippines, the Romblon Metamorphic Complex (RMC) represents the PCB-derived materials. The RMC consists of metapelitic and metapsammitic paraschists in Tablas, Romblon, and Sibuyan with minor orthoschists and marbles. Using two-feldspar geothermometery, and Raman Spectrometry of Carbonaceous Material, the temperature variations revealed a low P/TStage 1 metamorphism of all RMC units with peak T and P values of about 450-540°C at <5 kbars. Based on tensional structures (e.g. boudins) and preserved metapelitic-metapsammitic interlayering, we attribute this Stage 1 to the PMB continental rifting and subsequent shallowing of the paleogeothermal gradient. The RMC paraschists which are adjacent to the Sibuyan Ophiolite  Complex (SOC) meanwhile register significantly higher T at the same low P conditions (= 570-630 °C). This suggests a second stage of higher T deformation and metamorphism directly linked with the juxtaposition of the continental RMC and the island arc SOC. This is consistent with the subsolidus shearing and metamorphism of the isotropic gabbro units of the SOC with preserved P-T conditions of about 500-800°C.

The southern extension of the PCB-PMB collision is even less understood although earlier works extend the arc-continent suture zone in Mindanao Island, southern Philippines. The purported boundary of the continent-derived Zamboanga Peninsula and the island arc Eastern Mindanao is the northwest-southeast trending Siayan-Sindangan Suture Zone. Our field mapping in central Zamboanga Peninsula however revealed a distinct northeast-southwest trending suture zone of an apparent arc-continent collision zone. Across this NE-SW suture zone, the lithologies progress from the paraschists of the Gutalac Metamorphic Complex (GMC) in the northeast to the amphibolites of the Dansalan Metamorphic Complex (DMC). Further southeast, the residual peridotites and pillow lavas with intercalated chert, deep marine turbidites and limestones of the Polanco Ophiolite Complex (POC) are exposed. Such progression hints at a NE-SW convergence of an ancient arc (POC) with its metamorphic sole (DMC) against the continent-derived GMC following the consumption of an ancient oceanic basin.

How to cite: Valera, G. T., Badillo, J. K., Tabilog, A. E. S., Balanial, N. M., Alcancia, M. L., and Payot, B. D.: Understanding the arc-continent collision zones in western Philippines: Novel insights from the Romblon Island Group and the Central Zamboanga Peninsula, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21462, https://doi.org/10.5194/egusphere-egu25-21462, 2025.

The eastern Liaoning-southern Jilin tectonic zone (also referred to as the Liao-Ji tectonic zone), a potential zone for rare-metal and REE mineralizations in China, hosts over 10 rare-metal and REE deposits and ore occurrences with varying scales and mineralization characteristics, which establish this zone as an ideal target for research on the metallogenic regularities of rare-metal and REE mineralizations.The study area resides in the northern part of the East Asian continental margin, lying on the overlapping part of the North China and the Western Pacific Plates, is located in the northeastern North China Plate, consisting of the North China Craton and the north margin orogen of the North China Plate. This area serves as a critical large-scale copper-gold and polymetallic mineral resource base in China, also providing favorable geologic conditions for the enrichment and mineralization of rare metals and REEs. So far, many rare-metal and REE deposits and ore occurrences have been discovered in the Liao-Ji tectonic zone, including two large Nb-Be-Zr-REE deposits (i.e., Lijiapuzi and Pianshishan), two medium-sized Rb-Be-Nb-Ta-REE deposits (i.e., Saima and Gangshan), one small Nb-Ta-REE deposit (i.e., Shijia), and over 10 rare metal-REE ore occurrences (e.g., Xiaolizi, and Baiqi), suggesting considerable mineralization potential. Most of the deposits in the Liao-Ji tectonic zone are closely associated with alkaline rocks.

Extensive field surveys and geochemical studies of the above deposits reveal that the ore-forming rock masses of the Pianshishan, Gangshan, and Lijiapuzi deposits include alkaline granites and pegmatites and those of the Shijia and Saima deposits are quartz syenites and aegirine nepheline syenites, respectively. The Pianshishan (67±2.2 Ma) and Gangshan (110±1.2 Ma) deposits were formed during the Yanshanian, the Shijia (226.3±2.4 Ma) and Saima (224.4±6.1 Ma) deposits originated from the Late Indosinian magmatism, while the formation of the Lijiapuzi deposit (2501±11 Ma) was associated with the Lvliang Movement. Therefore, the study area underwent three stages of regional rare-metal and REE mineralizations: the Late Yanshanian (Mesozoic), Late Indosinian (Mesozoic), and Proterozoic Lvliangian mineralizations. The petrogeochemical analysis indicates that the ore-forming rock masses of several typical deposits all belong to the metaluminous, alkaline - calc-alkaline, and tholeiitic basalt series, sharing similarities with the elemental geochemical characteristics of intraplate rift rock series and rocks in an extensional environment under plate subduction. The rare-metal and REE mineralizations in the study area were primarily governed by the evolution and crystallization differentiation of alkaline magmas. Given that the alkaline magmatic rocks were all formed by crust-mantle contamination, this study posits that the enrichment and mineralization processes of rare metals and REEs in the Liao-Ji tectonic zone are intimately associated with the highly evolved alkaline magmas. Under the action of water and volatile constituents, magmas underwent intense fractional crystallization, leading to the migration and accumulation of ore-forming elements. With changes in ore-forming conditions such as temperature and pressure, ore-bearing fluids became enriched and mineralized in the late stage of magmatism with the crystallization of primary rock-forming minerals.

How to cite: Ju, N., Yang, G., Zhang, P., Li, J., Wu, Y., Lu, S., Liu, B., Yang, X., Liu, X., and Feng, Y.: Rare-metal and rare earth element mineralizations in the eastern Liaoning-southern Jilin tectonic zone in Northeast China: A review, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2404, https://doi.org/10.5194/egusphere-egu25-2404, 2025.

The second member of the Fengcheng Formation in the early Permian of the Mahu Depression has a rock series with interbedded alkali mineral layers and tuffaceous layers. The dark layer contains a large amount of associated metal minerals, which are closely related to the volcanic hydrothermal material at the Fengnan fault nose. However, due to the presence of detrital rock deposits on the west side of the Mahu Depression, this area is jointly controlled by volcanoes and terrestrial sources to form alkali mineralization. There are also a large number of dark hydrocarbon source rocks developed in the region, which are also one of the reasons for the mineralization of alkali minerals and associated metal minerals. Therefore, a mineralization model is established.

How to cite: Liu, X. Y., Longwei, Q., and Yongqiang, Y.: Enrichment Factors of Alkali and Key Metal Mineral Resources in Fengcheng Formation of Mahu Sag, the Junggar Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2960, https://doi.org/10.5194/egusphere-egu25-2960, 2025.

The Global Navigation Satellite Systems - Interferometric Reflectometry (GNSS-IR) method has been utilized for nearly fifteen years as an alternative and cost-effective approach to determine hydrological parameters such as sea level, snow depth, and soil moisture through the analysis of signal-to-noise ratio (SNR) data. Most GNSS-IR studies to date rely on archived data and post-processed results. However, the potential for near real-time GNSS-IR analysis is increasingly being explored. In this study, high-rate GNSS archive data, sampled at 1-second intervals and stored in 15-minute files, were processed in a simulated near real-time workflow. Every 15 minutes, new data were added to the analysis, focusing exclusively on the most recent 60 minutes of observations. A novel approach for detecting outliers in near real-time GNSS-IR estimates was also proposed. The median-based robust outlier detection (ROD) method, previously validated for post-processed GNSS-IR snow depth results, was adapted and applied to near real-time GNSS-IR data. A 30-day dataset of multi-GNSS, multi-frequency SNR observations from the Portland (PTLD) GNSS station in Australia, collected in November 2024, was analyzed. The near real-time GNSS-IR results were validated using sea level measurements from the PORL tide gauge station. The results demonstrate that the modified ROD approach can be used to identify outliers in near real-time GNSS-IR sea level retrievals.

How to cite: Altuntas, C., Erdogan, B., Tunalioglu, N., and Williams, S.: Improving near real-time GNSS-IR sea level retrievals with robust outlier detection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3157, https://doi.org/10.5194/egusphere-egu25-3157, 2025.

The bauxitic region of Sumbi and its surroundings in Kongo Central (DR Congo) is located in an area corresponding to “bands” of basic rocks made up of microdolerites, basalts and andesites. The problem of this study is linked to the similarity of the phenomena that generated the depositional process of these ferruginous and aluminous formations. The aim of this article is to carry out a chemical and petrographic study of samples of bauxitic materials from the Mayedo and Kinzoki regions, with a view to their possible recovery. To this end, the chemical and petrographic analysis of the weathering formations outcropping in the study area was carried out using X-ray fluorescence and thin section methods. The latter revealed that two lithologies were detected in the healthy rocks: basalts with a mineralogical assemblage of plagioclase crystals, pyroxene microcrystals and oxide opaques; and dolerites represented by plagioclase crystals, pyroxenes and a few quartz crystals. X-ray fluorescence revealed high levels of Al₂O₃ (32.69%) in the Mayedo zone (MHb1). This visibly gibbsite-rich level corresponds to the zone of friable, homogeneous bauxite with a massive, blood-red texture, with an estimated gibbsite percentage of 55.50. The percentage of Fe₂O₃ is high in these zones at 42.77%, hence the dark red colour, reflecting a strong zone of ferruginasation. This horizon contains a high concentration of hematite and goethite minerals. Highly variable SiO₂ contents ranging from 13.48% to 40.82%. These variations are essentially due to the dissolution of silica by leaching and resilification.

How to cite: Mwanakangu, E. and Ungu, D.: Petrographic and Geochemical Characterization of Mayedo and Kinzoki Ranges (Sumbi Bauxite Region, Kongo Central/DR Congo), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3874, https://doi.org/10.5194/egusphere-egu25-3874, 2025.

High-precision GNSS coordinate time series modeling and prediction provide a critical reference for applications such as crustal deformation, structural safety monitoring, and regional or global reference frame maintenance. A Deep neural network framework based on Transformer was applied to 22 GNSS stations, each with 1000 days, in which data is preprocessed using a synchronization sliding window. The overall fitting and prediction trends exhibit a high degree of consistency with the original time series. The average fitting RMSE and MAE are 3.40 mm and 2.64 mm, respectively, while the corresponding average prediction RMSE and MAE are 3.54 mm and 2.77 mm. In comparison to the LSTM model, the proposed method achieved a redu78ction in RMSE and MAE by 20.7% and 19.6%, respectively. Furthermore, when benchmarked against the traditional least squares approach, the improvements were even more pronounced, with RMSE and MAE decreasing by 35.7% and 37.8%, respectively. The approach demonstrates robustness and effectiveness under conditions of discontinuous data. Therefore, it could be used as a convenient alternative to predict GNSS coordinate time series and will be of wide practical value in the fields of reference frame maintenance and deformation early warning.

How to cite: Wang, J., Li, Z., and Jiang, W.: Deep Neural Networks for GNSS Coordinate Time Series Modeling and Prediction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4633, https://doi.org/10.5194/egusphere-egu25-4633, 2025.

The Vemula-Velpula hydrothermal barite deposit is hosted by mafic dykes (ca. 1850 Ma. [1]) intruding into the uppermost part of about 1900 m thick carbonate strata of the Vempalle Formation (ca. 2000 Ma. [2]) in Cuddapah basin and occurs as fracture-fill and breccia-fill veins. The veins dominantly consist of barite with minor quartz. The host mafic rock has undergone various extents of hydrothermal alteration, due to which the primary calcic plagioclase-clinopyroxene assemblage is altered to albite and clinochlore, along with the introduction of secondary epidote, quartz, and calcite. The wide range in Ba concentration of mafic rock (68 to 3012 ppm) associated with the barite mineralization indicates that Ba was mobilized and subsequently leached from the mafic rock by the hydrothermal fluid during this alteration event. The δ³⁴S values of barite range from +16.19 to +23.24‰ which falls within the range of δ³⁴S value of +10 to +30‰ estimated for Proterozoic seawater [3]. At shallow crustal depth where this deposit was formed, direct participation of seawater is unlikely and therefore basinal brine is inferred to be the source of sulphate ion required for barite mineralization. Primary aqueous biphase fluid inclusions in barite have homogenization temperatures ranging from 180 to 300 °C, with most of them clustering in the range 220-250°C, and salinities ranging from 2.4 to 25.8 wt.% NaCl equivalent. The first ice melting temperature of these inclusions was measured between -55 and -37°C, broadly pointing towards an H₂O-NaCl-CaCl₂ fluid system. Petrography and microthermometric data of fluid inclusions indicate the involvement of two fluids of different salinities, which, upon mixing and cooling, led to barite precipitation.

This research work was funded by SERB, New Delhi (Scheme No. CRG/2019/001015).

References

[1] Chakraborty K. et al. (2016), Journal of the Geological Society of India 87, 631–660.

[2] Rai A.K. et al., (2015), Journal of the Geological Society of India 86, 131–136.

[3] Strauss H (1993) Precambrian Research 63(3–4), 225–246.

How to cite: Devanand Sreekala, D. and Muthusamy, S. P.: Insight into the genesis of barite deposit in Vempalle Formation, Cuddapah basin, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4666, https://doi.org/10.5194/egusphere-egu25-4666, 2025.

Direct ore-mineral U-Pb geochronology of scheelite (CaWO₄), cassiterite (SnO₂), and wolframite ([Fe,Mn]WO₄) using recently-developed reference materials led to new ore-genesis insights for multiple worldwide W-Sn/rare metal deposits. Scheelite from the Yellow Pine epithermal Au-W-Sb deposit in Idaho, USA was age dated using U-Pb via isotope dilution thermal ionization mass spectrometry (TIMS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). These analyses provided both the first age constraints on the tungsten mineralization (ca. 57 Ma) and a scheelite U-Pb reference material (NMNH-107667; 57.52 ± 0.22 Ma). The data reveal ore mineralization occurred in numerous discrete pulses during crustal uplift, which contrasts with the previous two-mineralization-event model.

The Yellow Pine scheelite reference material enabled U-Pb scheelite geochronology via LA-ICP-MS for multiple other deposits worldwide; namely, the polyphase stratabound scheelite-ferberite mineralization hosted within Fe-rich magnesite zones and marbles in two locations around Mount Mallnock, Austria. Two unexpected but geologically meaningful age dates (294 ± 8 Ma) for Mallnock West and (239 ± 3 Ma) for Mallnock North revealed for the first time that ore mineralization occurred during an extensional geodynamic setting as part of the breakup of Pangea, as opposed to the previous model invoking the older compressional tectonics of the Variscan orogeny.

Combining direct-ore geochronology methods for several ore minerals was particularly powerful for Sn- and W-bearing deposits in southeast Australia. A U-Pb cassiterite age date (435 ± 2 Ma) revealed the tin-bearing lithium pegmatites of the Dorchap Dyke Swarm are ca. 15 Ma older than some previous estimates suggesting mineralization was related to the earliest magmatic activity recorded in the Wagga-Omeo Metamorphic Belt. Additionally, a new U-Pb wolframite age date (395 ± 5 Ma) for the Womobi polymetallic (W-Mo-Bi) deposit is ca. 21 million years younger than the host Thologolong granite, suggesting the granite was a passive host that was mineralized by a concealed intrusion. Both instances revealed mineralization ages that were significantly different than previously accepted. More widespread application of these increasingly diverse, direct-ore geochronology methods stand to replace uncertain spatial or textural associations, thereby providing an opportunity to significantly improve ore genesis models.

How to cite: Wintzer, N., Holm-Denoma, C., Altenberger, F., and Waugh, S.: W-Sn Ore-Mineral Geochronology: New Ages Improve Genesis Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5245, https://doi.org/10.5194/egusphere-egu25-5245, 2025.

The relationship between the length of day (LOD) and the El Niño-Southern Oscillation (ENSO) has been extensively studied since the 1980s. LOD represents the negative time derivative of UT1-UTC, directly proportional to the Earth Rotation Angle (ERA), a key Earth Orientation Parameter (EOP).

ENSO is a climate phenomenon occurring in the tropical eastern Pacific Ocean that primarily impacts the tropics and subtropics. Extreme ENSO events can lead to severe weather conditions, such as flooding and droughts, across various regions worldwide. ENSO event undergoes a lengthy incubation period, during which the interannual variations in length-of-day (LOD) and atmospheric angular momentum (AAM) are rapidly influenced by the interactions between the ocean and the atmosphere.

The significant characteristics of climate change are the rise of global temperature and sea level, which are driven by ENSO. Interannual oscillations in global mean sea temperature (GMST) and global mean sea level (GMSL) might also impact changes in the Earth’s rotation velocity.

The goal of this study is to explain in more detail connections among the interannual (2-8 years) variations of the LOD, AAM, and different climate indices, like the Southern Oscillation Index SOI, Oceanic Niño Index ONI, GMSL, and GMST. The influence of climate signatures on LOD from January 1976 to December 2024 is assessed using semblance analysis based on continuous wavelet transform. This method evaluates the correlation between climate time series in the time and wavelength domains.

Studying the relationship between LOD, AAM, GMSL, GMST, and ENSO indices enhances our understanding of Earth's dynamic system, improves geophysical models, and increases the precision of applications dependent on accurate timekeeping and Earth rotation measurements.

How to cite: Wińska, M., Śliwińska-Bronowicz, J., Nastula, J., and Staniszewska, D.: Length of the Day changes and climate signatures- their relations in detected ENSO Events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8007, https://doi.org/10.5194/egusphere-egu25-8007, 2025.

Anelasticity is a type of rheology intermediate between elasticity and viscosity, responsible for rock’s transient creep behaviour. Whether to consider anelasticity in geodynamic processes operating outside the seismic frequency band which likely involve transient mantle creep is still under debate. Here, we focus on the geodynamic process of ocean tide loading (OTL), namely the deformational response of the solid Earth to the periodic ocean water-mass redistributions caused by astronomical tides. By analysing high-precision Global Positioning System (GPS) data from over 250 sites in western Europe and numerical OTL values from advanced three-dimensional Earth models, we unambiguously demonstrate anelastic OTL displacements in both the horizontal and vertical directions. This finding establishes the need to consider anelasticity in geodynamic processes operating at sub-seismic timescales such as OTL, post-seismic movement, and glacial isostatic adjustment (GIA) due to rapid ice melting. Consequently, to construct a uniform viscoelastic law for modelling Earth deformations across multiple timescales anelasticity must be incorporated. Our best-fitting anelastic models reveal the shear modulus in Earth’s upper mantle to be weaker at semi-diurnal tidal frequencies by up to 20% compared to the Preliminary Reference Earth Model (PREM) specified at 1 Hz, and constrain the time dependence of this weakening.

How to cite: Huang, P., Penna, N. T., Clarke, P. J., Klemann, V., Martinec, Z., and Tanaka, Y.: Signature of mantle anelasticity detected by GPS ocean tide loading observations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9320, https://doi.org/10.5194/egusphere-egu25-9320, 2025.

This study investigates the present-day seismotectonic framework of the High Atlas Mountains, Morocco, with a specific focus on the area affected by the devastating Mw 6.8 Al Haouz earthquake of September 8, 2023. Leveraging a high-resolution seismic dataset encompassing over twenty moderate earthquakes (M 3.5-6.8) recorded by regional networks between 2008 and 2024, the research aims to refine earthquake locations and characterize the regional stress field. Initially located using P-wave arrival times, earthquake hypocenters were subsequently relocated using the double-difference method, which yielded more precise locations by minimizing travel-time residuals between pairs of events recorded at common stations. The high degree of agreement between the initial and relocated solutions validates the robustness of the location estimates. Notably, the observed seismicity is confined to shallow crustal depths, consistently shallower than 30 km, corroborating the shallow rupture observed for the Al Haouz earthquake, which occurred at a depth of approximately 31 km. This shallow seismicity suggests a shallow deformation style within the High Atlas.

To determine the state of the present-day tectonic and stress regimes across the western and central segments of the High Atlas, the study uses two complementary approaches: regional seismic moment tensor inversion and P-wave first motion focal mechanism analysis. Fault plane solutions were calculated using P-wave first motion polarities and further constrained through regional moment tensor inversion. The majority of analyzed earthquakes exhibit reverse faulting mechanisms, often with a significant strike-slip component, indicating a complex deformation pattern. Analysis of the principal stress axes (P, B, and T) derived from the focal mechanisms reveals average orientations of 16/189, 39/036, and 08/104 (plunge/azimuth), respectively. Subsequently, tectonic stress tensor properties were derived through inversion of the focal mechanism parameters. The results of this stress inversion indicate a predominantly N-S oriented maximum horizontal stress (σ1) in the Western High Atlas, closely aligned with the faulting style of the Al Haouz earthquake. In contrast, the stress field in the Central High Atlas exhibits a transition to a NW-SE to NNW-NNE orientation of σ1. These spatially varying stress orientations are consistent with independently derived GPS velocities and available neotectonics data, which document ongoing shortening across the High Atlas. This integrated analysis provides a comprehensive understanding of the active tectonic deformation within the High Atlas, shedding light on the complex interplay of faulting styles and stress orientations, and providing crucial insights into the source mechanism and broader tectonic context of the Al Haouz earthquake within the Western High Atlas region.

How to cite: Oujane, B., El Moudnib, L., Zeckra, M., Badrane, S., and Nouayti, A.: Seismotectonics of the Intracontinental High Atlas Mountains, Morocco, Derived from Regional Seismic Moment Tensor Analysis: Insights into tectonics and stress regimes., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9503, https://doi.org/10.5194/egusphere-egu25-9503, 2025.

North East India (NEI) is situated between the Himalayan collision arc to the north and the Indo-Burmese Ranges (IBR) to the east. The tectonic unit of the NEI, Shillong Plateau (SP), is one of the most active seismotectonic zones of the Indian subcontinent, as demonstrated by its seismicity. It is crucial to identify active faults in populated areas for human safety and the sustainable development of society. The gravity method is one of the convenient methods to delineate the shallow to deeper subsurface discontinuities, i.e., it is useful to detect active faults in the subsurface compared to other geophysical methods (e.g., Electrical, and Electromagnetic methods). In this study, detailed multilayer horizontal tectonics stress (HTS) was calculated using the approach of multi-scale decomposition of gravity anomalies data. HTS can be helpful in demarcating shallow to deep-seated tectonic structures. The tectonic features exhibit a strong correlation with the distribution of HTS at different depths. Major faults and earthquake epicentre align with areas of high stress, while stable zones correspond to regions of low stress. It means that HTS is employed to deduce the distribution and stability of faults. The high value of HTS is increased from shallow to deep depths for SP, Mikir Hills, IBR and Eastern Himalaya in the NEI region, and it varies as ~ 0.2-0.53 MPa, ~ 0.24-0.61 MPa, ~ 0.3-0.84 MPa, ~ 0.4-1.2 MPa, ~ 0.57 1.86 MPa, ~ 0.8-2.4 MPa, ~ 0.84-3.0 MPa at 4, 8, 12, 20, 40, 50, and 60 km depths, respectively. While the Brahmaputra Valley and the Surma Basin show relatively less stress, where HTS varies between ~ 0.1-0.33 MPa for 4, 8, 12, 20, 40, 50, and 60 km depths. It can be interpreted that the populated SP and Mikir Hills are highly unstable or earthquake-prone regions due to high stress.

How to cite: Pathak, P. and Kumar Mohanty, W.: Horizontal tectonic stresses and its implications in the Shillong Plateau and its adjoining using gravity data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9618, https://doi.org/10.5194/egusphere-egu25-9618, 2025.

The Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC) aimed to evaluate and compare various methods of Earth Orientation Parameters (EOP) predictions. One of the goals of the 2nd EOP PCC was to prepare a combination of the predictions to obtain one robust and accurate solution for forecasts of individual parameters. This presentation focuses on identifying the most reliable and accurate combination of predictions for polar motion (PMx, PMy), universal time variations (UT1-UTC), and length of day (LOD) among the methods tested during the 2nd EOP PCC.

Two types of experiments were designed for this study: "operational" combinations tailored to real-time comparisons and practical application and "final" combinations designed for comprehensive analysis. Boths approaches incorporated six methods for handling outlier predictions, ranging from no filtration to progressively stricter criteria using the σ+β method (with α values ranging from 5 to 1). All experiments cover the period of 2nd EOP PCC (from September 1, 2021, to December 31, 2022), and each approach includes 70 10-day predictions.

The results show that combining various submissions generally enhances stability and accuracy of EOP forecasts. The σ+β criterion with α = 1 achieved the smallest Mean Absolute Prediction Error, indicating high accuracy of prediction. However, this method of eliminating outliers forecasts is the most restrictive, as it excludes a significant number of predictions. In contrast, operational combinations without filtering proved more practical for real-time applications, albeit with slightly higher errors.

The findings underscore the importance of tailoring combination strategies to specific goals—whether prioritizing maximum accuracy or practical applicability. This research highlights the benefits of prediction combination methods in improving EOP forecasts, offering a foundation for further development of operational strategies and expanding their use in geophysical and astronomical applications.

How to cite: Michalczak, M., Śliwińska-Bronowicz, J., Wińska, M., Partyka, A., Ligas, M., and Nastula, J.: Exploring various approaches to combine Earth Orientation Parameter (EOP) predictions gathered during the Second EOP Prediction Comparison Campaign (2nd EOP PCC), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9658, https://doi.org/10.5194/egusphere-egu25-9658, 2025.

This study introduces a methodology designed to enhance the accuracy of Celestial Pole Offset (dX, dY) prediction, with a focus on a short-term forecast horizon (up to 30-days). IERS EOP final data as well as those published by JPL are used as input for the  prediction algorithms. The prediction procedure is consistent, in the sense that, it does not rely on any external data to fill any latency gaps in the final IERS product. This is handled within the prediction routine itself by enlarging the forecast horizon to the gap filling horizon and proper forecast horizon. In this way, the presented methodology is ready to use under operational settings what makes it well suited for real time applications. Such an approach enables also to asses prediction capabilities of the methods in offline experiments whilst maintaining the operational settings. JPL CPO data serves as supplementary series for prediction and adjusting using Deming regression to align it  with IERS CPO values (attempt to assess fixed and proportional biases between series). The prediction strategy applies also the Whittaker-Henderson smoother to IERS CPO series, which after smoothing is treated as an additional source of information in the prediction process. Separate predictions based on JPL, IERS and smoothed IERS series are also averaged in different combinations giving rise to ensemble data-based prediction model. In this way we show that the overpredictive and underpredictive characteristics of specific input data, even with the application of a single prediction method, can result in a more precise and accurate final forecast. The presented approach was tested against the results obtained within the course of the 2^nd EOPPCC, as well as other contemporary studies. This presentation includes also a comparison of performance of the method in reference to different series, i.e., IERS EOP 14 C04 and IERS EOP 20 C04.

How to cite: Ligas, M., Michalczak, M., Belda, S., Ferrándiz, J. M., Karbon, M., and Modiri, S.: Enhanced Celestial Pole Offset forecast via combination of different data sources, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11708, https://doi.org/10.5194/egusphere-egu25-11708, 2025.

Geodetic VLBI (Very Long Baseline Interferometry) currently consists of two observing networks (legacy S/X and broadband VGOS). Heretofore, the two networks have run rather independently, which is non-ideal. There have been several attempts to combine observations from both networks at sites with co-located antennas using either conventional local-tie surveys or VLBI tie-sessions between S/X and VGOS, or both. Unfortunately, the number of sites with co-located VLBI antennas is rather limited, which hampers progress. To overcome this problem, we proposed an approach, the so-called mixed-mode VLBI tie session, that does not require to have co-located VLBI antennas. Instead, mixed-mode sessions have the S/X and VGOS networks observed simultaneously as a single geodetic VLBI technique to thus obtain global ties between the two networks. Two of the sessions observed in 2020 were already included in the ITRF2020 combination. We hypothesize that the global-tie approach helps preserve the geometry of the networks when aligning with the state-of-art ITRF2020 frame. In this presentation, we will describe the observed mixed-mode sessions, detailing scheduling strategies, correlation techniques, and geodetic processing methods used. We will also demonstrate how mixed-mode sessions can help realize a stable global geodetic reference frame such as the ITRF.

How to cite: Mondal, D. R., Elosegui, P., Ruszczyk, C., Lemoine, F., and Behrend, D.: Global VLBI ties using mixed-mode sessions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12533, https://doi.org/10.5194/egusphere-egu25-12533, 2025.

The progressive development of navigation technology has significantly improved real-time positioning accuracy, addressing the needs of modern applications. GNSS (Global Navigation Satellite System) is the primary system used for precise positioning across various platforms. However, GNSS is susceptible to errors, particularly interference, which degrades signal quality and compromises accuracy. Auxiliary systems such as INS, gyroscopes, and map-matching algorithms enhance reliability during interference but depend on GNSS for initialization. Signal detection algorithms, often employing CRPA (Controlled Reception Pattern Antennas) and advanced computational techniques, are essential for mitigating the impact of interferences and ensuring reliable navigation. This study compares the performance of two CRPA systems with different GNSS modules and algorithms, subjected to spoofing-jamming interference during experiments. The first CRPA, integrated with the u-blox ZED-F9P module, supports GPS, BeiDou, and Galileo satellites, employing an adaptive notch filter and pulse blanking. The second CRPA, featuring the Unicore UM980 module, supports GPS, BeiDou, and GLONASS satellites, utilizing a space-time algorithm alongside the JamShield adaptive mechanism for interference mitigation. In this study, real-time measurements were conducted on a car-mounted device platform under normal operating conditions. The platform was tested stationary for 5 minutes, followed by 15-minute intervals at speeds of 60 km/h. During each interval, 5 minutes of jamming and 5 minutes of spoofing were applied, with independent spoofing signals introduced. Jamming signals reached up to 50 dB-Hz, and spoofing signals were applied at levels up to 32 dB-Hz using a specialized interference device. During constant-speed travel, the second CRPA tracked 28 satellites with an HDOP of 0.5, while the first CRPA tracked 23 satellites with an HDOP of 0.75. Under jamming conditions, The second antenna maintained consistent satellite visibility, whereas the first experienced a pronounced decline in the number of observable satellites. Similarly, spoofing had no adverse effect on the second antenna, but the first suffered reduced satellite counts and positional accuracy. Additionally, the first antenna consistently underestimated the vehicle’s speed by approximately 5 km/h and exhibited a speed fluctuation of 0.5 m/s under interference conditions. 

How to cite: Karlitepe, F., Sezen, S., Velibasa, B. E., and Kabalci, A.: Advancements in Navigation Technology and Robustness Against GNSS Interference: A Comparative Analysis of CRPA , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12972, https://doi.org/10.5194/egusphere-egu25-12972, 2025.

The need to improve Earth rotation theories and models in a consistent and accurate
manner is currently widely recognized. Several researchers and groups at different
institutions have been working on this problem using quite different approaches, either
from the theoretical or computational perspective.
A potential source of the loss of accuracy of celestial pole offsets can be due to the
mismodeling of the planetary component of the IAU2000 nutation series. In fact, as
recognized in Ferrándiz et al. (2018), this component is actually based on a rigid-Earth
solution and does not include the Oppolzer terms that are significantly affected by the
Earth non-rigidity.
Such hypothesis was showed to be realistic by adjusting directly the amplitudes of a
small number of nutation periods of strictly planetary origin that could be reasonably
well separated by analyzing the series of VLBI observations. The results provide
significant fittings and the WRMS was successfully decreased by amounts comparable
to those achieved with lunisolar amplitude rescaling. A further step in this direction
requires the consideration of theoretical developments for the amplitudes of the non-
rigid Earth planetary nutations.
In this contribution, we present preliminary results considering the analytical formulae
of such planetary amplitudes for a two-layer earth model including dissipation effects at
the core-mantle boundary and anelasticity, obtained from a Hamiltonian method. Their
performance is assessed using several series of VLBI observations, with satisfactory
results, and is placed in the general context of the improvement of the precession and
nutation models sought by the IAG and the IAU.
Acknowledgment. This research was supported partially by Spanish Projects PID2020-119383GB-I00 funded by
Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033); SEJIGENT/2021/001, funded by
Generalitat Valenciana; and the European Union—NextGenerationEU (ZAMBRANO 21-04).

How to cite: Zerifi, A. Z., Ferrándiz, J. M., Escapa, A., Baenas, T., Juárez, M. A., Belda, S., and Karbon, M.: Performance of a new set of analytical corrections to planetary nutations: preliminary results and outlook, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13099, https://doi.org/10.5194/egusphere-egu25-13099, 2025.

The rapidly changing climate is amplifying both the frequency and severity of extreme weather events in the Azores archipelago, Portugal. Understanding the underlying dynamics of these events is essential for effective mitigation. Atmospheric water vapor data derived from the Global Navigation Satellite System (GNSS) data and reanalysis outputs from an atmospheric general circulation model offer valuable tools for studying the behavior of weather fronts around the Atlantic Ocean environment of the Azores. This research aims to conduct a detailed comparison between GNSS-based measurements and atmospheric reanalysis data, such as those available from ERA/MERRA2, focusing on the detection of small-scale atmospheric structures with high temporal resolution. We utilize atmospheric reanalysis products to decode long-term trends in the frequency and severity of extreme weather events in the Azores. We then apply statistical methods to identify consistencies and differences between these two approaches in capturing atmospheric water vapor patterns. By combining water-vapor estimates from both GNSS data and atmospheric reanalysis, we are able to characterize the dynamics of atmospheric turbulence from small (few meters) to large (few tens of kilometers) scales. 

How to cite: Ramrajvel, N., Mondal, D., Elosegui, P., Paine, S., Mateus, P., and Mendes, V.: Decoding the signal of extreme weather events in the Azores archipelago using GNSS and atmospheric reanalysis products, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13415, https://doi.org/10.5194/egusphere-egu25-13415, 2025.

Abstract.

The Isiro and Ngayu belts in northeastern Democratic Republic of Congo (DRC) are part of the Congo Craton and among the most poorly known Archean terrains worldwide. These belts consist of metavolcanic and metasedimentary rocks surrounded or intruded by granitoid rocks. minimum age of deposition for the supracrustal formations is defined at ca 2633 Ma (e.g. Allibone et al., 2020), whereas the granitoids were dated between 3200 Ma and 2530 Ma (Allibone et al., 2020; Turnbull et al., 2021) and are strongly deformed with variable proportions of mafic enclaves at outcrop scale (Turnbull et al., 2021). Both Isiros and Ngayu belts host important gold deposits, but the genetic relationships between gold mineralization, deformation and the diverse host rocks remain ambiguous. In this context, the work we present here is part of a multidisciplinary approach, combining the processing of satellite images and field observations using GIS to map the structural lineament that may control gold mineralization in the region. The results show that the strains are large, marked by NW-SE lineaments at low angle to the belt strikes and combined with a secondary ENE-WSW brittle structure. The overall structural pattern, together with the existence of artisanal gold mining in the area, emphasizes that gold mineralization is largely controlled by structures localization along the greenstone belts.

Key words: Congo craton, gold mineralization, field observations, satellites images, structural lineaments.

Reference

Allibone, A., Vargas, C., Mwandale, E., Kwibisa, J., Jongens, R., Quick, S., Komarnisky, N., Fanning, M., Bird, P., MacKenzie, D., Turnbull, R., Holliday, J., 2020. Chapter 9: Orogenic Gold Deposits of the Kibali District, Neoarchean Moto Belt, Northeastern Democratic Republic of Congo, in: Sillitoe, R.H., Goldfarb, R.J., Robert, F., Simmons, S.F. (Eds.), Geology of the World’s Major Gold Deposits and Provinces. Society of Economic Geologists, p. 0. https://doi.org/10.5382/SP.23.09

Turnbull, R.E., Allibone, A.H., Matheys, F., Fanning, C.M., Kasereka, E., Kabete, J., McNaughton, N.J., Mwandale, E., Holliday, J., 2021. Geology and geochronology of the Archean plutonic rocks in the northeast Democratic Republic of Congo. Precambrian Research 358, 106133. https://doi.org/10.1016/j.precamres.2021.106133

How to cite: Birimwiragi Namogo, D., Martial Akame, J., Mbuluyo, M., Debaille, V., Mango Itulamya, A. L., and Hubert-Ferrari, A.: Geology of the Isiro-Ngayu gold-bearing region, western belts of the Kibali granite-greenstone superterrane in the northeastern Congolese craton, Democratic Republic of Congo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13796, https://doi.org/10.5194/egusphere-egu25-13796, 2025.

The Crustal Dynamics Data Information System (CDDIS) provides essential support for the Global Geodetic Observing System (GGOS) by operating a data and product archive for the main geodetic techniques.   As GGOS matures and grows, the CDDIS adopts the latest data practices to strengthen its support for the community and ensure quality products are available in a timely manner.  This poster explores the breadth of work done at the CDDIS and provides highlights of the latest developments including new data and product holdings, updates to provide clarity and usability for users, and updates on future works. Statistics on usage will also be provided.

How to cite: Woo, J.: The Crustal Dynamics Data Information System (CDDIS) Updates for 2025, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13924, https://doi.org/10.5194/egusphere-egu25-13924, 2025.

Abstract

Urban surface dust and soils serve as a primary source and reservoir of metals that substantially impact human health and urban ecosystems. This study investigates the impact of metal contamination on urban surface soils from diverse land-use locations and their potential risk to human health in Jammu City, India. A total of fifteen surface soil samples were collected to evaluate the total metal concentration (As, Cu, Fe, Mn, Ni and Zn), Contamination Factor (CF), Geo-accumulation Index (Igeo), Pollution Load Index (PLI), and Potential Ecological Risk Index (PERI). The research findings of this study revealed significant variation in metal concentration. In comparison to Upper Continental Crust (UCC, taken as background here), the average concentration of Fe and Mn is lower across all locations, whereas As, Ni, Cu, and Zn are significantly higher over all locations. Elevated levels of Fe and Mn were observed higher near samples collected from industrial zones while Ni, As, Cu and Zn showed wider distribution throughout the study area. Apart from all metals, high As content was observed at near-construction and high-traffic interactions. Higher CF (CF > 6) and PLI values in surface soil samples revealed high contamination of As, Cu, Ni and Zn due to intensive industrial and vehicular emissions in the study area. Igeo values in surface soil samples indicated severe contamination of As, Cu, Ni and ZN in the study area, while Fe and Mn showed no contamination. PERI assessment in surface soil samples revealed extremely high ecological risk for As and Cu in Jammu City. Risk index values indicated that 40% of surface soil samples carried a very high risk (RI > 600) of metal contamination in the study area. The overall findings advised that industrial, transportation, and construction activities need to be improved to protect the region's environment and public health.

Keywords: Heavy metals, geo-accumulation index (IGeo), risk assessment, roadside dust.

How to cite: Gorka, R. and Kumar, R.: Spatial Distribution and Contamination Levels of Heavy Metals (Fe, Mn, Ni, Cu, As, and Zn) in Urban Topsoils of Jammu City, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14122, https://doi.org/10.5194/egusphere-egu25-14122, 2025.

Low Earth Orbit (LEO) satellites have the advantages of high flight velocity and minimal influence from external environmental factors on onboard observation. Integrating LEO satellite observations with ground observations can improve the accuracy and convergence performance of GPS and LEO real-time orbit determination, which can simultaneously meet the prerequisites for real-time Positioning, Navigation, and Timing (PNT) services for both GPS and LEO systems. Therefore, this study employs the Square Root Information Filter (SRIF) for GPS and LEO satellites real-time joint orbit determination (RTJOD). Based on observations from eight existing scientific LEO satellites, a detailed study on RTJOD was conducted under two scenarios: one using observations from 100 global stations and the other using observations from 9 regional stations in Australia. The results show that, with 100 global stations, incorporating LEO observations can significantly improve the convergence performance and GPS satellite orbit accuracy. The convergence times in the Along-track, Cross-track, and Radial components are reduced from 3.5, 5.8, and 10.3 h to 0.9, 1.0, and 10.3 h, respectively. The accuracy improves from 5.8, 3.6, and 2.8 to 4.0 cm, 2.5 cm, and 2.5 cm. Additionally, the ambiguity resolution (AR) performance is significantly enhanced. The time required to achieve a 90% narrow-lane ambiguity fixing rate is reduced from 4.9 to 0.7 h. After AR, the orbit accuracy further improves to 3.1 cm, 2.3 cm, and 2.4 cm. In the case of the 9 regional stations in Australia, after incorporating LEO, the orbit accuracy of the float solution after convergence is comparable to that of the 100 global stations without LEO, with accuracies of 6.0, 4.8, and 2.9 cm in the three components. It is important to note that, due to insufficient observations in this case, AR does not result in any further improvement in accuracy. In addition, LEO can achieve orbit determination accuracy better than 5 cm within a short time in both station distribution scenarios. This ensures that RTJOD enables LEO and GPS to generate high-precision real-time orbits simultaneously. Finally, the processing time for each epoch in all scenarios is less than 5 seconds, ensuring that the GPS and LEO RTJOD can provide timely orbit updates.

How to cite: Lai, W., Huang, G., Wang, L., She, H., Xie, S., Xie, W., and Wang, Q.: Real-time high-precision joint orbit determination of GPS and LEO using SRIF, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15238, https://doi.org/10.5194/egusphere-egu25-15238, 2025.

Zenith Total Delay (ZTD) is a crucial parameter for understanding the effects of atmospheric conditions on satellite signals, constituting a fundamental aspect of precision positioning and atmospheric modeling applications. Traditional methods for ZTD estimation, including GNSS observations, numerical weather prediction models, and interpolation techniques, encounter critical limitations such as generalization constraints, sparse data availability, insufficient spatial coverage, high computational costs, and limited adaptability to dynamic atmospheric changes. Deep learning techniques provide substantial benefits, including processing large and complex datasets, enabling dynamic modeling, and delivering rapid and accurate estimations.

This study integrates real-time GNSS observations with high-resolution atmospheric reanalysis data from the ERA5 dataset to develop deep learning-based methods for ZTD estimation. GNSS data were sourced from 17 IGS tropospheric stations strategically selected to represent diverse geographic and climatic conditions. These stations supplied ZTD values and their temporal variations at 5-minute intervals, spanning February 2023 to January 2024. ERA5 data, offering hourly atmospheric parameters, necessitated the alignment of GNSS temporal resolution with ERA5 for spatial modeling. The spatial distribution of GNSS data was optimized using interpolation techniques to enhance the quality of inputs for deep-learning models.

The findings highlight the potential of deep learning techniques to enhance ZTD estimation processes. Future research will focus on integrating additional datasets, such as InSAR, to achieve higher spatial resolution and improved accuracy. Moreover, advanced deep learning architectures, including attention mechanisms, will be investigated to refine estimation methods and broaden their applications in atmospheric and geospatial studies.

How to cite: Tekin Ünlütürk, N. and Bak, M.: Deep Learning Approaches for Zenith Total Delay Estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15605, https://doi.org/10.5194/egusphere-egu25-15605, 2025.

A Global Geodetic Observing System (GGOS) affiliate is an organization or entity that collaborates with the Global Geodetic Observing System (GGOS) to enhance the global geodetic infrastructure and support the objectives of GGOS in a region.
With this goal, a GGOS affiliate was created to enhance geodetic infrastructure and scientific collaboration across the Iberian Peninsula and the Atlantic region. It is called GGOS IberAtlantic. This project focuses on improving the accuracy and reliability of geospatial data through the co-location and integration of geodetic space techniques to support various scientific and practical applications, including global reference frame maintenance, climate change monitoring, natural hazard assessment, in the perspective of a sustainable development. GGOS IberAtlantic aims to establish a robust network of geodetic stations, facilitate high-accuracy data collection, and promote international cooperation among geodetic institutions, contributing to a better understanding of Earth's dynamic processes. It is also focused on supporting decision-making in the area and bringing geodesy closer to society, specially to young scientists.
The upcoming presentation will outline the steps taken to establish the GGOS IberAtlantic group, as well as its future directions and objectives.

Acknowledgment. This presentation was supported partially by Spanish Project PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033)

How to cite: Azcue, E. and Ferrándiz Leal, J. M. and the GGOS IberAtlantic Governing Board: GGOS IberAtlantic Affiliate: Bringing Geodesy Closer to Society across the Iberian Peninsula and the Atlantic region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17154, https://doi.org/10.5194/egusphere-egu25-17154, 2025.

The neutral atmosphere that extending from the surface of earth to about 80 km overhead is the electrically neutral part (within a certain frequency band which GNSS signals fall) of the atmosphere. There is no doubt that neutral atmosphere has a delaying effect on transmitted radio waves. Spilker (1996) noted that the more precise term of this delaying effect is neutral atmosphere delay, even though this delaying effect has been traditionally referred to as just troposphere delay. At all events, the delaying effect has propagated into satellite observations, and we must deal with it appropriately in order to achieve precise satellite positioning results. There are many geodesists have been making their contributions to treatment of neutral atmosphere delay, and how to get satisfactory supports from numerical weather model data set is one of the efforts making to calibrate this delaying effect more precisely up-to-date. Currently, both Earth observation network and technology have great improvement, which results in wonderful increase of Earth observational data as well as the subsequent numerical weather model data set. Briefly speaking, numerical weather model data set which generally provided by different organizations and/or institutions is a global and/or regional gridded meteorological data set with specific temporal-spatial resolution. Generally, reanalysis data set and forecast data set are usually considered to be the two main data set representations, and they both provide two types of data level, i.e., three-dimensional pressure levels and two-dimensional surface level. The data set contains some usually used meteorological parameters, such as height, temperature, pressure, humidity. With these meteorological parameters, some main terms related to neutral atmosphere delay, such as hydrostatic/wet delay, gradient factors and mapping factors can all be calculated without any difficulty by using computing techniques like raytracing and interpolation. Undoubtedly, the performance of different types of data set that mentioned above in representing neutral atmosphere delay are not all the same. Definitely, some interesting and meaningful comparison results have found and widely propagated by many scholars. In this work, we put more emphasis on evaluation of the forecast data set from neutral atmosphere delay point of view, considering there is an objective fact that satellite positioning industry especially the (near) real-time positioning has vigorous development, in which the calibration of neutral atmosphere delay is required more and more accurate and timely-supported. Besides time-delayed reanalysis data set and time-advanced forecast data set, microwave radiometer data set and radiosonde data set are also employed. The first results show that empirical model such as UNB3 can only state the normal level of delaying effect and the obtained delay values are either larger or smaller; the pressure levels data set performs better than the surface level data set with very high proportion in time domain; even though reanalysis data set generally has good performance, forecast data set can work for the neutral atmosphere delay calibration with relatively satisfactory support in term of accuracy.

This work is supported by the National Natural Science Foundation of China (42304010), the Youth Foundation of Changzhou Institute of Technology (E3-6207-21-060, 31020222007).

How to cite: Wang, M.: First results about evaluation of forecasted numerical weather model data set in view of neutral atmosphere delay, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17506, https://doi.org/10.5194/egusphere-egu25-17506, 2025.

Tropospheric refraction is one of the major error sources in satellite-based positioning. The delay of radio signals caused by the troposphere ranges from 2m at the zenith to 20m at low elevation angles, depending on pressure, temperature and humidity along the path of the signal transmission. If the delay is not properly modeled, positioning accuracy can degrade significantly. Empirical tropospheric models, with or without meteorological observations, are used to correct these delays but they are limited in accuracy and spatial resolution resulting in up to a few decimeters error in positioning solutions. The present availability of ground-based GNSS networks and the state of the art of GNSS processing techniques enable precise estimation of Zenith Tropospheric Delays (ZTD) with different latency ranging from real time to post-processing.
We present a method for computing ZTD residual fields interpolating, through Ordinary Kriging, the residuals between GNSS-derived and model-computed ZTD at continuously operating GNSS stations. GNSS ZTD estimates, obtained in real time and in PPP mode, are augmented by a multi-prediction model based on a Graph Neural Network model trained using one year of Near Real Time ZTD observations and a model using a polynomial plus harmonic interpolation. A combination strategy is defined to merge GNSS ZTD estimates at sites with the predicted values, where predicted ZTD values act as hole fillers for stations missing from the GNSS network at the current epoch. The residual ZTD field, obtained from PPP/prediction model and ZTD empirical model, is modelled as a random process and for each epoch a variogram is estimated and fitted to characterize the spatial correlation of the process. At a known user location, ZTD value is obtained as the sum of site interpolated ZTD residual and modeled-ZTD value. The algorithm is validated with respect to GNSS ZTD estimates provided by an external provider at a selection of sites not included in the network used to fed the computation. Details about validation and possible improvements will be provided.

How to cite: Basoni, A., Pacione, R., Bagaglini, L., and Lanotte, R.: Real-Time ZTD correction grid based on augmented GNSS network for navigation services, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18280, https://doi.org/10.5194/egusphere-egu25-18280, 2025.

The University of Luxembourg (UL), in collaboration with the United Kingdom Met Office, continues to advance the provision of global and regional near real-time (NRT) Zenith Total Delays (ZTDs) from GNSS ground networks to support operational meteorological products within the EUMETNET EIG GNSS Water Vapour Programme (E-GVAP). E-GVAP facilitates coordination and uptake of NRT GNSS-based atmospheric monitoring, which is indispensable for assimilation in Numerical Weather Prediction (NWP) models across Europe, including at the Met Office, where high-temporal-resolution data enhance mesoscale weather forecasting. This study highlights the collaborative efforts of the Met Office and UL in delivering accurate, timely meteorological data from GNSS. The partnership has resulted in the development and enhancement of NRT processing systems using the state-of-the-art Bernese GNSS software version 5.4 (BSW5.4), generating ZTD products at both UL and the Met Office at 1-hour intervals globally and regionally, and at sub-hourly intervals regionally. Over the past year, UL has focused on developing hourly NRT ZTD solutions for global and regional networks, and more recently extending them to sub-hourly intervals (down to 15 minutes) for regional coverage, thereby refining the temporal resolution for E-GVAP users. In particular, we are now prepared to provide NRT products in the form of a global hourly product (ULGH), a regional hourly product (ULRH), and a regional sub-hourly product (ULRS) to E-GVAP. As part of the system's development, we validate our latest global, regional, and sub-hourly ZTD solutions against established NRT outputs from E-GVAP and benchmark post-processed Double-Difference Network (DDN) products, while also verifying Integrated Water Vapour (IWV) estimates against ECMWF Reanalysis v5 (ERA5). Finally, we highlight how higher-frequency updates can positively influence NWP assimilation in rapidly evolving weather situations, detailing data flow and latency management that ensure reliable NRT ZTD delivery to E-GVAP participants and the Met Office. By extending temporal coverage from hourly to sub-hourly in regional networks and continuing our global solutions, we advance the utility of GNSS-based atmospheric sensing for short-term weather forecasting, providing consistent, high-quality NRT GNSS products for meteorological operations in Europe and beyond. 

How to cite: Hunegnaw, A., Teferle, F., and Jones, J.: Extending Global and Regional Near Real-Time GNSS ZTD Solutions Using BSW5.4 at the University of Luxembourg: Contributions to E-GVAP , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18910, https://doi.org/10.5194/egusphere-egu25-18910, 2025.

The Geophysics Section of the Royal Institute and Observatory of the Navy (ROA) is structured into three main services: Seismology, Geomagnetism, and Space Geodesy, in addition to an auxiliary Meteorology service and participation in maritime scientific campaigns. Since its foundation, the ROA has played a pioneering role in Spain, being a member of the Spanish Commission of Geodesy and Geophysics and collaborating with international institutions across all its fields of activity, such as ILRS, IGS, INTERMAGNET, and GEOFON, as well as organizations like NASA and ESA, among others.

The Geomagnetism Service, established in 1879, studies the Earth's magnetic field and its variations to conduct scientific research. After several relocations due to electromagnetic interference, the current geomagnetic observatory is located at Cortijo de Garrapilos (Cádiz) and has been a member of INTERMAGNET since 2006. The Seismology Service dates back to 1898, when one of the 12 seismographs of the first global seismic network, promoted by geologist John Milne, was installed at the ROA. The current infrastructure is distributed across Spain and North Africa, including a short-period network for regional seismicity in the Gulf of Cádiz and the Alboran Sea, long-period stations for global seismicity, and the international Western Mediterranean network, in which prestigious institutions such as UCM and GFZ participate. The ROA has been involved in space geodesy with artificial satellites since the early days of the space era, starting just one year after the launch of the first SPUTNIK (1958) with the Baker-Nunn camera. This technique was followed by laser ranging (SLR) in 1975, when a station capable of tracking collaborative satellites was installed. By 1980, the station was exclusively operated by ROA personnel. Since then, the station has undergone constant upgrades to maintain a high level of operability. Today, it contributes to national and international tracking networks such as ILRS-EUROLAS and EU SST-S3T. Additionally, the ROA adopted GPS in the 1980s for geodetic studies and currently manages a GNSS network comprising 17 permanent stations spanning the southern Iberian Peninsula and North Africa. Maritime campaigns include studies in the Spanish Exclusive Economic Zone (EEZ), with objectives such as hydrographic surveys and geophysical exploration for seabed characterization. Since 1987, the ROA has also participated in Antarctic campaigns.

The Geophysics Section of the ROA combines tradition and advanced technology to contribute to the understanding of the Earth and space, consolidating its position as a national and international benchmark in the study of geophysical and geodetic processes. Evidence of this includes recent or ongoing scientific work over the past years: four doctoral theses (three of them in progress), various articles in high-impact journals, participation in numerous scientific projects, and extensive contributions to conferences. In this way, the ROA, through the Geophysics Section, fosters collaboration in geodesy through its active participation in international networks, addressing global scientific and societal challenges with cutting-edge technology and a multidisciplinary approach.

How to cite: Rodriguez Collantes, D., Sánchez Piedra, M. Á., Cabieces Díaz, R., and Fiz Barreda, J.: Scientific Legacy and Current Contributions of the Royal Institute and Observatory of the Spanish Navy: Impact on Geophysics, Geodesy, and other Scientific and Social Fields., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19802, https://doi.org/10.5194/egusphere-egu25-19802, 2025.

The accuracy and reliability of Earth Orientation Parameters (EOP) are significantly influenced by the geometric configuration of the Very Long Baseline Interferometry (VLBI) network. This astronomical technique employs a global network of radio telescopes to collect data. The distribution of VLBI antennas affects the triangulation process used to determine the positions of celestial sources, which is integral to the calculation of EOP. An optimal geometry yields more accurate and reliable EOP results, which are essential for many scientific applications.

This study examines the impact of different VLBI networks on EOP estimation, using data collected during several Continuous VLBI Campaigns (CONT) and designing alternative networks by removing various antennas and/or baselines from the original configuration. The results of this analysis aim to contribute to the refinement of EOP and the achievement of the stringent GGOS accuracy targets (i.e., a frame with accuracy at epoch of 1 mm or better and a stability of 0.1 mm/y).

How to cite: del Nido Herranz, L. D., Belda, S., Karbon, M., Ferrándiz, J. M., and Azcue Infanzón, E.: Influence of VLBI Network Geometry on the Estimation of Earth Orientation Parameters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20077, https://doi.org/10.5194/egusphere-egu25-20077, 2025.

The Residual Terrain Modeling (RTM) technique is commonly used to recover short-wavelength gravity field signals. However, classical gravity forward modeling methods for RTM gravity field determination face challenges such as series divergence, inefficient computation, and errors induced by tree canopy in Digital Elevation Models (DEMs). In this study, deep learning methods are employed to enhance the quality of the computed RTM gravity field. Experiments are conducted at the Wudalianchi airborne gravity gradiometer test site, which provides a large volume of precise gravity measurements. The Random Forest method is used to estimate and correct tree canopy height errors in DEMs. A fully connected deep neural network (FC-DNN) is introduced to efficiently calculate the RTM gravity field. Additionally, to improve the network’s generalization capability, a novel terrain information fusion regularization method is applied to create an Improved FC-DNN with a refined loss function. The accuracy, computational efficiency, and generalization performance of the deep learning method are evaluated and compared in the Wudalianchi volcanic region. The results demonstrate a significant improvement in the accuracy of the RTM gravity field when based on tree canopy-corrected DEMs. The RTM gravity fields determined using both FC-DNN and Improved FC-DNN achieve mGal-level accuracy, with a remarkable 10,000-fold increase in computational efficiency compared to the classical Newtonian integration method. The Improved FC-DNN exhibits superior generalization, with accuracy enhancements ranging from 7% to 21% compared to the standard FC-DNN.

How to cite: Yang, M., Zhang, B., Wang, L., Feng, W., and Zhong, M.: Deep learning in RTM gravity field modeling: A case study over Wudalianchi area, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20320, https://doi.org/10.5194/egusphere-egu25-20320, 2025.

Thanks to existing algorithms for Legendre functions, it is fairly possible to perform spherical harmonic transforms up to degrees as high as a few tens of thousands. In fact, many algorithms are often accurate even well beyond this point. From the practical point of view, however, hardware-related challenges emerge when the truncation degree exceeds, say, 100,000. For instance, to conduct a degree-100,000 spherical harmonic transform, be it forward or backward, it is necessary to store in memory about 75 GBs of spherical harmonic coefficients and about 149 GBs of the signal to be analyzed/synthesized at the Gauss--Legendre grid (with Driscoll--Healy grids, the signal-related memory even doubles). Although systems with that amount of shared memory are not rare, the point becomes clear when further extending harmonic degree to, say, 150,000 (168 GB + 335 GB) or beyond. With such extensive transforms, one has to sooner or later move to systems with distributed memory.

This contribution discusses the implementation of spherical harmonic transforms on distributed-memory systems in CHarm, which is a C/Python library for high-degree spherical harmonic transforms. To this end, CHarm employs the Message Passing Interface (MPI), allowing to distribute both the coefficients and the signal among a number of independent shared-memory systems that can communicate together. These could be, for instance, nodes of high-performance computing clusters or a few ordinary PCs interconnected via some network protocol (e.g., SSH). Since the computation of a signal at any point requires all spherical harmonic coefficients and vice versa, the amount of data transferred is immense. We show how this challenge is tackled in CHarm. Furthermore, we discuss how CHarm combines the MPI parallelization (between shared-memory systems), the OpenMP parallelization (within shared-memory systems) and the SIMD parallelization (within a single CPU core), all at the same time. As a toy example, some spherical harmonic transforms up to degree 100,000 and beyond are shown.

In Physical Geodesy, high-degree spherical harmonic transforms are useful, for instance, to model planetary topographies. More specifically, spherical harmonic degree 100,000 offers 200-meter spatial resolution on the Earth's surface. Systems with distributed memory thus make it feasible for spherical harmonics to capture fine details of the Earth's and other planetary topographies. As another use case, it is known that topography truncated at some finite non-zero harmonic degree generates gravitational field possessing an infinite number of spherical harmonics. Therefore, to accurately describe the gravitation field of, say, a degree-10,800 Earth's topography, the truncation degree of the implied potential series should generally be extended from 10,800 to degree as high as possible, say, 108,000 or so.

CHarm is free software available from https://github.com/blazej-bucha/charm. The documentation with cookbook-style examples can be found at https://www.charmlib.org.

This study was funded by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under the project No. 09I03-03-V04-00273.

How to cite: Bucha, B.: Spherical harmonic transforms up to degree 100,000 and beyond using distributed-memory systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-67, https://doi.org/10.5194/egusphere-egu25-67, 2025.

The Gravity Recovery and Climate Experiment (GRACE) mission has revolutionized our understanding of Earth’s mass redistribution. However, enhancing the utility of GRACE products remains challenging due to inherent trade-offs between the temporal and spatial resolution, constrained by the mission design. High autocorrelation at the first lag in geoid coefficient time series is a key feature that enables the development of improved forecasting frameworks. Building on this temporal persistence of gravity coefficients, we propose a predictive framework to characterize the relationship between monthly and finer temporal scale-uncertainties of geoid coefficients. The proposed method enables reducing the finer temporal scale-uncertainties to levels comparable with known monthly uncertainties within the ranges of higher spectral degrees. With reduced uncertainties of finer temporal scales for higher spherical harmonic degrees, this predictive framework sets the groundwork for enhancing the analyses of rapid mass variations in the context of regional hydrology.

How to cite: Kankanige, D., Vishwakarma, B., Liu, Y., and Sharma, A.: A forecasting framework for enhancing gravity variations of finer temporal scales., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-280, https://doi.org/10.5194/egusphere-egu25-280, 2025.

Specific yield (S_y) is defined as the ratio of the volume of water that saturated rock or soil yields by gravity to the total volume of the rock or soil. S_y is often taken as a constant that when multiplied to groundwater level change provides water volume change, hence it is crucial in validating Gravity Recovery And Climate Experiment (GRACE)-derived groundwater changes, providing estimates of available groundwater resources, and in modelling groundwater aquifers. In this study, we used GRACE data and available quality-controlled in-situ well data to estimate S_y instead. Our hope was that it would match the available S_y, however we observed a time-varying S_y. Upon further investigation we found a negative correlation between water level and S_y. Hence the time-evolution of S_y was due to changes in the water level. We processed available well data and GRACE(-FO) in India, the United States, Europe, and Australia, spanning from January 2004 to December 2022. We also developed a general law/empirical relationship between S_y and groundwater level. All regional-specific empirical relationships exhibit a decrease in S_y as the average groundwater level depth drops, but the decay rate of S_y is notably faster in India (0.17 ± 0.04 m^-1) compared to the United States (0.03 ± 0.01 m^-1), Australia (0.06 ± 0.02 m^-1), and European countries (0.04 ± 0.03 m^-1). This empirical expression allows for the estimation of S_y based on readily available groundwater level data, thus supporting large-scale groundwater assessments and modelling efforts. At the global scale, a 50% decrease in S_y results in a groundwater level depletion of ~17 meters. However, in India, due to a faster decay rate, the same 50% reduction in S_y causes a groundwater level depletion of ~4 meters. This relationship can be utilized by hydrologists, water resource managers, and policymakers to predict S_y and assess changes in groundwater levels over time, aiding in more effective and sustainable water resource management.

How to cite: Kumar, K. S., Suryawanshi, M. R., Varadaganahalli Anandagowda, C., Shaw, B., Sukumaran, V., Kochar, A., and Vishwakarma, B. D.: GRACE satellites and in-situ well data reveals that specific yield declines with depleting groundwater levels, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-864, https://doi.org/10.5194/egusphere-egu25-864, 2025.

Taiwan’s terrain is predominantly mountainous, with approximately 73% of its total land area classified as sloped terrain. The region is characterized by complex geological conditions, short yet steep and fast-flowing rivers, and a high susceptibility to natural disasters. During the summer and autumn seasons, typhoons and heavy rainfall frequently trigger landslides in mountainous areas, posing significant risks to infrastructure and communities. While numerous studies have investigated landslide susceptibility in this region, few have examined the impact of different geoid models on these analyses. In Taiwan, geoid models are periodically updated, and these changes can influence key analytical factors in landslide susceptibility assessments, potentially affecting the outcomes. This study utilizes high-resolution digital elevation models (DEMs) based on various global geoid models, such as EGM96 and EGM2008, as well as regional geoid models like TWGEOID2014, TWGEOID2023, and TWGEOID2024, to assess their influence on landslide susceptibility. This study focuses on the mountainous areas of central Taiwan, which also exhibit the largest differences in geoid models. Logistic regression analysis is performed using IBM SPSS statistics software, incorporating terrain factors such as aspect, slope, curvature, relief, and roughness to evaluate landslide susceptibility. Landslide susceptibility maps and receiver operating characteristic (ROC) curves are generated for each geoid model and compared to assess their differences. The findings of this research aim to improve the precision of disaster prediction and provide valuable insights for disaster prevention efforts, soil and water conservation, and integrated risk management strategies. Additionally, this study highlights the importance of geoid model selection in geospatial analyses and its broader implications for environmental and engineering applications.

How to cite: Fang, K. H., Yang, Z. Y., and Hsiao, Y. S.: Evaluating the Impact of Geoid Model Variations on Landslide Susceptibility: A Case Study in Taiwan's Mountainous Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1820, https://doi.org/10.5194/egusphere-egu25-1820, 2025.

Tidal forces represent a significant external influence on Earth's deformation and have been extensively studied, beginning with Lord Kelvin (W. Thomson, 1862), who first calculated the elastic deformation of a homogeneous, incompressible Earth under tidal forces. Later, Love (1911) extended this work by developing a formalism for a compressible, homogeneous, spherical, non-rotating elastic isotropic Earth (SNREI), introducing the concept of Love numbers to describe tidal effects through dimensionless parameters. The Earth's visco-elastic deformation due to tidal forces is typically modeled using Maxwell, and less frequently, Burgers rheologies in the mantle. In this work, we perform a comparative analysis of four major rheological models—Maxwell, Burgers, Andrade, and Sundberg-Cooper—to evaluate their efficacy in describing Earth's rheological behavior. While Andrade and Sundberg-Cooper models are rarely applied to Earth, they have demonstrated effectiveness in modeling the visco-elastic tidal response of planetary bodies and satellites. We have developed theoretical responses for each of these models from seismic frequencies to very long periods. We first compare the advanced Andrade (1910) and Sundberg-Cooper (2010) models with the more traditional Maxwell and Burgers models. We then focus on tidal responses by comparing predicted gravimetric factors for these models with those observed from long-term gravimetric data collected by superconducting gravimeters within the IGETS (International Geodynamics and Earth Tide Service) network and by SLR (Satellite Laser Ranging).

How to cite: saad, T., Rosat, S., and Boy, J.-P.: Earth’s Tidal Response for Maxwell, Burgers, Andrade and Sundberg-Cooper rheological models of the mantle , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2012, https://doi.org/10.5194/egusphere-egu25-2012, 2025.

In this work we present a new method of determining the disturbing potential T and its functionals without using the Laplace equation.

The first step of this method is to solve two Dirichlet boundary value problems on the surface of the geoid related to a new partial differential equation (created by the author) named as G – modified Helmholtz equation. The solutions are formed after spherical approximation and describe gravity anomaly Δg and gravity disturbance δg as series of spherical harmonics.

In the second step we determine the disturbing potential T as a solution of a Dirichlet boundary value problem on the same boundary surface related to a very simple partial differential equation. Its Dirichlet boundary condition is formed with the aid of gravity anomaly, gravity disturbance and the fundamental boundary condition in spherical approximation. The solution is expressed as a series of spherical harmonics. As an epilogue to this work we present some new formulae for normal gravity γ, gravity g, vertical gradient of gravity, and mean curvature for actual equipotential surfaces as series of spherical harmonics.

The difference between known spherical harmonics and the introduced spherical harmonics is that the latter has the polar distance r in irrational powers. The advantage of this method is the simple determination of gravity anomaly, gravity disturbance and disturbing potential since it involves only Dirichlet boundary value problems. Finally this method shows that the determination of gravity anomaly and gravity disturbance can be made without determining the disturbing potential.

How to cite: Manoussakis, G.: Determination of the Earth’s disturbing potential and its functionals as series of spherical harmonics, without using the Laplace equation. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2088, https://doi.org/10.5194/egusphere-egu25-2088, 2025.

In regions with complex terrain, terrain correction is essential for accurately computing geoid undulations. The accuracy of Digital Terrain Models (DTMs), which include both terrestrial and marine datasets, has a significant impact on terrain correction and geoid modeling. One striking example is the coastal region of Hualien in eastern Taiwan, located at the land-sea boundary. This area is renowned for its dramatic topographical shifts, where elevations plummet from over 2000 meters above sea level to ocean depths exceeding 2000 meters within just a few kilometers. This study evaluates the effects of various global and regional Digital Elevation Models (DEMs) and Digital Bathymetric Models (DBMs) on geoid modeling in Hualien. The geoid modeling strategy utilizes a remove-restore approach, combining global geopotential models, local gravity observations, and high-resolution DEMs and DBMs. Particular attention is given to the accuracy of these DEMs and DBMs at the critical land-sea interface, where topographic variations are most pronounced. To validate the results, we compare them against high-resolution satellite imagery and the Global Self-consistent, Hierarchical, High-resolution Geography Database (GSHHG) coastline data. Additionally, geoid models derived from different DEM-DBM combinations are assessed using high-precision GNSS-leveling geometric geoid observations at multiple locations within the study area. The primary aim of this research is to improve terrain correction accuracy in areas with complex topography along land-sea boundaries, ultimately enhancing the precision and reliability of geoid modeling results.

How to cite: Yang, Z. Y., Fang, K.-H., and Hsiao, Y.-S.: Assessing the Influence of DEM and DBM Accuracy on Geoid Modeling at the Land-Sea Interface: A Case Study in Eastern Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2128, https://doi.org/10.5194/egusphere-egu25-2128, 2025.

Earth’s gravity field parameters can be derived from the perturbations of Keplerian orbit parameters. For example, even-degree zonal harmonics cause secular rates of the right ascension of the ascending node, whereas odd-degree zonal harmonics cause long-term periodic perturbations of the argument of perigee. The observations of changes in these Keplerian parameters can be used to derive Earth’s potential parameters. We investigate the relationship between the orbit perturbations as a function of the satellite height, inclination angle, and eccentricity to find optimum orbit parameters for the gravity field recovery which maximize the orbit perturbations. We employ the Kaula theorem of orbit perturbations based on the expansion of the gravity potential into trigonometric series and derive inclination F(i) and eccentricity functions G(e) for zonal even and odd-degree spherical harmonics. We also employ the satellite visibility function to find the optimum satellite height for the recovery of the global gravitational constant product GM, degree-1 spherical harmonics corresponding to the geocenter motion, Earth’s oblateness term C₂₀, and other low-degree harmonics.

We found that the optimum heights of satellites for GM, geocenter, and degree-2 are in the areas where no geodetic satellites currently are; i.e., between 1700 and 3500 km. The best inclination angles for the even-degree harmonic recovery are in the range of 20-40 degrees for prograde or 140-160 degrees for retrograde orbits. The best separability of odd-degree harmonics is for critical inclinations (63.4, 116.6 deg) or high eccentricities. C₃₀ can be well determined from a satellite at the inclination of 40 or 140 degrees at the height of 1400 km. To support future GRACE/MAGIC missions with C₂₀ and C₃₀, the best inclination would be about 40 or 140 degrees with a height of about 1500-1700 km.  Finally, the best height for superior geocenter recovery and determination of the gravitational constant is about 2300 – 3500 km, which is in between the LAGEOS-1/2&LARES-2 height (5800 km) and LARES-1&Ajisai height (1500 km).

How to cite: Sośnica, K., Zajdel, R., Najder, J., Kur, T., and Gałdyn, F.: Determination of Earth’s gravity field parameters based on orbit perturbations – theoretical approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2581, https://doi.org/10.5194/egusphere-egu25-2581, 2025.

Marine gravity anomalies arise from the interaction between seafloor topography and the isostatic adjustment of the lithosphere. The admittance function quantifies the ability to transform seafloor topography into gravity anomalies. By developing various admittance function models, the connection between lithospheric response-induced gravity anomalies and seafloor topography is established, facilitating the inversion of seafloor topography from marine gravity anomalies. Addressing the various geophysical parameters involved in the admittance function approach, this study used the CRUST1.0 model as a priori data and proposed the Moving Windows Admittance Technique, adopting a 40 km moving step and 600 km × 600 km window to invert an effective elastic thickness model at a resolution of 5′×5′. The “remove-restore” technique was also incorporated to enhance accuracy. In the Mariana Trench region, the study revealed that the trench-arc-basin system exhibits anomalously low lithospheric strength (effective elastic thickness around 2 km), whereas the subducting plate demonstrates greater strength. The constructed seafloor topography model was verified with shipborne bathymetric data, demonstrating accuracy comparable to the DTU18 model and outperforming the SIO V23.1 model (about 36.5% improvement). These findings highlight that optimizing geophysical parameters significantly enhances the accuracy of seafloor topography inversion, providing critical insights for future oceanic research.

How to cite: Shen, R. and Zou, X.: Advances in Seafloor Topography Inversion: Integrating Admittance Functions and Geophysical Parameter Optimization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2645, https://doi.org/10.5194/egusphere-egu25-2645, 2025.

We use data from the GRAIL and LRO satellite missions to estimate the horizontally varying density of the lunar crust. We determine the density model by parametrising the density using spherical harmonic functions up to degree 400. The density estimate depends on the difference between the data from the global gravitational field model generated by the topography measured by the LOLA sensor and the data from the GL1500E global gravitational field model derived from the GRAIL mission. To reduce the numerical complexity of the calculations, we approximate the topography by a sphere and test the sensitivity of the density estimates to the size of the spherical radius. We further calculate a global gravitational field model generated by the estimated horizontally varying density and the LOLA topography. We analyse the results by admittance, correlation, and Bouguer fields for degrees 150-600. The highest agreement with the input data is obtained for the approximating sphere identical to its Brillouin counterpart. Overall, the horizontally varying density model provides a more realistic gravitational field than the one from the constant crustal density. The advantages of the applied approach lie in the speed of calculation, low requirements on hardware, and ease of implementation.

How to cite: Šprlák, M. and Perkner, V.: Lunar crustal density estimate from the GRAIL and LOLA-based global gravitational field models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2861, https://doi.org/10.5194/egusphere-egu25-2861, 2025.

Geothermal energy is a significant source of clean, renewable energy, and the Bavarian Molasse Basin demonstrates exceptional potential for its development. Over the past two decades, the region has made remarkable progress in harnessing geothermal energy. Between 1998 and 2021, a total of 30 deep geothermal energy projects were implemented in Bavaria, with 24 systems currently in operation.  Munich is a leader among European cities in utilizing centralized geothermal systems, with plans to fully cover the city’s energy needs through geothermal resources by 2040.

However, the operation of geothermal power plants can induce seismic activity and alter the stress-strain state of the subsurface, posing potential threats to the environment and population. Induced seismicity is a key issue for geothermal projects worldwide, where its occurrence has caused significant delays in development and, in some cases, damage to buildings and infrastructure.

To evaluate the impact of geothermal activity on surface deformation, we processed a dense network of Sentinel-1 interferograms (2018-2021) using Small Baseline Subset (SBAS) InSAR time-series analysis through NASA's Alaska Satellite Facility (ASF) OpenSARLab. This approach enabled us to generate high-precision cumulative displacement and velocity maps across Munich and its surrounding areas over the three-year period.

Our analysis revealed localized ground uplift throughout the region, with pronounced deformation rates near certain geothermal plants, in some cases reaching a few cm/year. These uplift patterns appear to correlate with geothermal operations, particularly reservoir pressure changes and fluid reinjection.  In contrast, areas of subsidence, observed away from geothermal sites, appear to result from natural geological processes such as sediment compaction, groundwater extraction, and karstification.

These findings are vital for seismic hazard assessments, as surface deformation is closely tied to induced seismicity in geothermal environments. The study underscores the importance of advanced geodetic monitoring techniques, such as InSAR, for evaluating seismic risks and ensuring the sustainable development of geothermal energy resources.

How to cite: Semenova, Y., Seitz, M., Bloßfeld, M., and Seitz, F.: Geodetic monitoring of surface deformation for mitigating induced seismicity in Bavarian geothermal operations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4198, https://doi.org/10.5194/egusphere-egu25-4198, 2025.

The spectral combination method or technique encompasses all procedures to combine heterogeneous datasets by spectral weights, which depend on spherical harmonic degree n. This method was developed primarily to combine a global geopotential model (GGM) with terrestrial gravity data that is transformed into the gravity potential by integral formulas. Later, this method was extended to combine solutions to boundary-value problems (BVPs). The spectral combination method is based on the stochastic characteristics of measured gravity data, i.e., their signal and error degree-order variances. This technique represents the integral transform, in which the integral kernel is modified by spectral weights determined by the least-squares method.

So far, the spectral combination method has been applied only to solutions to spherical BVPs. In this contribution, we extend this method to solutions of vertical and horizontal spheroidal BVPs. Solutions of vertical and horizontal spheroidal BVPs for the gravitational potential have been presented by (Šprlák and Tangdamrongsub, 2018). Here, we derive corresponding solutions of vertical and horizontal spheroidal BVPs for first-, second- and third-order directional derivatives. Secondly, we derive the spectral weights for the corresponding solutions of vertical and horizontal spheroidal BVPs. Finally, we check the numerical correctness of the derived solutions of vertical and horizontal spheroidal BVPs and spectral weights in a closed-loop test with data from GGM.       

How to cite: Pitonak, M., Belinger, J., Novak, P., and Sprlak, M.: Downward continuation of the gravitational gradient components to gravitational field quantities by spheroidal spectral combination technique, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4271, https://doi.org/10.5194/egusphere-egu25-4271, 2025.

In recent years, the number of space objects has been increasing rapidly. It has become crucial to utilize multi-source information fusion techniques for the orbit measurement and cataloguing of numerous objects. This report elaborates on the utilization of ground-based radar, optical, and space-based optical measurements in joint precision orbit determination. Regarding the real-time surveillance of a vast amount of space debris, investigations have been conducted concerning the initial orbit determination upon the first detection of targets, data association, orbit refinement, and the generation of catalogued orbital elements.Space-based technologies assume a particularly crucial role owing to their remarkable advantages in temporal and spatial coverage. To fulfill the data processing requisites for orbit determination of space-based measurement platforms, the onboard GNSS precision orbit determination software, SODA, has been developed, attaining centimeter-level accuracy in orbit determination. In the scenario of long-arc tracking via ground single-station astronomical optical cameras, an orbit determination accuracy within the range of several tens of meters can be accomplished. In the situation where multiple satellites are equipped with optical cameras, a substantial enhancement in the monitoring performance of space debris can be achieved both temporally and spatially.

How to cite: Yezhi, S.: Integrated Space-Based and Ground-Based Space Debris Orbit Determination, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4408, https://doi.org/10.5194/egusphere-egu25-4408, 2025.

The least-squares method is commonly utilized to address data processing problems. The "adjustment in steps" technique is used in this study to optimize the "adjustment of measurements only" method. We use an initial set of condition equations of a mathematical model, to compute the initial best estimates of a given set of measurements. Subsequently, we may add or remove conditions from either the same model or a new form of it. The final solution is produced by revising the initial estimations of the measurements without applying the adjustment procedure to the entire system of condition equations. This technique is generalized in several steps. Each stage involves revising measurement estimates. The splitting of the solution system into steps simplifies the adjustment procedure because each step includes the multiplication and inversion of smaller matrices than those used for the complete system. Furthermore, the efficiency of this technique as a function of the number of steps taken is examined. The smallest amount of computations required to handle a large number of measurements yields the best solution. Finally, nonlinear condition equations are investigated. Numerical experiments are used to validate the theoretical concepts.

How to cite: Koci, J. and Panou, G.: Adjustment of a large number of measurements in steps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4725, https://doi.org/10.5194/egusphere-egu25-4725, 2025.

In our research, we propose a novel numerical approach based on the finite element method applied for modelling time variations of global Earth’s gravity field in the space domain. As input data we use the GRACE-FO satellite gravity data which are prolonged and filtered on the Earth's surface, while the Earth's surface is determined by digital elevation model on lands and mean sea surface obtained by satellite altimetry. Then the surface gravity disturbances on the Earth's surface serve as the boundary condition for the geodetic boundary value problem. Away from the Earth we involve the so-called mapped infinite elements which naturally prescribe the regularity of the disturbing potential at infinity. Afterwards, the obtained solution is determined at every moment when new input data is applied. In this way, we dynamically determine the Earth's gravity field on and above the Earth's topography.

How to cite: Minarechová, Z., Macák, M., Korekáčová, B., and Čunderlík, R.: Modelling time variations of global gravity field by the finite element method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4804, https://doi.org/10.5194/egusphere-egu25-4804, 2025.

The poster discusses the solution of the Poisson equation for the gravitational potential of irregularly shaped bodies by the finite element method (FEM) in ANSYS software. The aim of this research is to study whether the FEM can overcome the limitations of the spherical-harmonic-based approaches, namely their divergence in the vicinity of the gravitating body. The objects of investigation are three asteroids: 433 Eros, 25143 Itokawa and 101955 Bennu. The computational domain is a sphere with a radius 10 times larger than the average radius of the selected asteroid, at the origin of which the given asteroid is located. The input to the computation is the density of the asteroids, while outside the asteroid zero density is considered. The output is the gravitational potential and gravitational acceleration in the vicinity of the asteroids. The results of the computations are compared with the solutions by the spherical and spheroidal harmonic-based approaches.

How to cite: Macák, M. and Minarechová, Z.: Application of the finite element method to the modelling of the gravitational field of asteroids, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4830, https://doi.org/10.5194/egusphere-egu25-4830, 2025.

Modeling the gravitational effects of the topography and other layers of the Earth’s interior is one of the fundamental topics in geodesy and geophysics. Previous formulas of the Gravitational Potential (GP), Gravitational Vector (GV), and Gravitational Gradient Tensor (GGT) of a vertical cylindrical prism were derived from complex conversion relations and were relatively complicated. In this contribution, we derive the optimized formulas through a particular geometrical relation between the computation point and integration point, which are consistent with the previous expressions. The analytical formulas of the GP, GV, and GGT of a cylindrical shell are presented when the computation point is located on the polar axis. Based on these formulas, a cylindrical shell benchmark is put forward to evaluate the numerical properties of the cylindrical prism, that is, to discretize a whole cylindrical shell into cylindrical prisms. Beyond the improved simplicity, our optimized formulas with a second-order 3D Taylor series expansion help to save computation time (particularly for the GGT up to 20%). Numerical results reveal that when the computation point's vertical distance changes, the relative and absolute errors are symmetric with respect to the center vertical distance of the cylindrical shell. Accompanying codes in Python for a vertical cylindrical prism and a cylindrical shell are provided at https://www.github.com/xiaoledeng/optimized-formulas-of-gp-gv-ggt.

How to cite: Deng, X.-L., Sneeuw, N., and Tsoulis, D.: Optimized formulas of the gravitational field of a vertical cylindrical prism, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5583, https://doi.org/10.5194/egusphere-egu25-5583, 2025.

We present 3D numerical modelling of the altimetry-derived marine gravity data with the high horizontal resolution 1 x 1 arc min. The finite volume method (FVM) as a numerical method is used to solve the altimetry-gravimetry boundary-value problem. Large-scale parallel computations result in disturbing potential in every finite volume of the discretized 3D computational domain between an ellipsoidal approximation of the Earth’s surface and upper boundary chosen at altitude of 200 km. Afterwards, the first, second or third derivatives of the disturbing potential in different directions are numerically derived using the finite differences. A process of preparing the Dirichlet boundary conditions over ocean/seas has a crucial impact on achieved accuracy. It is based on nonlinear filtering of the geopotential generated on a mean sea surface (MSS) from a GRACE/GOCE-based satellite-only global geopotential model.

   We present different types of the altimetry-derived marine gravity data obtained on the DTU21_MSS as well as at higher altitudes of the 3D computational domain. The altimetry-derived gravity disturbances on the DTU21_MSS are tested by shipborne gravimetry and compared with those from the recent datasets like DTU21_GRAV or SS_v31.1. The obtained altimetry-derived gravity disturbances at higher altitudes are compared with airborne gravity data from the GRAV-D campaign in US. The gravity disturbing gradients as the second derivates or the third derivatives are provided with the same high resolution on the DTU21_MSS as well as at different altitudes.

How to cite: Čunderlík, R., Macák, M., Kollár, M., Minarechová, Z., and Mikula, K.: 3D high-resolution numerical modelling of altimetry-derived marine gravity data using FEM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5601, https://doi.org/10.5194/egusphere-egu25-5601, 2025.

The gravity field of a level oblate spheroid is formulated in this study using various coordinate systems. From the viewpoint of physical characteristics, it is assumed that this ellipsoid of revolution encloses mass, rotates with constant angular velocity and is a level (or equipotential) surface of its own gravity field. First, a spheroidal coordinate system and spheroidal harmonics are introduced. An exterior Dirichlet boundary-value problem is solved to determine the gravitational potential. As a result, the gravity potential is calculated completely and uniquely outside of the ellipsoid. Its closed form is then given in Cartesian, spherical, and geodetic coordinates. The gravity vector is calculated from the gravity potential in the exterior space and on the surface of the level ellipsoid. Additionally, the classical theorems of Clairaut, Pizzetti, and Somigliana are presented. Second, because the Earth's ellipsoid deviates slightly from a sphere, series expansions in terms of eccentricities for the normal gravity field are provided. Finally, the field is expanded in terms of spherical harmonics, which are useful for interpretations and calculations.

How to cite: Panou, G. and Marti, U.: New formulation for the normal gravity field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5919, https://doi.org/10.5194/egusphere-egu25-5919, 2025.

Knowledge of the potential difference (altitude above sea level H^γ) or spatial position (ellipsoidal height H) at the measurement point leads to two main types of free-air gravity reduction: anomalies Δg and disturbances δg.
This gives rise to geodetic boundary problems of determining the external anomalous potential T or its transformants (on the Earth's boundary surface S and beyond it), which are solved, in particular, using a family of functions orthogonal on a geometrically regular surface maximally close to the boundary surface (a sphere Ω or an oblate ellipsoid); in a more general case, the apparatus of integral equations should be used (for example, with respect to the density of a simple layer φ, which explains the external anomalous field).
When the anomalous potential is found from the solution of one boundary value problem, it is possible to transform it to a gravity reduction corresponding to another boundary value problem.

In modern conditions, a situation is theoretically and practically possible when both the normal H^γ and geodetic H heights are known, thus, the anomalous potential T itself at a point on the Earth's surface is considered known, the accuracy of its calculation in a linear measure is limited by the accuracy of knowledge of the heights (the first centimeters).
Further, calculations of the elements of the anomalous field can be formally performed based on the solution of the first boundary value problem, but an increase in the order of the derivative of the anomalous potential leads to a loss of accuracy during the next differentiation.
Therefore, as initial data, it is better to have such a derivative whose order is as close as possible to the desired value, so that the relevance of gravity measurements does not decrease.

As a result of such measurements complex, it is possible to calculate separately the Δg and δg.
It is generally believed that calculations using δg lead to a more accurate result due to the known boundary surface (although using the potential difference instead of the spatial position is more justified from a physical point of view).
But which type of gravity reduction would be optimal?

Solution of the geodetic boundary value problem for determining the anomalous potential T at an external point P has a very simple form in the spherical approximation if we introduce a special gravity reduction Πg with the corresponding boundary condition on the Earth's surface S:

The integration kernel 2/r is convenient because it does not contain the natural logarithm.

It is of interest to derive a more accurate boundary condition taking into account Earth's flattening.

Also, in spherical approximation, one can obtain an integral equation (*), which is significantly simpler than the integral equations (**) and (***):

The simplicity of such a gravity reduction was first noted by L.P.Pellinen and O.M.Ostach in their article on some topographic gravity anomalies. See: Stud Geophys Geod 18, 319–328 (1974), https://doi.org/10.1007/BF01627186

How to cite: Popadyev, V. and Alena, D.: Optimal gravity reduction when anomalous potential is known, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6301, https://doi.org/10.5194/egusphere-egu25-6301, 2025.

To establish the gravity database for the African geoid, it is needed to remove the blunders from the available gravity data set. As the available gravity data for Africa is very limited, including large data gaps, the gross errors detection technique should be smart enough to eliminate only the real blunders. A smart gross error detection technique has been adopted. It is based on the least squares prediction algorithm. The technique works first to estimate the gravity value at the data station using other values than the current data point. It thus compares the estimated value to the data value for possible blunder detection. Hence the technique measures the influence of removing the data value of a current point on the neighbourhood stations. Only if the value of a certain station proves to be blunder, it is then removed from the data base. Another effective technique to estimate the blunder in the gravity database of Africa is designed using the Artificial Intelligence. The results of both gross errors detection techniques are compared and analyzed in order to give a proper judge on both algorithms.

How to cite: Abd-Elmotaal, H. and Kühtreiber, N.: Gross Errors Detection for the African Gravity Database, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6382, https://doi.org/10.5194/egusphere-egu25-6382, 2025.

Accurate monitoring of sea level variations is crucial for understanding climate change impacts and supporting coastal management. However, traditional methods like tide gauges and satellite altimetry face limitations in coverage and precision. This research explores the capabilities of GNSS/IMU buoy systems for enhancing sea surface height measurements and depth datum assessments. By deploying GNSS/IMU buoys near 34 tide gauge stations across Taiwan, a comparative analysis was conducted to examine the reliability and precision of these innovative tools against conventional tide gauge data. Utilizing advanced loosely coupled GNSS/IMU integration of GNSS and IMU data, the study achieves centimeter-level accuracy in dynamic marine conditions. Results reveal that while most tide gauges are consistent with the buoy data, significant discrepancies are observed at a few stations, particularly in subsidence areas and offshore islands. This study underscores the potential of GNSS/IMU buoy systems as a cost-effective and flexible solution to complement tide gauges, especially in regions affected by vertical land motion. The findings advocate for broader adoption of GNSS/IMU technologies to improve coastal and offshore hydrographic observations under changing environmental conditions.

How to cite: Kuo, C.-Y., Lan, W.-H., Lee, C.-M., Kao, H.-C., and Tseng, T.-P.: Enhancing Sea Surface Height Monitoring and Depth Datum Assessment Using GNSS/IMU Buoy Systems: A Case Study of Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7740, https://doi.org/10.5194/egusphere-egu25-7740, 2025.

Accelerometers have been widely used in almost every area of science and engineering. They are supposed to be physical instruments for measuring the acceleration of a moving object. Although huge technological advance is made in hardware of accelerometers over more than one century, accelerometers have been persistently designed and fabricated mechanically under the framework of forward problems of damped mass–spring systems. We show that accelerometers are essentially inverse ill-posed source problems from the mathematical point of view, implying that small measurement errors of equivalent displacements are inherently amplified significantly such that accelerations output from accelerometers can become extremely noisy, numerically incorrect and physically meaningless. The ill-posedness of accelerometers has been always implicitly circumvented approximately for more than one century. As a result, accelerometers theoretically can only produce approximate outputs of acceleration. Here we present the concept of computerized accelerometers, because inverse ill-posed problems, as in the case of accelerometers, cannot be rigorously solved mechanically. The acceleration can only rigorously be reconstructed computationally as a regularized solution to the inverse ill-posed source problem of acceleration from equivalent displacements. The concept of computerized accelerometers theoretically warrants precise measurement of acceleration without approximation, is valid for nonlinear time-dependent damping as well and provides a turning point for accelerometers to become a fully rigorous computerized physical instrument. Simulated examples have confirmed that least squares reconstruction of acceleration can be too extremely noisy to be physically meaningful and shown that elastic acceleration is incorrect by more than 100%.

How to cite: Xu, P.: Concept of computerized accelerometers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7936, https://doi.org/10.5194/egusphere-egu25-7936, 2025.

Genesis is an ESA-approved mission dedicated to GNSS Science conducted by the ESA Navigation Directorate. Its primary objective is the contribution to the improvement of the International Terrestrial Reference Frame (ITRF) accuracy (1mm) and long-term stability (0.1mm/year). Secondary objectives include the contribution to a high number of other scientific disciplines (geodesy, geodynamics, earth rotation, geophysics, earth gravity field, atmosphere and ionosphere sciences, metrology, relativity…) [1].

The Genesis Space Segment includes a single spacecraft in MEO (6000km altitude, 95° inclination) co-locating for the first time in space the four geodetic instruments used for the realisation of ITRF: a GNSS receiver, an SLR reflector, a VLBI transmitter and a DORIS receiver. The Ground Segment is composed of a Mission Control Centre (including Ground Station) and will make use of the existing ground infrastructure, operated by the Scientific Community: GNSS sensor stations network, SLR stations, VLBI antennas and DORIS beacons. The scientific mission data will be processed, archived, and distributed by ESA’s Data PROcessing, Archiving and Delivery facility (PROAD), under the responsibility of the Navigation Support Office and the GNSS Science Support Centre, in close collaboration with the scientific community.

Genesis mission will implement a unique dynamic space geodetic observatory, allowing an extraordinary combination of innovative technology and fundamental science. As the ITRF is recognised to be the foundation for all space- and ground-based space mission activities, Genesis will have a major impact on almost any space missions and, in particular, on Navigation and Earth Science.

On the industrial side, the company OHB Italia has been contracted by ESA as prime for the development, qualification, launch and 2 years operation of the mission, with a launch date in 2028 [2]. Antwerp Space (B), as the major sub-contractor of OHB-I, oversees the payload and geodetic instruments. Industrial activities were kicked-off in April 2024, the System Requirements Review was successfully closed-out in Q4 2024, and work is on-going towards a Preliminary Design Review in Q4 2025.

In parallel, on the scientific side, after a successful Genesis Workshop held in February 2024 [3], a Genesis Science Team was set-up and members appointed. This structure includes representatives of ESA, a lead Scientific Coordinator and Co-Coordinator, as well as five Working Groups covering the four geodetic techniques and their combination. Genesis Science Team has been actively supporting the mission development (in particular consolidation of requirements) and will play a key role in its future exploitation.

The paper will provide a detailed description of the scientific objectives, mission, and system overview, and a programmatic status of the Genesis Mission.

[1]: Delva et al. Earth, Planets and Space 75, 5 (2023)

[2]: https://www.esa.int/Applications/Satellite_navigation/ESA_kicks_off_two_new_navigation_missions

[3]: https://www.esa.int/Applications/Satellite_navigation/The_geodetic_community_meets_Genesis

How to cite: Fusco, G., Gidlund, S., Waller, P., Morlet, C., Perez Lissi, F., Sakalauskaite, E., Enderle, W., Schoenemann, E., Berton, J.-C., Gini, F., and Navarro, V.: Genesis: A Unique Space Geodetic Observatory, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8240, https://doi.org/10.5194/egusphere-egu25-8240, 2025.

Seafloor topography prediction plays a crucial role in filling data gaps in regions lacking ship sounding measurements. However, the reliance of prediction algorithms on ship sounding data varies significantly. This study evaluates the impact of ship sounding coverage and distribution on the prediction accuracy of two methods: the gravity–geologic method (GGM) and an analytical algorithm. Simulation experiments reveal that increasing the ship sounding coverage from 5.40% to 31.80% and achieving a more uniform distribution significantly enhance the accuracy of the GGM, reducing the RMS error from 238.68 m to 42.90 m (an improvement of 82.03%). In contrast, the analytical algorithm maintains a stable RMS error of 40.39 m, demonstrating independence from ship sounding data. Further analysis in a 1° × 1° sea area (134.8°–135.8°E, 30.0°–31.0°N) shows that higher ship sounding coverage (33.19%) reduces the GGM RMS error from 204.17 m to 126.95 m compared to lower coverage (8.19%). However, the analytical algorithm's RMS error remains consistent at 167.94 m. These results underscore the GGM's sensitivity to ship sounding data and the analytical algorithm's robustness. The findings highlight the importance of combining algorithms based on ship sounding coverage. For regions where coverage exceeds 30%, the GGM offers superior accuracy. Conversely, the analytical algorithm performs better in low-coverage scenarios. This study provides a basis for integrating multiple algorithms to enhance global seafloor topography models.

How to cite: Tian, Y., Yu, J., and Xu, H.: Comparison of Seafloor Topography Prediction Using the Gravity-Geologic Method and Analytical Algorithm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8273, https://doi.org/10.5194/egusphere-egu25-8273, 2025.

The standard theoretical framework for the gravitational field determination often relies on spherical approximation. However, Earth’s shape is much closer to a rotational ellipsoid flattened at the poles, as proved by the legendary expeditions of the French Academy of Sciences to South America and Lapland already in the 18th century. Contemporary investigations of solar system planetary bodies have revealed that many resemble prolate or oblate ellipsoids, whereas a high amount of them is flattened more significantly than the Earth. Four such spheroidal bodies have recently been subject to immense research interest: 1) Mars being explored by satellite and lander missions as it represents a potential target for future colonisation, 2) the asteroid Bennu explored by the sample-return satellite mission OSIRIS-REx, 3) the dwarf planet Ceres, and 4) the asteroid Vesta, both explored by the satellite mission Dawn. Moreover, several comets and asteroids with spheroidal (ellipsoidal) shapes have been subjected to intense small-body research. Consequently, there is an urgent need to formulate a modern theoretical framework for the gravitational field determination.

In this contribution, we formulate a mathematical theory for modelling of gravitational fields generated by ellipsoidal bodies. In addition, we present both theory and software considering non-singular solution for derived equations using recurrences instead of classical approach, which depends on reduced spheroidal latitude. Using recurrences, we can eliminate singularities on poles and computational errors in their proximity caused by latitude dependence.

How to cite: Belinger, J., Dohnalova, V., Pitonak, M., Novak, P., and Sprlak, M.: Global gravitational field modelling for spheroidal planetary bodies: non-singular solutions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10368, https://doi.org/10.5194/egusphere-egu25-10368, 2025.

Recent advancements in geodesy have highlighted the dynamic interplay between theory, science, engineering, technology, and practice-oriented services. The continuous evolution of geodetic science has led to significant progress in both traditional geodetic challenges and emerging issues, often driven by innovations in instrumentation and computational techniques. This paper explores the potential to enhance airborne gravimetry by incorporating data from typically discarded flight segments—such as takeoff, landing, and turning periods—referred to as "preparing time" or "junk periods." While these phases are often excluded due to complexities in modeling aircraft accelerations, this study demonstrates the value of including this data in local gravity field modeling. Through simulations of gravity disturbances and rigorous downward continuation methods, we achieve significant improvements in precision (57%, 17%, and 12%) for data in the bandwidth from spherical harmonic degrees 200 to 1080. Notably, further improvements (55%, 41%, and 30%) are observed when extending the bandwidth from spherical harmonic degrees 1080 to 2160. This research emphasizes the importance of utilizing the entire flight trajectory to improve airborne gravimetry efficiency. The findings have implications for the integration of advanced technologies, such as quantum gravimeters with sub-mGal accuracy, as well as the coupling of various gravimetric systems, including vector gravimetry, to solve complex geodetic problems.

How to cite: Li, X.: Unlocked Potentials in Airborne Gravimetry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11128, https://doi.org/10.5194/egusphere-egu25-11128, 2025.

New devices often come along with new data structures and formats, and new instrument technologies require a new method of data processing. In recent years, BKG and GFZ have operated novel absolute quantum gravimeters (AQG) by Exail (formerly Muquans) in different environments for geodetic and hydrological applications. Here we present a newly released open-source library “gravitools” [1] we have developed for the handling and post-processing of AQG raw data.

The library is designed as a toolbox of data structures for common data handling, but also routines for standardized processing. For this new instrument there is yet no agreed upon standard method for these two aspects. With gravitools, we aim at providing a solid approach to address this topic and actively contribute to the necessary development of such a standard within the gravimetry community. In order to enhance usability, gravitools was developed as a user-friendly, reliable software application both for non-experts and advanced users. To this end, it offers a command-line, scripting and graphical user interface, which provides advanced users the option to precisely define their individual settings and routines. This contribution will provide an overview of implemented key features and their usage (data handling, processing, visualizing, documenting and archiving) as well as an outlook of planned extensions, such as the integration of similar features for CG-6 gravimeters.

The gravitools library It is written purely in Python and released on the Python Package Index (PyPI). It is licensed as open-source to make it freely available to the scientific community and encourage feedback and contributions.

[1] gravitools: https://gitlab.opencode.de/bkg/gravitools

How to cite: Reich, M., Glässel, J., Wziontek, H., and Güntner, A.: gravitools: an open-source toolbox in Python for post-processing Exail Absolute Quantum Gravimeter (AQG) and other terrestrial gravimeter data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11169, https://doi.org/10.5194/egusphere-egu25-11169, 2025.

The structure of the Laplace operator is relatively simple when expressed in terms of spherical or ellipsoidal coordinates. The physical surface of the Earth, however, substantially differs from a sphere or an oblate ellipsoid of revolution, even if optimally fitted. The same holds true for the solution domain and the exterior of a sphere or of an oblate ellipsoid of revolution. The situation is more convenient in a system of general curvilinear coordinates such that the physical surface of the Earth (smoothed to a certain degree) is imbedded in the family of coordinate surfaces. Therefore, a transformation of coordinates is applied in treating the geodetic boundary value problem. The transformation contains also an attenuation function. Subsequently, tensor calculus is used and the Laplace operator is expressed in the new coordinates. Its structure becomes more complicated now. Nevertheless, in a sense it represents the topography of the physical surface of the Earth. For this reason the Green’s function method is used together with the method of successive approximations in the solution of the geodetic boundary value problem expressed in terms of the new coordinates. The structure of iteration steps is analyzed and if possible, it is modified by means of integration by parts. The iteration steps and their convergence are discussed and interpreted. The approach is also compared with the method of analytical continuation.

How to cite: Holota, P.: Divergence of the gradient, solution domain geometry and successive approximations in gravity field studies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12189, https://doi.org/10.5194/egusphere-egu25-12189, 2025.

Since April 2024 the Conrad observatory, located 60 km SW of Vienna within a karstic area of the Eastern Alps (Austria), operates a superconducting iGrav gravimeter (iGrav050) continuing the previous more than 10 years long gravity time series of GWR C025. Their gravity residuals indicated an extremely complex local hydrology in the surroundings of the observatory. For better understanding the local hydrological processes a geoelectric profile has been installed which monitors a 2D resistivity section each day. The profile runs across the topography just above the gravimeter. The latter is an underground installation. The situation is challenging because the profile runs closely above cavities built up by the observatory’s underground labs and tunnel. In addition, the geoelectric settings are limited by the requirements of the nearby geomagnetic observatory.

In September 2024 an extraordinary rain event happened in Lower Austria with cumulative rain as large as 400 mm within a few days. First results are shown comparing the gravity signal with the time dependent resistivity sections providing insight to the water content within the terrain top layer. In addition, the gravity residual signals are compared to those originating from a snowmelt event in 2009 with similarly large water intrusion during short time as in September 2024.

How to cite: Arneitz, P., Meurers, B., Jochum, B., Ita, A., Ottowitz, D., Leonhardt, R., and Egli, R.: Gravity and 2D time lapse resistivity monitoring at Conrad Observatory for understanding local hydrology – case study of an exceptional rain event in September 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15367, https://doi.org/10.5194/egusphere-egu25-15367, 2025.

This study develops real-time continuous dynamic vertical reference for quantifying hydrodynamic processes with respect to high-resolution and accurate marine geoid model. In particular, this can now be realised through dynamic topography (DT), which is defined as the instantaneous sea surface height (SSH) deviation from the marine geoid (DT=SSH–geoid) and represents one of the most useful parameters of marine dynamics.

In regions of good quality and dense coverage of gravity data a 5 cm accurate marine geoid modelling is achievable. Due to the underlying accurate geoid model the DT values can now be estimated, eg. from a suitable hydrodynamic model, with the dm level accuracy. This corresponds to the most strict requirement for vertical accuracy at cargo handling in ports, dredging, maritime engineering, hydrography and under-keel clearance (UKC) management. This DT accuracy range also creates pre-conditions for identifying realistic sea level variations and circulation patterns of oceanic currents, seamlessly from the coastline toward the offshore over large basins.

Due to strict safety regulations various maritime and offshore applications require short term realistic sea level forecasts for hours to days in advance. Such near-real time DT estimations create a breakthrough opportunity for advancing from the “static” marine geoid referred vertical datum to the development of a new type vertical datum – a dynamic (both spatially and temporally) vertical reference frame. This continuous (and liquid!) DT field represents (either retrospectively or in the forecasting mode) the realistic sea level in absolute sense. Once DT is solved with sufficient accuracy then this dynamic DT field serves then as a reference (hence the name!) for developing further data products. These continuous DT field estimates are used for computing its spatio-temporal derivatives (eg. horizontal gradient), that might reveal ocean circulation patterns.

The Baltic Sea countries have been fortunate to have access to a wide range of marine data products, including that of a high-resolution marine geoid and hydrodynamic models that allow further capabilities to be explored in terms of sea level accuracy and validation. Accordingly, this study proposes a geodetic methodology that synergizes different sea level data sources by utilization of the marine geoid. The methodology applied utilized mathematical, statistical and machine learning strategies to obtain a spatio-temporally continuous dynamic topography of the Baltic Sea level. Sea level forecasting using DT is examined using machine learning approaches such as Convolution Neural Network. By using deep learning methods a DT modelling accuracy of within 10 cm has been achieved, which appears to better than the traditional data assimilation based forecasting.

Accomplishing this creates a marine dynamic vertical reference frame, which allows novel opportunities for marine digital twins, navigation, oceanographic processes and marine forecasting abilities.

How to cite: Ellmann, A., Delpeche-Ellmann, N., Varbla, S., Rajabi Kiasari, S., Jahanmard, V., and Kupavõh, A.: Development of continuous dynamic vertical reference for maritime and offshore engineering by applying geodetic and machine learning strategies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20596, https://doi.org/10.5194/egusphere-egu25-20596, 2025.

Signal separation is a general problem in many geodetic datasets representing the superposition of various sources. We investigate global, temporal gravity data such as measured by the satellite missions Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow on (GRACE-FO). As gravity is an integral quantity, these data include signal components related to all kinds of geophysical processes involving a redistribution of masses in the Earth’s system. Examples for the latter are water mass redistribution processes such as seasonal hydrological variations or extreme events, as e.g. floods and droughts, but also Earthquakes or mass changes of ice sheets.

For optimally exploiting temporal gravity data regarding geophysical downstream applications, algorithms splitting up the data into the contained sub-signals are required. We attempt solving this signal separation task by training a neural network-based algorithm to recognize the individual signal components based on their typical patterns in space and time. Thereby, prior knowledge on the spatio-temporal behavior of the individual signals is introduced via forward-modeled time-variable gravity data for each of the components, as well as additional constraints.

Our algorithm is based on a multi-channel U-Net architecture which takes the sum of several signals as input and gives the retrieved individual sub-components as output. For the supervised training and subsequent testing of our software, we use a closed-loop simulation environment, working with the time-variable gravity signals given by the Updated ESA Earth System Model. The latter includes separate datasets for temporal gravity signals caused by mass change processes in the atmosphere and oceans (AO), the continental hydrosphere (H), the cryosphere (I) and the solid Earth domain (S).

For converting the global, temporal gravity data depending on the axes latitude, longitude and time to a 2-d image data format fitting the input and output layers of the U-Net, we split the data along one of its three axes to obtain latitude-longitude, latitude-time or time-longitude samples.

In a test example, we investigate the task of separating the above-mentioned AO, H, I and S components from their sum. The resulting relative RMS test errors being between 19% and 67% demonstrate that our network successfully separates the four considered signals from their sum at signal-to-noise ratios larger than 1.

In our contribution, we describe the functionalities of our software and possibilities to adapt it to any task of interest, including methods for introducing additional physical knowledge on the behavior of specific signals. In general, the described framework is applicable for signal separation in any dataset that depends on three axes (e.g., two spatial and one temporal, or three spatial axes). For the real data application of the framework, we suggest to use representative forward-modeled signals for training, and to subsequently test the trained separation model on real observational data.

How to cite: Heller-Kaikov, B., Pail, R., and Werner, M.: Neural network-based framework for gravity signal separation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1481, https://doi.org/10.5194/egusphere-egu25-1481, 2025.

Small bodies such as asteroids, comets and moons are primary targets for space exploration. To test guidance, navigation and control algorithms an accurate model of the target’s gravity field is crucial for mission success. However, creating an accurate model near the body’s surface is a challenging task due to the often highly irregular shape and the limited information about the internal mass distribution.

This study presents a Convolutional Neural Network (CNN) to determine the density distribution from accelerations at the surface using gravity inversion. We used our voxel-based mascon simulation environment VMC to generate over 100k realistic density distributions (labels) for a cube and calculated the corresponding acceleration (features) for a fixed grid of positions. We selected this simplistic toy problem due to the perfect shape reconstruction and optimal data representation for the deep learning architectures. To investigate the effect of the shape mismatch between a voxel-reconstructed object and the real object we trained an additional Neural Network (NN) to extract the mass distribution for a triaxial ellipsoid using a similar amount of data.

We used a train/test ratio of 80/20 and trained both models using multiple hyperparameter sets for a maximum of 200 epochs using the Adam optimizer. After convergence, all models conserve the total mass. The best-performing architectures are able to determine the general trend of the mass distribution. For the ellipsoid, it can be observed that the model’s prediction is strongly influenced by the contribution of the body’s shape to the gravitational field.

Our results show that NNs are a promising candidate to extract the density distribution using gravity inversion.

How to cite: Haser, B., Andert, T., and Förstner, R.: Gravity Inversion using Convolutional Neural Networks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1723, https://doi.org/10.5194/egusphere-egu25-1723, 2025.

Recent advancements in Global Navigation Satellite System Reflectometry (GNSS-R) have led to significant progress in retrieving soil moisture (SM) and other land parameters such as Above Ground Biomass (AGB). The 2016 launch of NASA’s Cyclone GNSS (CYGNSS) mission provided high spatiotemporal resolution GNSS-R data, enabling more accurate soil moisture estimation. This is a key factor influencing the dielectric constant of scattering surfaces. Recent studies have demonstrated the effectiveness of Artificial Neural Networks (ANN) and Deep Learning (DL) models, including convolutional neural networks (CNNs), in addressing the non-linear complexities of soil moisture retrieval [1], [2]. In this study, CyGNSSnet, which was originally designed for global ocean wind speed estimation [3], is being adapted and optimized for global soil moisture estimation.

The research utilizes CyGNSS Level 1 version 3.2 data, specifically Delay Doppler Maps (DDMs), as the primary input. Each reflection point includes additional parameters like measurement geometry and reflectivity. Auxiliary datasets, including topography, soil texture, vegetation indices, and climate-related variables, are incorporated alongside SMAP soil moisture data as the target variable. These datasets, covering August 2018 to July 2021, are matched with CyGNSS specular points using the nearest neighbor method. Data division for training, testing, and validation follows a year-based approach. The CyGNSSnet architecture includes three main components: a map feature extractor using CNNs, an ancillary feature extractor, and a target regressor. Hyperparameters are fine-tuned to achieve optimal performance, with training conducted on HAICORE servers using PyTorch Lightning and an early-stop scheme to minimize training time.

To evaluate the model’s performance across diverse climates and land covers, the global map is stratified by intersecting land cover data from the Climate Change Initiative (CCI) with temperature regimes from the FAO's Global Agro-Ecological Zones (GAEZ v4). This stratification ensures a comprehensive assessment of CyGNSSnet's soil moisture estimation capabilities under varying environmental conditions. The study highlights the potential of advanced DL models like CyGNSSnet to address complex geospatial challenges, enabling more accurate and efficient global soil moisture retrieval.

References:

[1]           M. M. Nabi, V. Senyurek, A. C. Gurbuz, and M. Kurum, “Deep Learning-Based Soil Moisture Retrieval in CONUS Using CYGNSS Delay-Doppler Maps,” 2022, doi: 10.1109/JSTARS.2022.3196658.

[2]           T. M. Roberts, I. Colwell, C. Chew, S. Lowe, and R. Shah, “A Deep-Learning Approach to Soil Moisture Estimation with GNSS-R,” 2022, doi: 10.3390/RS14143299.

[3]           M. Asgarimehr, C. Arnold, T. Weigel, C. Ruf, and J. Wickert, “GNSS reflectometry global ocean wind speed using deep learning: Development and assessment of CyGNSSnet,” Remote Sens Environ, vol. 269, p. 112801, Feb. 2022, doi: 10.1016/J.RSE.2021.112801.

How to cite: Izadgoshasb, H., Xiao, T., Zhao, D., Pierdicca, N., Wickert, J., and Asgarimehr, M.: Adapting and Evaluating CyGNSSnet: A Deep Learning Approach to estimate Global Soil Moisture using GNSS Reflectometry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3607, https://doi.org/10.5194/egusphere-egu25-3607, 2025.

Abstract: The Earth is subject to complex internal and external forces in space. External forces include the gravitational attraction from the sun, moon, and other planets, and the internal forces include mass loads and frictional forces from the atmosphere, oceans, ice, snow, water, as well as interactions between the crust and mantle. Earth rotation parameters (ERPs) are essential for transforming between the celestial and terrestrial reference frames, and for high-precision space navigation and positioning. Amongst the ERPs, Polar Motion (PM) is a critical parameter for analyzing and understanding the dynamic interaction between the solid Earth, atmosphere, ocean, and other geophysical fluids. To investigate the impact of effective angular momentum (EAM) on long-term ERPs prediction, this thesis conducts research on long-term ERPs prediction considering EAM. Taking into account the influence of EAM, a discrete Liouville equation related to polar motion and UT1-UTC was first established, and the corresponding geodetic angular momentum was obtained. Finally, the residual geodetic angular momentum was obtained and modeled. Taking into account the residual of geodetic angular momentum and the experimental results of EAM, it is shown that, compared with Bulletin A, the LS+LSTM model has improved the accuracy of PMX, PMY, and UT1-UTC in the mid-and long term.

Keywords: Earth rotation parameters, Polar Motion, UT1-UTC, Least squares, Long Short-Term Memory model, effective angular momentum

Funding: Part of this work is supported by the National Natural Science Foundation of China (NSFC) (Grant No.42174037, No. 42030105, No. 42204006, No. 42274011, No. 42304095) and the State Key Laboratory of Geo-Information Engineering and Key Laboratory of Surveying and Mapping Science and Geospatial Information Technology of MNR, CASM (Grant No. 2024-01-01), the China Postdoctoral Science Foundation under Grant No.2024M752480.

How to cite: Wang, C., Wang, J., Zhang, C., Zhang, P., and Sang, J.: High-precision Earth Rotation Parameters Prediction with Physical Excitation Factors and Deep Learning Methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4895, https://doi.org/10.5194/egusphere-egu25-4895, 2025.

Slow slip events are typically associated with seismic activity, but the internal interactions and their relationship with earthquakes are still not well understood. With the rapid increase in Global Navigation Satellite System (GNSS) data, it has become possible to study the subtle slow slip signals in GNSS displacement time series using deep learning. In this study, GNSS displacement time series data from the Cascadia subduction zone are preprocessed using the Variational Bayesian Independent Component Analysis method to effectively remove non-slow-slip signals. Additionally, we developed a deep learning model that includes a multi-layer bidirectional Long Short-Term Memory  neural network and an attention mechanism, which can effectively detect slow slip events from complex data. Through this deep learning model, we successfully detected 56 slow slip events in the Cascadia region from 2012 to 2022. The start times, durations, spatial distribution, and propagation patterns of these 56 events were consistent with earthquake catalogs, providing new insights into the slow slip behavior of the Cascadia subduction zone. Overall, our work offers an effective framework for extracting subtle signals hidden in GNSS time series.

How to cite: Wang, J. and Chen, K.: Detecting slow slip events in the Cascadia subduction zone from GNSS time series using deep learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4976, https://doi.org/10.5194/egusphere-egu25-4976, 2025.

Global ionospheric maps (GIMs) are widely used ionospheric products, especially in Global Navigation Satellite System (GNSS) applications. They allow for instance to correct for the ionospheric delays in single-frequency applications. The input data for generating GIMs is typically obtained from dual-frequency observations at globally distributed GNSS stations. However, the distribution of these stations is in-homogeneous and predominantly concentrated in continental regions, resulting in large data gaps over the oceanic regions. The absence of data reduces the accuracy of GIMs in these regions. There exist other space techniques, such as satellite altimetry and GNSS radio occultation (GNSS-RO) that can retrieve the state of the ionosphere over ocean areas and have the potential to address such data gaps. However, the vertical total electron content (VTEC) observations from GNSS, satellite altimetry, and GNSS-RO differ due to variations in orbital altitudes and instrumental biases. Another challenge is the sparsity of observations from satellite altimetry and GNSS-RO, particularly when only considering data from a single day.

In this study, we developed a framework that integrates GNSS, Jason-3 satellite altimetry, and COSMIC-2 GNSS-RO observations in a GIM, based on a neural network (NN). First, we calibrated the satellite altimetry and GNSS-RO VTEC to be more consistent with GNSS VTEC. To address data sparsity, we used VTEC observations from satellite altimetry and GNSS-RO for the entire year 2023 to build a background ionospheric model with XGBoost. This background model captures the general climatological characteristics of the ionosphere over the oceans. We then utilized the background model to generate VTEC samples for training the NN-based GIM in regions lacking GNSS station observations. For our three test regions (Hawaii, Southern Atlantic, Antarctic), we find relative improvements in MAE of 37%, 11%, and 37% over the year 2023 compared to GNSS-only GIMs

The results demonstrate that the proposed data fusion method can effectively improve the modeling accuracy in regions with missing data.

How to cite: Iten, M., Mao, S., and Soja, B.: Ionospheric data fusion with GNSS, GNSS-RO and satellite altimetry based on machine learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5640, https://doi.org/10.5194/egusphere-egu25-5640, 2025.

Water vapor, the most significant greenhouse gas, plays a critical role in the Earth's climate system, influencing the hydrological cycle, energy distribution, and atmospheric dynamics. Integrated Water Vapor (IWV) serves as a vital parameter for understanding these processes. While traditional methods, including ground-based instruments and satellite observations, provide IWV measurements, they are often limited by spatial resolution, coverage, and accuracy. Advances in numerical weather models (NWM) and remote sensing have improved large-scale IWV estimations but still face challenges in capturing high accuracy. To address these limitations, this study introduces a novel approach using a Gaussian Mixed Long Short-Term Memory (GM-LSTM) deep learning model to generate high-resolution water vapor fields (WVF) with enhanced spatial and temporal resolution. The GM-LSTM integrates numerical weather models (NWM) and GNSS data to create an adaptive mapping for zenith wet delay (ZWD) estimation, which is then converted to IWV. By utilizing a bidirectional Long Short-Term Memory (Bi-LSTM) architecture and probabilistic density distribution sequences, the model not only improves ZWD estimation accuracy but also quantifies inherent uncertainties due to spatial heterogeneity. Compared with ERA5 and VMF3, the proposed GM-LSTM achieves an average RMSE reduction of 67.68% and 48.74%. The proposed WVF generation method was validated through an inter-comparison with MODIS and Fengyun satellite products, highlighting its superior accuracy and reliability. This study demonstrates the potential of deep learning models like GM-LSTM to overcome the limitations of traditional techniques, providing a transformative tool for high-resolution IWV estimation and supporting advancements in climate monitoring and weather prediction.

Keywords:

WVF, Inter-comparison, IWV, GM-LSTM, GNSS, MODIS, Fengyun satellite

How to cite: Wang, L., Wang, D., and Kutterer, H.: High-Resolution Water Vapor Field Generation Using the Gaussian Mixed Long Short-Term Memory Network: A Satellite-Based Inter-Comparison in Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6309, https://doi.org/10.5194/egusphere-egu25-6309, 2025.

Simulation studies are an essential tool in space geodesy. They support the optimization of ground and space networks, the exploration of innovative concepts, and the advancement of technological developments. Beyond measurement noise, realistic simulations must incorporate various error sources, including atmospheric effects, clock drift, and technology-related issues. For many space geodetic techniques, accurate simulations of tropospheric effects, particularly incorporating spatio-temporal correlations, are essential in this context. 

Traditionally, high-quality tropospheric simulations popular in the Very Long Baseline Interferometry (VLBI) technology rely on Kolmogorov turbulence theory combined with the frozen flow assumption. These simulations are parameterized using the refractive index structure constant (C_n), alongside auxiliary parameters like wind velocity and troposphere height. Although C_n values can be derived from Global Navigation Satellite System (GNSS) observations, most existing studies assume a generalized average troposphere, largely independent of specific locations or seasonal variations. Only a few incorporate location-based conditions, often through a simplistic latitude-based interpolation. Furthermore, reliance on GNSS data limits the ability to test potential network extensions when such observations are not available. 

This work enhances tropospheric simulations by introducing a global, three-dimensional (latitude, longitude, time) C_n model. The model is trained using zenith wet delay (ZWD) estimates from 21,000 globally distributed GNSS stations (2000–2023) and leverages meteorological data from the ERA5 reanalysis, including specific humidity across 11 pressure levels (1000 to 300 hPa) and wind velocity as features. Utilizing the XGBoost algorithm, the model supports short-term prediction scenarios with HRES weather forecasts and provides model uncertainty through an ensemble strategy. The proposed model is able to effectively capture the spatio-temporal patterns in the input data and provides high accuracy, allowing for enhanced simulations of space geodetic observations operating at radio frequencies such as VLBI and GNSS. Additionally, global monthly average estimates on a 0.25° x 0.25° latitude, longitude grid can be derived, offering a practical solution with sufficient accuracy for most simulation studies.

How to cite: Schartner, M.: A global refractive index structure constant model for enhanced tropospheric simulations of space geodetic observations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6936, https://doi.org/10.5194/egusphere-egu25-6936, 2025.

Detecting and analyzing spatiotemporal features of surface deformation signals caused by anthropogenic activities remains a challenging task in areas facing multi-hazard risks (e.g., earthquakes, subsidence, sea level rise, and flooding), particularly in coastal regions. We use Global Navigation Satellite System (GNSS) displacement time-series and apply deep learning procedures to identify and characterize ground deformation patterns resulting from natural subsidence and human activities. The focus area is Northern Italy, specifically the North Adriatic coasts, a region with many gas and oil production and storage operations. Unlike production sites, where hydrocarbons are extracted continuously throughout the year, storage sites follow a seasonal cycle: gas/oil is injected in summer and extracted in winter. Our goals are to (1) identify spatial and temporal ground deformation patterns in GNSS time series linked to these anthropogenic activities, and (2) estimate key reservoir properties such as volume, depth, and spatial extent. We generate synthetic training datasets using 114 GNSS stations and simulated reservoirs modeled with the Mogi model, varying depth and volume-change characteristics over time. Weighted Principal Component Analysis (WPCA) is employed to handle missing GNSS data by assigning zero weights to gaps. We will discuss results relative to the application of Convolutional Neural Networks, AutoEncoders, and Graph Neural Networks. After training and calibrating these models on synthetic GNSS datasets, we apply them to real-world GNSS observations. A comparison will be carried out, discussing pros and cons of the various techniques.

How to cite: Vu, D. T., Gualandi, A., Pintori, F., Serpelloni, E., and Pezzo, G.: Deep Learning for detecting anthropogenic ground deformation signals from GNSS time series along the North Adriatic coasts of Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7477, https://doi.org/10.5194/egusphere-egu25-7477, 2025.

Geodetic data analysis has traditionally relied on geophysical models and statistical methods to quantify Earth's deformation, correct for atmospheric effects, and refine measurement uncertainties. However, with the increasing volume and complexity of geodetic observations, machine learning (ML) may offer a better alternative for modelling non-linear motions of geodetic sites by capturing environmental effects and providing corrections for unmodelled influences.

ML has applications across various domains of geodesy, including coordinate time series analysis, geophysical deformation modelling, atmospheric and hydrological loading corrections, prediction of Earth orientation parameters, and tropospheric delay modelling. This study explores the use of ML techniques in geodetic data processing, focusing on modelling station height variations due to non-tidal loading (NTL) and other unmodelled effects in Very Long Baseline Interferometry (VLBI) data analysis using meteorological and land surface state variables.

Different ML approaches, including ensemble methods and neural networks, are examined to understand how well they can model displacement of geodetic sites due to meteorological and land surface state variables responsible for the redistribution of geophysical fluids on Earth. The study aims to compare these methods, highlighting their strengths and limitations in geodetic applications. By providing a broad perspective on ML integration in geodesy, this work contributes to the ongoing discussion on data-driven approaches for improving geodetic modelling and analysis.

How to cite: Singh, S., Böhm, J., Krásná, H., Böhm, S., Balasubramanian, N., and Dikshit, O.: Leveraging Machine Learning for Advanced Geodetic Data Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7827, https://doi.org/10.5194/egusphere-egu25-7827, 2025.

Regional sea level prediction plays a vital role in understanding the impacts of climate change and guiding the design of coastal infrastructure. Sea level rise is mainly driven by two primary factors: barystatic sea level change, caused by the melting of ice sheets, glaciers, and run-off of terrestrial water, and by steric sea level change, resulting from the expansion of seawater due to temperature and salinity changes. The former can be monitored from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On missions, and the latter is commonly calculated based on ocean salinity and temperature models. In this study, satellite altimetry was used to observe relative sea level changes spanning from May 2002 to April 2023. Specifically, barystatic sea level changes were derived using Mass Concentration (Mascon) solutions, while the steric height was estimated through the Ocean Physics Reanalysis model. According to the sea level budget equation, the total sea level change aligns closely with the combined contributions of barystatic and steric sea level components, validating the consistency of the data and methodology.

Machine learning has become increasingly significant in climate research in recent years. It enables the analysis of large and complex datasets that exceed human processing capabilities. Among the machine learning techniques, the Long Short-Term Memory (LSTM) model is particularly effective for the time series prediction due to its ability to capture long-term dependencies and patterns through its gated mechanisms. LSTM models excel at handling trends, seasonality, and noise in data, making them ideal for understanding the temporal dynamics of sea level changes and predicting future values.

In this research, we applied a CNN-LSTM model to predict total, barystatic, and steric sea level changes. The model leverages the feature extraction capabilities of convolutional neural networks (CNNs) combined with the sequential learning strengths of LSTM. The results of this study provide valuable insights into the contributions of mass and steric components to regional sea level changes. By predicting these signals, this research enhances our understanding of the mechanisms driving the sea level rise, offering the critical information for climate change mitigation and coastal adaptation planning.

How to cite: qiu, F., Gruber, T., and Pail, R.: Prediction of regional sea level change and its components using machine learning methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8792, https://doi.org/10.5194/egusphere-egu25-8792, 2025.

Big data is one of the most important phenomena of the 21st century, creating unique opportunities and challenges in its processing and interpretation. Machine learning (ML), a subset of artificial intelligence (AI), has become a foundation of data science, which enables applications ranging from computer vision, geoscience, aviation and medicine. ML becomes important when establishing mathematical models that connect explanatory variables to predicted variables is impossible due to complexity. Deep learning (DL), a subset of ML, has revolutionized fields such as speech recognition, email filtering, and time series analysis. However, DL methods face challenges such as high data demand, overfitting, and the “black box” problem.

We review least-squares-based deep learning (LSBDL), a framework that combines the interpretability of linear least squares (LS) theory with the flexibility and power of deep learning (DL). LS theory, widely used in engineering and geosciences, provides powerful tools for parameter estimation, quality control, and reliability through linear models. DL, on the other hand, deals with modelling complex nonlinear relationships where the mapping between explanatory and predicted variables is unknown. LSBDL bridges these approaches by formulating DL within the LS framework: training networks to establish a design matrix, an essential element of linear models. Through this integration, LSBDL enhances DL with transparency, statistical inference, and reliability. Gradient descent methods such as steepest descent and Gauss-Newton methods are used to construct an adaptive design matrix. By combining the transparency of LS theory with the data-driven adaptability of DL, LSBDL addresses challenges in different fields including geoscience, aviation, and data science. This approach not only improves the interpretability of DL models, but also extends the applicability of LS theory to nonlinear and complex systems, offering new opportunities for innovation and research.

By embedding statistical foundations in the DL workflow, LSBDL offers a three-fold advantage: i) Direct computation of covariance matrices for predicted outcomes allows for quantitative assessment of model uncertainty. ii) Well-established theories of hypothesis testing and outlier detection facilitate the identification of model misspecifications and outlying data, and iii) The covariance matrix of observations can be used to train networks with statistically correlated, inconsistent, or heterogeneous datasets. Incorporating least squares principles increases model explainability, a critical aspect of interpretable and explainable artificial intelligence, and bridges the gap between traditional statistical methods and modern DL techniques. For example, LSBDL can incorporate prior knowledge using soft and hard physics-based constraints, a technique known as physics-informed machine learning (PIML).

The approach is illustrated through three illustrative examples: Surface fitting, time series forecasting, and groundwater storage downscaling. Beyond these examples, LSBDL offers opportunities for various applications including geoscience, inverse problems, aviation, data assimilation, sensor fusion, and time series analysis.

How to cite: Amiri-Simkooei, A.: Theory and implementation of least-squares-based deep learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9878, https://doi.org/10.5194/egusphere-egu25-9878, 2025.

Sea level forecasting is crucial for safeguarding coastal regions, enhancing marine infrastructure, ensuring navigational safety, and mitigating natural hazards. Traditional methods, which often rely on single data sources like tide gauges or merged altimeters, may struggle to provide accurate predictions in highly dynamic regions due to their limited spatial and temporal resolution. Multi-Sensor Data Fusion has the potential to address these limitations by integrating data from multiple sensors, thereby improving the consistency, quality, and accuracy of predictions. While this approach has been successfully applied to other oceanographic parameters such as sea surface temperature (SST), sea ice, and salinity, sea level prediction remains challenging due to the spatial constraints of tide gauges and the relatively low temporal frequency of satellite observations. New satellite altimetry missions, such as the Surface Water and Ocean Topography (SWOT) mission, can deliver high-resolution data. When combined with deep learning (DL) techniques, this has the potential to improve the accuracy of sea level forecasting.

This research presents a novel DL approach for sea surface height (SSH) forecasting based on SWOT satellite data. By incorporating data from various sources (e.g. tide gauges, hydrodynamic models, and meteorological variables, such as wind speed and atmospheric pressure), the model aims to provide accurate, instantaneous SSH maps referenced to the geoid surface (i.e. Dynamic Topography (DT)). The DL architecture also encompasses attention mechanisms to prioritize spatially and temporally critical information, potentially overcoming the inefficiencies seen in traditional data assimilation methods.

The goal is to generate DT maps for real-time, adaptable predictions by integrating spatio-temporal data sources. Unlike previous methods, this approach incorporates instantaneous DT directly into the modeling process rather than solely for validation. The approach will be evaluated in the Baltic Sea to assess its precision. This model has the potential to set a new benchmark for sea level forecasting, offering valuable contributions to environmental monitoring, climate research, operational oceanography, and decision-making by providing high-resolution and interpretable predictions.

How to cite: Rajabi-Kiasari, S., Delpeche-Ellmann, N., and Ellmann, A.: Integrating Satellite Altimetry and Deep Learning for Enhanced Sea Level Forecasting , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9951, https://doi.org/10.5194/egusphere-egu25-9951, 2025.

Vegetation water content (VWC) is a critical parameter for understanding Earth’s ecological and hydrological systems, especially as climate change accelerates and extreme events become more frequent. Existing remote sensing methods for monitoring VWC face limitations due to restricted spatiotemporal coverage, soil moisture interference, and poor cloud penetration capability. To address these challenges, this study explores the synergy between unprecedentedly large datasets enabled by GNSS Reflectometry (GNSS-R) constellations and advanced deep learning algorithms for VWC estimation.

We propose a triple-collocated CGS dataset that integrates measurements from Cyclone GNSS (CYGNSS), Global Land Data Assimilation System (GLDAS), and Soil Moisture Active Passive (SMAP). Several deep learning models are benchmarked and evaluated over a three-year timespan. Validation results against ground truth measurements demonstrate robust performance with a minimum root mean square deviation (RMSD) of 1.099 kg/m². Moreover, predictive uncertainty is quantified using the Monte Carlo dropout method, providing a trustworthy representation for timely applications where ground truth data are unavailable.

Our study highlights the potential of combining GNSS-R with deep learning to address vegetation monitoring gaps. By leveraging the proposed CGS scheme and its large-scale dataset, we aim to catalyze further algorithmic advancements in GNSS-R-based vegetation monitoring and enhance the utility of GNSS-R for environmental applications.

How to cite: Zhao, D., Asgarimehr, M., Heidler, K., Wickert, J., Zhu, X. X., and Mou, L.: Advancing Global Vegetation Water Content Estimation with GNSS-R and Deep Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11214, https://doi.org/10.5194/egusphere-egu25-11214, 2025.

Radio Occultation (RO) using signals from Global Navigation Satellite Systems (GNSS) is one of the most promising remote sensing techniques for global atmospheric sounding. RO is a limb-sounding technique that uses GNSS signals, refracted during their propagation through the Earth’s atmosphere to a receiver on a low-Earth orbit (LEO) satellite. Over the last decades, RO products have been extensively used for data assimilation in Numerical Weather Prediction (NWP) as well as in climate science.

The RO retrieval of atmospheric profiles is based on accurately measuring phase deviations, which are induced by atmospheric bending of the signal. Over the past two decades, several improvements of the retrieval process have been achieved, but significant challenges remain, including the dependency of certain retrieval steps on external information or the assumption of spherical symmetry.

On the other hand, several RO missions such as the FORMOSAT-3/Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) and its successor COSMIC-2 have been initiated over the last two decades. In addition, several commercial companies have launched their own RO payloads, which led to an enormous increase in data amounts in recent years. These large data amounts make it suitable for the application of machine learning (ML) models, which have not been used much by the RO community until now. Only few studies have tested the suitability of ML for replacing classic retrieval algorithms and despite already achieving promising results, they were not able to uncover the full potential of ML, mostly due to the small amounts of data used.

This study presents an initial assessment of the performance of ML-based RO retrievals of temperature, pressure and humidity, trained using RO data from e.g. COSMIC-2 and state-of-the-art reanalysis products such as ERA5. It explores the suitability of various experimental setups and evaluates the sensitivity of the results to different feature setups.

How to cite: Aichinger-Rosenberger, M.: Machine learning-based retrieval of thermodynamic profiles from GNSS-RO observations: Preliminary results , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11342, https://doi.org/10.5194/egusphere-egu25-11342, 2025.

The detection and characterization of ground deformations play a critical role in understanding and mitigating the risks associated with natural hazards such as earthquakes, volcanic activity, and land subsidence. These deformations can have significant impacts on human life, infrastructure, and the environment, making their timely and accurate detection essential for disaster management and planning. Remote sensing technologies, particularly those that offer global coverage and high temporal resolution, are indispensable in capturing ground motion over large areas. 
Synthetic Aperture Radar (SAR) data, particularly from the Sentinel-1 mission, has revolutionized geodesy and remote sensing by providing high-resolution and frequent observations of Earth's surface. Interferometric SAR (InSAR) techniques allow for precise measurement of surface displacements at millimeter-scale accuracy, enabling the detection of subtle ground deformation patterns. Despite the availability of massive datasets from Sentinel-1, most of this data remains unlabeled, limiting the ability to directly apply supervised machine learning techniques for deformation classification. The need to manually label vast amounts of data is both time-consuming and resource-intensive, leaving a significant portion of the data underutilized for scientific discovery and practical applications.
Representation learning offers a promising approach to address these challenges by extracting meaningful features from large, unlabeled InSAR datasets. Self-supervised learning methods can leverage contrastive learning techniques to pretrain neural network encoders on deformation data, capturing patterns and structures inherent in the data without requiring labels. These learned representations can then be fine-tuned for downstream tasks, such as classifying deformation types (e.g., magma movements during volcanic eruptions or ground deformations coming from earthquakes) or detecting anomalies. By bridging the gap between vast, unlabeled data and the need for precise classification, representation learning enables more efficient use of InSAR datasets, advancing our ability to monitor and understand Earth's dynamic processes.

How to cite: Kaselimi, M. and Makantasis, K.: Learning InSAR Deformation Representations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12006, https://doi.org/10.5194/egusphere-egu25-12006, 2025.

Accurately monitoring and predicting the large-scale dynamic changes of water levels in coastal zones is essential for its protection, restoration and sustainable development. However, there has been a challenge for achieving this goal using a single radar altimeter and retracking technique due to the diversity and complexity of coastal waveforms. To solve this issue, we proposed an approach of estimating water level of the coastal zone in Beibu Gulf, China, by combination of waveform classifications and multiple sub-waveform retrackers. This paper stacked Random Forest (RF), XGBoost and CatBoost algorithms for building an ensemble learning (SEL) model to classify coastal waveforms, and further evaluated the performance of three retracking strategies in refining waveforms using Cryosat-2, SARAL, Sentinel-3 altimeters. We compared the estimation accuracy of the coastal water levels between the single altimeter and synergistic multi-altimeter, and combined Breaks for Additive Season and Trend (BFAST), Mann-Kendall mutation test (MK) with Long Short-Term Memory (LSTM) algorithms to track the historical change process of coastal water levels, and predict its future development trend. This paper found that: (1) The SEL algorithm achieved high-precision classification of different coastal waveforms with an average accuracy of 0.959, which outperformed three single machine learning algorithms. (2) Combination of Threshold Retracker and ALES+ Retracker (TR_ALES+) achieved the better retracking quality with an improvement of correlation coefficient (R, 0.089~0.475) and root mean square error (RMSE, 0.008∼ 0.029 m) when comparing to the Threshold Retracker & Primary Peak COG Retracker and Threshold Retracker & Primary Peak Threshold Retracker. (3) The coastal water levels of Cryosat-2, SARAL, Sentinel-3 and multi-altimeter were in good agreement (R>0.66, RMSE<0.135m) with Copernicus Climate Change Service (C3S) water level. (4) The coastal water levels of the Beibu Gulf displayed a slowly rising trend from 2011 to 2021 with an average annual growth rate of 8mm/a, its lowest water level focused on May-August, the peak of water level was in October-November, and the average annual growth rate of water level from 2022-2031 was about 0.6mm/a. These results can provide guidance for scientific monitoring and sustainable management of coastal zones.

How to cite: Qin, J., Li, Z., and Jiang, W.: Synergistic multi-altimeter for estimating water level in the coastal zone of Beibu Gulf using SEL, ALES + and BFAST algorithms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15082, https://doi.org/10.5194/egusphere-egu25-15082, 2025.

As a guiding mechanism for protecting cultivated land, achieving intensive and economical land use, and improving the ecological environment, the potential analysis of comprehensive land consolidation in the whole area relies on the accuracy of land use classification. In karst regions, such as the Li River Basin, the unique topography and geomorphology often render traditional land-cover classification methods prone to uncertainties, thereby affecting the consistency of conclusions in potential analysis for comprehensive land consolidation in the whole region. This study developed an improved random forest classification algorithm optimized for land-cover classification in the Li River Basin. Based on this algorithm, a potential evaluation model of comprehensive land consolidation in the whole area was constructed, and the spatial distribution characteristics of areas requiring consolidation under different potential levels for various land use types in the Li River Basin were analyzed in depth. The results indicate that the improved random forest algorithm performs best in land use classification in the Li River Basin, with overall accuracy and the kappa coefficient enhanced by 3% and 4%, respectively, compared with the standard random forest algorithm. The spatial distribution of potential levels of comprehensive land consolidation in the whole area across various land use types in the Li River Basin shows significant differences, ranking as ecological land > agricultural land > construction land. Compared to traditional evaluation models, the new model identifies consolidation areas for various land use types, covering 94.97% of the total area in the Li River Basin. This study can facilitate a comprehensive consolidation of land use types in karst regions from all elements, dimensions, and periods, thus provides scientific basis for land use and ecological protection in such areas. 

How to cite: Tang, Q., Jiang, W., and Li, Z.: Potential Analysis of the Comprehensive Land Consolidation for Entire Karst Region based on Improved Random Forest Method: A Case Study in the Li River Basin , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15130, https://doi.org/10.5194/egusphere-egu25-15130, 2025.

Accurate short-term prediction of Celestial Pole Offsets (CPO), essential for applications such as satellite navigation and space geodesy, remains a significant challenge. We addressed this task using a 1D Convolutional Neural Network (1D CNN), a machine learning model designed to capture temporal patterns effectively. Our objective was to enhance the prediction accuracy of the key CPO components, dX and dY. To improve model interpretability, we employed SHapley Additive exPlanations (SHAP), which identifies the most influential input features, such as historical dX and dY values and data from models like the Free Core Nutation (FCN) model. This transparency is critical for scientific and operational contexts.

We evaluated our model using various input data types, including rapid Earth Orientation Parameters (EOPs), Bulletin A data from the International Earth Rotation and Reference Systems Service (IERS), and FCN-derived data. Our results demonstrated improved prediction accuracy across all data sources, with rapid EOPs emerging as the most effective for short-term forecasts, particularly for the initial day. Leveraging rapid EOPs, we simulated the conditions of the 2nd Earth Orientation Prediction Comparison Campaign (EOPPCC) to further test our approach. The model outperformed other machine learning methods used in the campaign for dX predictions, although dY proved more challenging due to its complex dynamics.

This study highlights the potential of 1D CNNs in advancing CPO forecasting, particularly when coupled with interpretable frameworks like SHAP and diverse, high-quality data sources. Our findings underscore the transformative role of deep learning in enhancing the precision and reliability of Earth Orientation Parameter predictions, thereby supporting critical scientific and operational applications.

How to cite: Guessoum, S., Belda, S., Ferrándiz, J. M., Modiri, S., and Karbon, M.: DL for CPO feature selection and forecasting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16061, https://doi.org/10.5194/egusphere-egu25-16061, 2025.

Global Navigation Satellite System (GNSS) Ionospheric Seismology explores the ionospheric response to earthquakes and tsunamis, which generate Traveling Ionospheric Disturbances (TIDs) detectable through GNSS-derived Total Electron Content (TEC) observations. Real-time TID identification can offer a transformative approach to tsunami detection, enhancing tsunami early warning systems (TEWS) by extending coverage to open-ocean regions where traditional buoy-based systems are limited. Scalable and automated TID detection is therefore essential for augmenting TEWS capabilities.

In this work, we present a novel deep learning framework for real-time TID detection [3]. Leveraging Gramian Angular Difference Fields (GADFs), we transform TEC time-series data, retrieved via the VARION algorithm [1, 2], into images. Images were categorized based on ground truth: those overlapping labeled TID ranges were classified as TIDs, while others represented normal ionospheric TEC. This approach offers multiple advantages: (1) it preserves temporal dependencies through the sequential structure of GADFs, (2) allows reconstruction of original time-series data via its bijective nature, and (3) highlights temporal correlations within the data. Furthermore, GADFs encode temporal information directly in the images, making the method robust to missing data and suitable for image-based deep learning models in anomaly detection. Additionally, GADFs produce visually interpretable differences across classes, enhancing their utility.

We evaluated our framework using data from four tsunamigenic earthquakes in the Pacific Ocean: the 2010 Maule earthquake, the 2011 Tohoku earthquake, the 2012 Haida Gwaii earthquake, and the 2015 Illapel earthquake. The first three events were used for model training, while out-of-sample validation was performed on the Illapel earthquake to assess real-world applicability.

A single ResNet (50-layer) model was trained for TID detection, incorporating both anomalous (TID-containing) and normal data to ensure exposure to diverse scenarios. TEC data streams were processed chronologically in 60-minute windows, generating GADF images that the model classified as anomalous or normal. Predicted anomalies were concatenated into sequences and compared against ground truth. To further enhance performance, we integrated a false positive mitigation strategy, based on the likelihood of a TID at each time step, significantly reducing false positives. The model achieved an F1 score of 91.7% and a recall of 84.6%, demonstrating its strong potential for operational use in real-time applications.

By embedding deep learning into real-time GNSS-TEC analysis, this research represents a significant advancement in the use of TEC data for TEWS and underscores the potential of deep learning in geodetic time series analysis.

 References

[1] Savastano, G. et al. (2017). “Real-time detection of tsunami ionospheric disturbances with a stand-alone GNSS receiver: A preliminary feasibility demonstration”. Scientific reports, 7(1), 46607.

[2] Ravanelli, M., et al. "GNSS total variometric approach: first demonstration of a tool for real-time tsunami genesis estimation." Scientific reports 11.1 (2021): 3114.

[3] Ravanelli, M. et al. "Exploring AI progress in GNSS remote sensing: A deep learning based framework for real-time detection of earthquake and tsunami induced ionospheric perturbations." Radio Science 59.9 (2024): 1-18.

How to cite: Ravanelli, M., Constantinou, V., Liu, H., and Bortnik, J.: Harnessing AI in GNSS remote sensing: A Deep Learning framework for Real-Time Detection of Ionospheric Perturbations triggered by earthquakes and tsunamis , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16106, https://doi.org/10.5194/egusphere-egu25-16106, 2025.

Since 2002, the GRACE and GRACE Follow-On (GRACE/-FO) missions monitored total water storage changes (TWSC) – the amount of water stored on continents – with an unprecedented accuracy. However, there is a latency of a few months in generating the standard GRACE TWSC product while operational services that aim at such as forecasting drought or flood potentials require near-real time or even forecasted total water storage maps. In this study, we use machine learning to forecast the global GRACE-like total water storage change at long-lead times (up to one year ahead), where our approach works with lagged/forward-moving hydrometeorological variables/indices (e.g., precipitation) as predictors. We evaluate these data-driven TWSC forecasted from a hindcast experiment over 2010-2024 using GRACE observations and compare them to the existing model forecast products from the European Centre for Medium-Range Weather Forecasts (ECMWF)'s new long-range forecasting system (SEAS5). We find that the presented approach performs overall better than the land surface model (HTESSEL) as used by the ECMWF SEAS5 in forecasting TWSC. We forecast global TWSC at a grid resolution of 1° using three GRACE mascon solutions, resulting in three forecasted GRACE-like TWSC datasets. Possible applications include large-scale drought and flood early warning, constraining and downscaling water storage in hydrological forecasting models, the sea level forecasting, interpreting total water storage changes during the latency period of GRACE/-FO data, and geodetic applications like forecasting Earth orientation parameters via hydrological angular momentum excitation or forecasting loading corrections in GNSS and altimetry data analysis.

How to cite: Li, F. and Kusche, J.: Global long-lead forecast of total water storage and evaluation for 2010-2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19735, https://doi.org/10.5194/egusphere-egu25-19735, 2025.

Solar Radiation Pressure (SRP) plays a crucial role for Precise Orbit Determination of artificial satellites as it has been proven to be one of its major error sources. An essential parameter used for the calculation of SRP is the eclipse factor. To determine this factor along the orbit of the satellite, various shadow models have been implemented. The aim of this study is to investigate the differences the geometries of the models applied have, in different altitude orbits. To achieve this, we evaluate the results of shadow models used in the bibliography (ECSM, ESCM, Lunar shadow) along various Low Earth Orbits (LEO) and Medium Earth Orbits (MEO) satellites and demonstrate the effect of the geometries used in both cases. The study displays an overview of the results of each implementation and its computational complexity, as to provide an insight to researchers for which model to adopt when implementing an SRP model on LEO and MEO orbits.

How to cite: Krey, V., Papanikolaou, X., and Tsakiri, M.: An overview of shadow models implementations on LEO and MEO orbits., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-814, https://doi.org/10.5194/egusphere-egu25-814, 2025.

Solar Radiation Pressure (SRP), which plays a crucial role in satellite Precision Orbit Determination (POD), is associated with the satellite’s optical properties and surface structure. The BDS-3 satellites offer a wide range of featured services, which result in complex satellite structures. Significant systematic errors related to solar elevation angles (up to 30 cm) are observed in precision orbit products. To address this issue, we compared the theoretical trend and actual values of acceleration in the Sun-satellite direction, revealing that the satellite antennas may introduce additional SRP perturbations. Consequently, an a priori model that includes antenna illumination was established based on the adjustable box-wing model. The employment of the a priori model shows a notable enhancement in orbit accuracy for the BDS-3 satellites. The mean offset and standard deviation of SLR residuals for C45/C46 are reduced to a level consistent with satellites from the same manufacture. The systematic errors in the residuals are notably reduced, achieving the RMS of 3.85 cm, which represents a 74% improvement over the results obtained using only ECOM1. For IGSO satellites, the 3D OBD is reduced to 18.5 cm, reflecting improvements of 55% and 25% over ECOM1 and ECOM2, respectively. Moreover, the 3-day-arc POD has been demonstrated to markedly enhance the orbit internal consistency of the IGSO satellite, with a 3D OBD reduction to 3.1 cm.

How to cite: Geng, T., Zhang, C., and Xie, X.: Refinement of the solar radiation pressure model for the BDS-3 satellites with considering illuminated antennas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2005, https://doi.org/10.5194/egusphere-egu25-2005, 2025.

The Copernicus Precise Orbit Determination (CPOD) Service is key to the Copernicus Sentinel missions, supporting Sentinel-1, -2, -3, and -6 with critical orbit products and auxiliary data. These products facilitate the operational creation of scientific core outputs at ESA and EUMETSAT, accessible through the Copernicus Data Space Ecosystem (https://dataspace.copernicus.eu/).

Recent advances have pivoted towards the incorporation of new satellite units, notably Sentinel-1C and Sentinel-2C, launched in late 2024. These additions prompted thorough CalVal activities, ensuring the integrity and accuracy of Precise Orbit Determination. Initial solutions mirrored those of earlier Sentinel models, setting a standard baseline, while performing dedicated verification of Level-0 signal decoding.

A key enhancement is the integration of multiple PODRIX receivers in orbit, routinely tracking both GPS and Galileo signals together with Copernicus Sentinel-6A. GNSS antenna calibration has been pivotal, aiming to reduce multipath errors by creating a Phase Center Variation map. Cross-verification with solutions from the CPOD Quality Working Group (QWG), composed of renowned institutions such as AIUB, CNES, DLR, GFZ, JPL/NASA, PosiTim, TU Munich, and TU Delft, ensures these preliminary orbits meet Copernicus's precision demands.

Building on these innovations, the CPOD Service maintains its commitment to rapid, robust product delivery, achieving 3D RMS consistency below 1 cm with QWG's non-time-critical products and providing near-real-time solutions in under five minutes. Future efforts will focus on refining Sentinel-3's short-time critical products and advancing Sentinel-6 macro-models, as well as consolidating achievements related to the application of the ITRF20 Seasonal Geocenter Motion model.

This presentation will show results from recent satellite commissionings, and explore prospective enhancements within the CPOD service, showcasing the ongoing evolution in support of Copernicus missions' precision and operational efficiency. The contribution will also show the planned evolutions to continue improving and to pave the way for future Copernicus missions.

How to cite: Fernández Martín, C., Fernández Sánchez, J., Peter, H., Pinheiro, M., and Nogueira Loddo, C.: Copernicus POD Service: Status of Copernicus Sentinel Satellite Orbit Determination, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2256, https://doi.org/10.5194/egusphere-egu25-2256, 2025.

Since 2021, GMV has been developing FocusPOD, a new Precise Orbit Determination (POD) and Geodesy software package. Written in modern C++ and Python, FocusPOD is designed around four key pillars:
1.    Object-Oriented Programming: Utilizing C++17 and Python3, FocusPOD leverages external libraries and tools to minimize code development, focusing on specific algorithms. The C++ Standard Library (STL) efficiently handles large datasets.
2.    Data-Algorithm Separation: This approach allows data reuse for multiple purposes and consistent multi-technique processing with a single algorithm implementation.
3.    Data Model: Organizing data in a centralized model, akin to a relational database, facilitates easy navigation through extensive geodesy datasets.
4.    Multi-Use Case Support: FocusPOD supports various users, including experts, operators, and machine-to-machine architectures.

The first application of FocusPOD in 2023 was standalone GNSS POD. It is now operational in the Copernicus POD (CPOD) Service, generating millimeter-accuracy orbits for Copernicus Sentinel satellites. SLR processing was added to compute SLR residuals and biases for CPOD quality control with state-of-the-art accuracy. In July 2024, standalone DORIS POD was implemented, achieving centimeter-accuracy orbits for Sentinel-3 and -6 using DORIS only; same was demonstrated with standalone SLR POD. Future steps include integrating state-of-the-art tropospheric models for improving the accuracy of DORIS and SLR POD.

The latest incorporation into FocusPOD is the support to GNSS network processing, handling multiple receivers and GNSS constellations, to estimate orbits, clocks, station coordinates, troposphere, and Earth Orientation Parameters (EOPs). In parallel, advancement have been made to incorporate VLBI, implementing the IERS consensus model for observation reconstruction. These implementations will natively support single- and multi-technique at observation level with the four geodetic techniques. The final pending step is to estimate global solutions through Normal Equation (NEQ) stacking, on which the four techniques could be combined consistently.

This contribution will present the capabilities of FocusPOD, focusing on available models, algorithms, and the results achievable with each technique. It will also outline the current capabilities and maturity level of each technique, along with future development plans.

How to cite: Fernandez Sanchez, J., Fernandez Martin, C., Berzosa Molina, J., Bao Cheng, L., Muñoz de la Torre, M. A., Fernandez Uson, M., Lara Espinosa, S., Terradillos Estevez, E., and Ivanchuk, O.: FocusPOD: A POD and Geodesy SW Package, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2259, https://doi.org/10.5194/egusphere-egu25-2259, 2025.

Low Earth Orbit (LEO) satellites have nowadays shown great potential to enhance the existing GNSSs for better Positioning, Navigation, and Timing (PNT) services. Despite the requirements for high-accuracy real-time orbits, the distribution of various LEO satellite ephemeris is of concern, yet rarely studied for efficient broadcasting of the LEO satellite ephemeris. This is especially important for setting proper thresholds when broadcasting the LEO satellite ephemeris. In this study, the probability distribution of the LEO satellite ephemeris parameters is investigated together with the corresponding fitting accuracies. Twelve LEO satellites flying at different altitudes with different orbital characteristics are tested for 16-, 18-, 20-, and 22-parameter ephemeris fitting. The results reveal that an increase in orbital altitude does not only lead to improved fitting accuracy, but also results in a more concentrated distribution of orbital elements. Reducing the fitting interval and increasing the number of ephemeris parameters contribute positively to improving the fitting accuracy, where an accuracy of 1~2 cm or serval millimeters can be achieved with 10-min fitting interval and 20/22-parameter ephemeris for a 300~1400 km orbital altitude. This, however, comes at the cost of dispersed distribution of the orbital elements, i.e., with wider ephemeris threshold required. It was also found that the mean values of certain crucial ephemeris parameters, e.g., the mean motion correction, the right ascension of ascending node rate, and the second-order harmonic coefficients Cus2 and Crc2, are highly correlated with the orbital altitudes and inclinations.

How to cite: Wei, C. and Wang, K.: Characteristics of Probability Distribution and Fitting Accuracy for LEO Satellite Ephemeris, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3491, https://doi.org/10.5194/egusphere-egu25-3491, 2025.

Real-time data processing onboard is increasingly essential for future Low Earth Orbit (LEO) satellites. We propose an ultra-rapid onboard orbit determination (OD) strategy that achieves decimeter-level accuracy, potentially up to centimeter-level. This approach enables high-precision OD and prediction using either precise GNSS products from ground stations or broadcast ephemeris. Consequently, it allows satellite payloads to deliver real-time, high-performance services to ground users, with significant potential for various applications. Experimental results show that using IGS final GNSS products, this method achieves 5 cm accuracy for OD and better than 10 cm for 10-min orbit prediction. With broadcast ephemeris, the accuracies are better than 45 cm for OD and 1 m for 10-min orbit prediction.

How to cite: Luo, P. and Song, Y.: An Onboard Ultra-Rapid Orbit Determination Strategy for LEO Satellite Utilizing GNSS Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5062, https://doi.org/10.5194/egusphere-egu25-5062, 2025.

The NASA-CNES climate science Surface Water and Ocean Topography (SWOT) satellite was successfully launched in December 2022. This mission embodies the longstanding cooperation between CNES and NASA Jet Propulsion Laboratory in space oceanography for 40 years, initiated with TOPEXPoseidon in 1992, subsequently pursued through the Jason series of satellites (1 to 3 between 2001 and 2016) and continued in 2020 with the Copernicus Sentinel-6 mission.

SWOT is the first space mission that will study nearly all of the water on the Earth’s surface. To complete this global survey and mapping of the finer details of the ocean’s surface topography and water bodies over time, the satellite is equipped with a GPS (Global Positioning System) and DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) dual-frequency receivers, as well as a Laser Retroreflector Array (LRA) to support verification of the challenging Precision Orbit Determination (POD) requirements

In this poster, we will present the current results and efforts underway to improve the modeling of Solar Radiation Pressure (SRP). Residual signatures of systematic errors related to the Sun’s elevation angle are observed in-flight when using the current a priori SRP model. To address this issue, we analyze once-per-revolution empirical along-track and cross-track accelerations with respect to the beta prime angle, aiming at reducing this dependency. An updated box-wing model is thus derived for SWOT moving from pre-launch to adjusted data (geometry, surface properties).

How to cite: Blondel, S., Couhert, A., Moyard, J., Mercier, F., and Houry, S.: Refinement of the solar radiation pressure model for the SWOT satellite , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8080, https://doi.org/10.5194/egusphere-egu25-8080, 2025.

A significant contributing error source in the computation of the ITRF is the estimation of terrestrial ties, between geodetic reference points at colocation sites. The discrepancy in the description of the vectors, as determined through space geodetic observations and terrestrial surveying techniques, can be as much as 10 cm at certain sites.

In response, in 2022, the European Space Agency proposed the GENESIS satellite mission which is a specially designed geodetic satellite equipped with the four space geodetic techniques i.e., LRA, GNSS, DORIS and VLBI to achieve an ITRF with a positional accuracy of one mm and a stability of 0.1 mm/year.

Given the increase in the number of LEO satellites that are equipped with multiple geodetic techniques, it is opportune to assess and develop the capability of co-location in space (at the satellite) to achieve these accurate terrestrial ties at sites that are collocated with multiple space geodetic observing techniques.

The aim of the of the study is to determine the feasibility of colocation in space by undertaking multi-technique orbit determination, estimating station coordinates and hence the terrestrial ties between collocated observing techniques using multi-technique data from the Sentinel satellites. This may inform the GENESIS geodetic mission.

Our project estimates orbits for the available techniques on the respective satellites, from 2016 to 2022.  The observation network and its categorisation based on collocated systems, the computations standards implemented for each observation type and the subsequent combination method to determine the coordinates for each technique at each site is presented. 

The vectors as determined between adjusted station co-ordinates are compared to the official terrestrial ties. This measure may provide insight into the stacking and combining of POD solutions; and station position estimates that may be performed for optimum space co-location results and identify any limitations or potential improvements in the processing strategy. 

How to cite: Desai, A., Combrinck, L., and Govind, R.: Precise Multi-Technique Orbit Determination of the Sentinel Satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9284, https://doi.org/10.5194/egusphere-egu25-9284, 2025.

Satellite Laser Ranging (SLR) has become an invaluable core technique in numerous geodetic applications. SLR measurements to passive spherical satellites essentially contribute to the determination of geocenter coordinates and global scale in the International Terrestrial Reference Frame (ITRF) realizations. In addition, SLR measurements to active satellites in Low Earth Orbit (LEO) are up to now mostly used for independent validation of orbit solutions, usually derived by microwave tracking techniques based on Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) or Global Navigation Satellite Systems (GNSS). This allows for the analysis of systematic orbit errors (e.g., originating from poorly known non-gravitational perturbations or sensor offsets) not only in the radial direction (key to satellite altimetry missions), but in three dimensions.

It has recently been shown, in Saquet et al. (2023), that the analysis of SLR data to a constellation of active LEO satellites with fixed microwave-derived orbit solutions is a promising approach to exhibit SLR range biases independently from well-known correlation issues and less prone to geographically correlated orbit errors. Clearing systematic range biases from SLR observations is also an essential step to meeting stringent future requirements such as for ESA’s GENESIS mission or enabling the calibration of altimeter range biases for the next generation of altimetry missions.

In this paper, we use geodetic sphere (e.g., LAGEOS-1/2) measurement SLR residuals to assess the quality of the station range biases derived from satellite altimetry compared to ILRS-based range bias values. Systematic differences between the two independent approaches are analyzed, especially for well-performing laser stations with diverse detector types (e.g., single/multi-photon). Finally, relying on multiple years of observations, the contribution of tropospheric delay modeling errors to these biases is estimated.

How to cite: Saquet, E., Couhert, A., Reinquin, F., and Banos Garcia, A.: Clearing systematic range biases from SLR observations: assessment and outlook, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10499, https://doi.org/10.5194/egusphere-egu25-10499, 2025.

The Sentinel-6A satellite, launched on November 21, 2020, is equipped with a dual-constellation (Galileo and GPS) onboard receiver for precise orbit determination (POD). Since launch, there have been significant improvements in the force models and data processing strategies. This has resulted in significant improvements to orbit accuracy. The Gravity Recovery and Climate Experiment-Continuity (GRACE-C) mission, which will be launched in 2028, will carry on a similar onboard receiver to Sentinel-6A. The main purposes of this study are to extend our software to process both Galileo and GPS data for preparing GRACE-C and to investigate how well the orbits of the Sentinal-6A satellite can be currently determined using Galileo or/and GPS data based on the current models and approaches. In this study, we present the results of Sentinel-6a POD solutions. The orbit accuracy is assessed using several tests, which include analysis of orbit fits, Satellite Laser Ranging (SLR) residuals, internal and external orbit comparisons. We show that less than one-cm radial orbit accuracy for the Sentinel-6A satellite has likely been achieved through different orbit accuracy evaluations. The precise Sentonel-6A orbits determined based on Galileo and GPS observations can meet the stringent requirement on radial orbit accuracy (1.5 cm).

How to cite: Kang, Z., Nagel, P., Save, H., Bettadpur, S., and Pie, N.: Precise Orbit Determination for Sentinel-6A using Galileo and GPS observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13160, https://doi.org/10.5194/egusphere-egu25-13160, 2025.

Due to mission objective constraints, some low Earth orbit satellites are required to operate in flexible attitude modes, but meanwhile stable Precise Orbit Determination (POD) performances must be guaranteed persistently. In this case, a single zenith-mounting antenna, as most missions have done in the past, will not fulfill POD requirements because its GNSS signal tracking might be significantly downgraded in certain attitude modes. A straightforward solution is carrying two antennas for better receiving geometry. This research investigated PODs for different satellites using GNSS observations from two antennas, which were installed with an angle varying between 45 and 180 degrees in the satellite body-fixed reference frame. The preprocessing and screening of GNSS observations was elaborately done to maximize the continuous arc for ambiguity estimation, in particular for cases when the two antennas tracked the same GNSS satellites alternatively or simultaneously. The potential signal delay between the two antennas and the independent phase patterns need to be evaluated. Afterwards the different GNSS observations were robustly merged referring to the satellite’s center-of-mass. Results indicated that the GNSS observation fusion strategy significantly enhanced the stable POD performances for attitude modes where single antenna was impossible to receive sufficient GNSS observations. The overlapping consistency and internal consistency between the reduced-dynamic orbits and the kinematic orbits were only 1-2 cm in the local orbital reference frame, obtaining a similar level as other renown missions with single zenith-mounting antenna. Besides, such dual-antenna GNSS tracking configuration enabled potential assessments of center-of-mass coordinates as well as other applications.

How to cite: Mao, X., Wang, W., and Gao, Y.: Precise orbit determination for satellites in flexible attitude modes using dual-antenna GNSS observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14826, https://doi.org/10.5194/egusphere-egu25-14826, 2025.

The atmospheric delay correction of Satellite Laser Ranging (SLR) ground observations depends on the state of the neutral atmosphere. In the state-of-the-art SLR network processing, this delay is an empirical function of local station-based meteorological variables. We propose an alternative modelling approach commonly used in Global Navigation Satellite Systems (GNSS). Here, the slant delay (SD) is estimated via ray tracing (RT) with atmospheric information provided by Numerical Weather Prediction (NWP). We compare the default processing of the atmospheric correction using the Mendes-Pavlis (M-P) model supplied with station meteorological data and the alternative processing using the Least Travel Time version 2 (LTT v2) ray tracer coupled with the Open Integrated Forecasting System (OpenIFS) NWP model of European Centre for Medium-Range Weather Forecasts (ECMWF). Additionally, we employ a hybrid approach where the M-P model is supplied with interpolated weather forecast data. Our SLR processing setup is a position determination of 10 satellites using only the SLR observations from December 2016, done using the Gravity Recovery Object Oriented Programming System (GROOPS) toolkit. We compare three atmospheric modelling approaches by employing their slant delay estimates in the SLR processing and performing residual analysis.

How to cite: Vasiuta, M., Süsser-Rechberger, B., Mayer-Guerr, T., and Järvinen, H.: Employing the numerical weather prediction for direct modelling of SLR atmospheric corrections, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15720, https://doi.org/10.5194/egusphere-egu25-15720, 2025.

ESA’s Genesis mission, planned to launch in 2028, aims to contribute to a highly improved International Terrestrial Reference Frame (ITRF) with an accuracy of 1 mm and a stability of 0.1 mm/year. It will combine GNSS, DORIS, SLR and VLBI space geodetic techniques, acting as the first ever space-tie using these four techniques. The satellite will orbit at an altitude of 6000 km and will be equipped with two GNSS antennas, pointing in zenith and nadir direction, in order to counteract the loss of GNSS coverage at those altitudes.

For the mission to provide a strong contribution to the ITRF, dynamic satellite orbit modeling needs to be done as empirical orbit parameters are closely correlated with some geodetic parameters. Thus, the geometry and optical properties of the satellite, expressed as a macro model, should be described as accurately as possible.

During the development of Genesis, different spacecraft designs were considered. We focus on the original box-wing model, consisting of a cuboid body and a single solar panel, and the newer model, which is similar to Sentinel-6. Their respective influence is determined for a Genesis-only precise orbit determination as well as a global combined solution, where the Genesis orbit, GNSS orbits and clocks, ground station coordinates and geodetic parameters are estimated together. In addition, uncertainties to the optical properties of single or multiple surfaces of the spacecraft were introduced in order to test how macro model errors propagate into the global combined solution.

Using simulated pseudo-range and carrier phase GNSS data for Genesis and the ground stations, we reconstruct the orbit and geodetic parameters. A comparison of the solutions to the simulation truth allows for a direct quantification of the impact of different macro models and possible errors.

How to cite: Miller, A., Arnold, D., Jäggi, A., Steigenberger, P., and Montenbruck, O.: The influence of non-gravitational force modeling on Genesis and GNSS orbit and geodetic parameter estimations using two different macro models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16573, https://doi.org/10.5194/egusphere-egu25-16573, 2025.

With the widespread application of precise point positioning (PPP), real-time clock offset products have become a focal point of global navigation satellite system (GNSS). Real-time clock offset estimation offers high accuracy but demands stable data communication and involves significant computational pressure. And the accuracy of ultra-rapid products does not meet the requirements of positioning, navigation and timing (PNT) services. To address this, a short-term clock prediction method based on low sampling rate estimation is proposed. This method provides users with a set of clock model coefficients, enabling them to obtain high sampling rate clock offset at any time. Based on the clock products with 60s intervals estimated by square root information filtering (SRIF) from 80 stations, the most suitable short-term model that the linear model with the same arc length for fitting and prediction is determined by adaptive analysis of the order of polynomial model and data arc lengths. Based on this, short-term predicted parameters for 5min, 10min, 15min, 30min and 60min are obtained. These parameters are then interpolated to 30s interval for detailed accuracy assessment and PPP validation. The results indicate that the clock offset predicting accuracies of BDS-3 are 0.029ns, 0.033ns, 0.037ns, 0.047ns, 0.071ns for 5min, 10min, 15min, 30min and 60min, while the Galileo are 0.023ns, 0.027ns, 0.032ns, 0.039ns, 0.062ns. The predicted clock offsets of Galileo are slightly better than those of BDS-3. The PPP results show that the 2D and 3D positioning accuracies for the 5min prediction are 0.058m and 0.115m, respectively, with positioning accuracy declining as the prediction arc length increases. Overall, the positioning performance of the predicted clock products within 30min are nearly consistent to the real-time estimated clock. Compared to Centre National d’Etudes Spatiales (CNES), the results of PPP performance are similar，and superior to the performance of ultra-rapid clock products. Therefore, short-term predicted products based on low sampling rate estimated clock can serve as a more stable alternative to real-time products in the PPP applications. The updating frequency of the clock offset model coefficients is determined based on the needs of PPP users. The method reduces the sampling rate for estimating clock offset while maintaining high-precision clock offset products. Additionally, it can still offer high-precision real-time clock offset prior information to the PPP users during interruptions in real-time estimation.

How to cite: Cao, Y., Huang, G., Qin, Z., Xie, S., Xie, W., Fan, Y., and Du, S.: Short-Term Clock offset Predicting Products Based on Low Sampling Estimation for Real-time Service, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16653, https://doi.org/10.5194/egusphere-egu25-16653, 2025.

For the past fifty years, geodetic satellites have contributed to improve our knowledge on various Earth's physical behaviors. The purpose of this paper is to reassess the value of the geocentric gravitational constant (GM), defined by the product of the Earth's universal gravitational constant G and its mass M, from Satellite Laser Ranging (SLR) observations. Indeed, its relatively large uncertainty of 2.0 ppb (Ries et al., 1992) is not compatible with the final goal of the GENESIS MEO (Medium Earth Orbit) mission to realize the Terrestrial Reference Frame with an accuracy of 1 mm. The core of this analysis is based on the simultaneous estimation of the Earth's GM with laser station and satellite biases, taking the most of historical passive geodetic satellites, including three pairs of "twin" satellites to validate independently the accuracy of the newly derived GM value. Furthermore, by combining MEO and LEO (Low Earth Orbit) satellites, a consistent value of GM has been reassessed, this value being higher and less uncertain than the currently used reference value determined in 1992. In particular, the influence of errors in the modeling of the Earth radiation pressure and station coordinates on GM was evaluated.

How to cite: Cherrier, M., Couhert, A., Exertier, P., Mercier, F., and Saquet, E.: Reducing uncertainties in the determination of the Earth's GM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17971, https://doi.org/10.5194/egusphere-egu25-17971, 2025.

Precise Orbit Determination (POD) of Global Navigation Satellite Systems (GNSS) satellites relies on precise satellite attitude data to accurately model satellite dynamics and observation geometry. Errors in the attitude control, such as biases, and periodic signals, have the potential to propagate into orbit estimates and derived geodetic parameters, thereby influencing the accuracy required for high-precision geodetic applications. Furthermore, accurate attitude determination plays a critical role in Next-Generation GNSS, particularly for the implementation of inter-satellite range links. This study presents a simulation framework to analyse the impact of such effects on GNSS attitude data and their implications for POD.

A Galileo-like constellation is simulated over a three-year period, employing state-of-the-art methods and datasets, including ITRF2020. The basis of the simulation are realistic assumptions concerning satellite geometry and attitude control. Systematic orientation biases and periodic signals, such as misalignments in solar panel orientation or inaccuracies in yaw steering, are applied to the attitude data to emulate potential errors in real systems. The simulation then examines the propagation of these errors into POD solutions, including their effects on orbit errors and clock estimates.

Particular attention is given to systematic effects arising from solar radiation pressure (SRP) modelling in combination with systematic attitude errors. The results obtained demonstrate the sensitivity of GNSS POD to precise attitude knowledge, thereby providing valuable insights for the design and calibration of future GNSS. This study emphasises the critical role of attitude control in achieving the accuracy objectives outlined by the Global Geodetic Observing System (GGOS) for subsequent reference frame determination.

How to cite: Schreiner, P., Glaser, S., König, R., Neumayer, K. H., Raut, S., and Schuh, H.: On the Impact of Attitude Data Deviations for GNSS Precise Orbit Determination, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18031, https://doi.org/10.5194/egusphere-egu25-18031, 2025.

We have developed three innovative, empirically-derived all-force radiation pressure models for multi-GNSS, addressing the shortcomings of traditional models that rely on simplified spacecraft geometries and extensive metadata. The models were created using ESA and CODE orbit products with different arc lengths (5-day and 10-day). This presentation will share the findings of a comparative study of these three models, based on a full year of high-precision GNSS data processing.

The results reveal significant variations in model performance across different GNSS constellations. A 5-day ESA-based model with a comprehensive parameter set (including a Z0 term and a Galileo-specific term) showed superior performance for Galileo and GPS. In contrast, a 5-day CODE-based model performed best for BeiDou, underscoring the importance of data source quality. Interestingly, a 10-day ESA-based model demonstrated lower performance, suggesting that longer arcs do not necessarily enhance model accuracy.

Further analysis indicated that while the models effectively reduced the variability in estimated ECOM parameters, consistent non-zero mean values for some parameters—particularly for BeiDou—highlight the presence of unmodeled forces. This is further supported by the anomalous behavior of certain BeiDou satellites, emphasizing the need for dedicated modeling strategies tailored to specific constellations.

This work underscores the critical role of data source quality, arc length selection, and careful parameterization in developing accurate and reliable all-force radiation pressure models for multi-GNSS. To further enhance the models, we will investigate these factors in greater detail, explore alternative parameterizations, and develop strategies to improve performance for challenging constellations, especially BeiDou.

The models developed in this study are freely available to the scientific community to support further research and enhance the accuracy of GNSS precise orbit determination.

How to cite: Springer, T. and Dilssner, F.: Taming the Invisible: A Comparative Study of All-Force Radiation Pressure Models for Multi-GNSS, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19120, https://doi.org/10.5194/egusphere-egu25-19120, 2025.

Genesis is ESA's future mission that will contribute to a highly improved Earth reference frame with a target accuracy of 1 mm and a long-term stability of 0.1 mm/year, providing a coordinate system for the most demanding scientific applications on our planet.

The baseline for the Genesis satellite is to combine all four major space-geodetic techniques: Very-Long-Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS) and Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS). The synchronisation and cross-calibration of these instruments are key to determine the inherent biases of each technique, allowing for a coherent combination of the relevant observations resulting in an improved accuracy of the orbit determination.

In preparation for this mission, which is expected to be launched in 2028, the Navigation Support Office of the European Space Agency will be responsible for the Precise Orbit Determination (POD) of the GNSS satellites and for the Genesis satellite. Hence, the Office is already preparing the tools to be ready for the processing of all the observables coming from these four techniques in a combined and coherent manner.

Real data obtained from ESA’s missions, including the Copernicus Sentinel missions, will serve as the basis for testing, validating, and further developing and enhancing the capabilities of a multi-technique processing, including GNSS, SLR and DORIS. In parallel, the Office is preparing to process the first high precision VLBI observations from a satellite.

A detailed description of the POD methodology that the Navigation Support Office intends to apply for Genesis mission as well as the first results will be presented and discussed at the EGU General Assembly.

How to cite: Berton, J.-C., Bruni, S., Dilssner, F., Otten, M., Sermanoukian Molina, I., Springer, T., van Kints, M., Fusco, G., Gidlund, S., Gini, F., Schoenemann, E., Sakalauskaite, E., Waller, P., and Enderle, W.: A new combined processing for Genesis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20067, https://doi.org/10.5194/egusphere-egu25-20067, 2025.

The quality of low Earth orbit (LEO) satellite-borne global positioning system (GPS) observation data has an important influence on the precise orbit determination of LEO satellite and the study of the ionosphere. In this contribution, we develop a geometry-free orbit-dynamic-constraint approach to analyze the satellite-borne GPS observations errors, including code errors, carrier phase errors, receiver clock errors, ionospheric delay, to detect and repair cycle slips for satellite-borne dual-frequency carrier phase observations. Different from the traditional methods suitable to satellite-borne GPS observations, we take full advantage of the correlations between the dual-frequency observations, between the satellite orbit variations and the orbit dynamic background models, without a prior precise orbit. The proposed approach can not only remove the geometry variations between GPS satellites and LEO satellite, but also have partial characteristics of other signals separated from GPS observations, such as the receiver clock offset. Then, the performance of the proposed approach is verified by GPS measurement data of GOCE/GRACE satellite with different sampling interval. The results indicate that the proposed approach preforms well on observations error analysis, can effectively detect and fix cycle slips with high success rates, even in real-time applications.

How to cite: Zhu, H., Zou, X., and Wei, H.: Geometry-free error analysis and cycle slips detectionof GPS observations on the basis of dynamic information and its applications on LEO precise orbit determination, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21056, https://doi.org/10.5194/egusphere-egu25-21056, 2025.

How to cite: Dunn, P., Husson, V., and Szwec, C.: Long Term Stability of the SLR and VLBI Geodetic Networks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1597, https://doi.org/10.5194/egusphere-egu25-1597, 2025.

This effort as part of the research unit "Clock Metrology" funded by the German Research Foundation (DFG) focuses on innovative strategies for combining all four space geodetic techniques—DORIS, GNSS, SLR, and VLBI—to significantly enhance the global Terrestrial Reference Frames (TRF) with the goal to achieve the GGOS (Global Geodetic Observing System) requirements of 1 mm accuracy and long-term stability of 1 mm/decade. To achieve this goal, a novel approach of combining the space geodetic techniques is being developed. A common target (CT) will be introduced at the Geodetic Observatory Wettzell (GOW) to combine all the techniques at a common reference point. Additionally, a common clock (CC) will be established at GOW to reference the observations of all techniques to a single time frame. The impact of the CT and CC on the TRF combination is evaluated through simulations involving all four space geodetic techniques. In this study, we exhibit the results of the SLR, GNSS, and VLBI simulations of global station networks as reference solutions for the following implementation of CT and CC. As basis for these simulations, we used current state-of-the-art models and standards based on real observation data to determine realistic accuracy measures for today’s technique-specific observations. We assume a white noise of the observations with an amplitude corresponding to the noise derived from actual data analysis of the real observations for each technique. Subsequently, weekly normal equation systems from the simulated data were accumulated into a combined global TRF solution over a 7-year period to assess the impact on the derived station coordinates and velocities, as well as the Earth Rotation Parameters. The estimated corrections to the station positions remain within a few millimeters, indicating a consistent solution w.r.t a priori. Additionally, in order to perform the combination via a CC, extended software modifications are carried out as in the space geodetic data analysis the clock parameters are usually pre-eliminated and no longer available for further processing. Based on these modifications, first results of the novel combination of intra- and inter-techniques at GOW will be presented.

How to cite: Reinhold, A., Glaser, S., and Seitz, M.: On simulation studies for novel combination strategies of space geodetic techniques, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1646, https://doi.org/10.5194/egusphere-egu25-1646, 2025.

Estimation of Euler pole parameters (EPPs) is a critical step in developing NATRF2022, the upcoming realization of the North American (NA) terrestrial reference frame. These parameters characterize the tectonic motion of the NA plate relative to the ITRF2020/IGS20 reference frame. Improving the accuracy of EPPs reduces residual velocities within the plate, which in turn enhances the stability of geodetic coordinates and extends the validity period of the reference frame. The growing network of consistent, long-term continuously operating GNSS stations provides a robust and reliable source of velocity data for estimating EPPs. Currently, two methods are used for estimating EPPs: (1) solving the classic Euler’s pole theorem in inverse mode, based on the rigid plate assumption, and (2) modeling the deformation field of the tectonic plate to estimate parameters describing the net rotation of the deforming plate, consistent with the deforming plate hypothesis. Both methods are sensitive to the selection of GNSS stations, resulting in slight variations in the estimated EPPs. This sensitivity is further compounded for the NA tectonic plate due to the presence of non-secular and non-stationary deformation induced by glacial isostatic adjustment (GIA) across the plate, as well as the complex dynamics of the diffused boundary zone along its western margin. To address these challenges, a statistical algorithm based on the Maximum Likelihood Estimation (MLE) theory is proposed, offering unbiased parameter estimation for sufficiently large samples. The methodology begins with the selection of stations featuring stable monuments with at least three years of continuous time series. An adaptive grid comprising 50 to 100 cells is considered to ensure a homogeneous spatial distribution of the selected stations. Within each grid cell, one station is randomly selected with place back, and the EPPs are estimated using station velocities. This procedure is repeated many times following the Monte Carlo method to generate a large set of EPP estimates. Histograms of the estimated parameters are then formed to identify the underlying statistical distribution of the EPPs. Finally, the best values corresponding to the maximum likelihood probabilities are selected as the optimized EPPs. The resulting EPPs are then compared with those reported in previous studies, and the significance of the observed differences is evaluated in detail.

How to cite: Goudarzi, M. A.: Statistical determination and analysis of the Euler pole parameters for NATRF2022, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1655, https://doi.org/10.5194/egusphere-egu25-1655, 2025.

Global Navigation Satellite Systems (GNSS) are based on measurements of signal propagation time, so that clock information is required for both the transmitting satellite and the receiving ground station. In undifferenced GNSS network analyses, synchronization errors of the satellite and station clocks are usually estimated by epoch-wise biases. If, as is common in practice, white noise is assumed as stochastic behavior for the clocks, there are high correlations between the clock estimates and other geodetic parameters. While the satellite clock is correlated with the radial orbit component and geocenter parameters, the station clock shows high correlations with the station height coordinate and the tropospheric zenith delay. These effects can be reduced by introducing proper models for describing the clock characteristics. Especially for global network solutions, deterministic clock modeling is suitable to reduce a substantial number of clock estimates. However, adequate modeling requires a high degree of stability for the corresponding clocks.

In this contribution, we show preliminary results of modeling highly stable GNSS ground and space clocks using piece-wise linear representations. For the satellites, we select the rubidium clocks of the GPS IIF and IIIA blocks as well as the passive hydrogen maser clocks of the Galileo FOC spacecraft for modeling. In addition, a selection of hydrogen maser stations of the International GNSS Service (IGS) is also modeled. Over a period of several weeks, daily network solutions with and without piece-wise linear clock modeling are processed and then compared. We discuss different strategies and show the effects of various modeling options (length of split interval, parameter weighting) on the correlations of the estimated parameters.

How to cite: Widczisk, J. S., Männel, B., and Wickert, J.: Modeling of highly stable GNSS ground and space clocks using piece-wise linear representations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2545, https://doi.org/10.5194/egusphere-egu25-2545, 2025.

To update the ITRS 2020 realizations which are based on observations from the geodetic space techniques VLBI, SLR, GNSS and DORIS until the end of 2020, the ITRS Product Center asked the Technique Centers (TCs) for an extension of these series by as consistent as possible operational series. However, the GNSS input series which formerly realized an own GNSS scale, the full history of data was recomputed by the IGS TC by adopting the ITRF2020 scale based on the VLBI and SLR scale contributions.

DTRF2020, calculated by DGFI-TUM, realizes the scale from VLBI and GNSS contributions and thus needs for its update IGS/GNSS series realizing the GNSS scale. Therefore, the IGS TC provided, in addition, an extension series consistent to the input series for the ITRS 2020 realization. Moreover, the GGFC provided extensions of the previous non-tidal loading (NTL) displacement time series as well as time series for new stations to be used in the DTRF2020 update to reduce non-linear station motions.

We extended the DTRF2020 by using the provided extension series and the NTL input data until 2023. We analyzed the extended station position, datum parameter (origin and scale) and Earth Orientation Parameter time series, introduced additional discontinuities and accounted for post-seismic deformation of stations affected by earthquakes.

We present the DTRF2020 update solution (i.e. DTRF2020-u2023) and discuss the consistency of the former and the extension series. In addition, we discuss the results of comparisons of the updates computed by the three ITRS Combination Centers, which reflect the internal accuracy achieved by today's ITRS realizations.

How to cite: Seitz, M., Bloßfeld, M., Rudenko, S., Zeitlhoefler, J., and Angermann, D.: DTRF2020_u2023: The Update of DTRF2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4041, https://doi.org/10.5194/egusphere-egu25-4041, 2025.

The International Laser Ranging Service (ILRS) regularly contributes to the maintenance of the reference frame by providing daily and weekly combined time series of station coordinates and Earth Rotation Parameters (ILRSA from the ILRS primary ASI Combination Center) derived from individual Analysis Centers (ACs) solutions, using LAGEOS-1/-2 and Etalon-1/-2 satellite data.

The inclusion of additional satellites in the ILRS official products has been under discussion since years within the ILRS Analysis Standing Committee and the launch of LARES-2 in July 2022 has been considered a real opportunity to improve the product quality. LARES-2 is a LAGEOS-type satellite specifically designed for high-accuracy satellite laser ranging.

The inclusion of LARES-2 as the fifth satellites of the constellation contributing to the routine products foresees a preliminary analysis to model stations' long-term systematic errors related to LARES-2.

The approach to manage the systematic errors is the same used for the ITRF2020 contributions: ACs simultaneously estimate station coordinates and range biases to determine a combined ILRSA set of long-term mean range biases for LARES-2, to be applied in the data analysis.

The identified systematic errors are reported in the ILRS Data Handling File (DHF), which is closely linked to the target signature model.

Preliminary time series of products including LAGEOS/ETALON/LARES-2 are available and an enhanced quality in the estimated station coordinates is evident, particularly in the UP component.

This presentation will address the status of the LARES-2 inclusion to the ILRS official products, emphasizing the quality of estimated parameters.

How to cite: Sarrocco, D., Luceri, V., Basoni, A., Vespe, F., and Blossfeld, M.: LARES-2 in the ILRS official products: analysis and current status, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4085, https://doi.org/10.5194/egusphere-egu25-4085, 2025.

The global geodetic parameters are essential for the realization of an International Terrestrial Reference Frame (ITRF), which has broad geophysical and geodetic applications. With well-distributed global tracking stations and continuous observations, GNSS is suited to providing high quality geodetic parameters, including geocenter coordinates (GCCs) and Earth rotation parameters (ERPs). However, the spurious draconitic signals have been observed in GNSS-based geodetic products. Fortunately, the fast development of multi-GNSS and LEO satellite techniques in recent years provides new opportunity to improve the determination of geodetic parameters by combining observations from constellations with different orbital characteristics. In this study, we perform the integrated precise orbit determination (IPOD) under the ITRF2020 with dual-system GPS/Galileo observations from the Sentinel-6A satellite and 61 ground stations for geodetic parameter estimation. The effects of the LEO solar radiation pressure (SRP) model are analyzed and the contribution of the multi-GNSS combination and the LEO is investigated.

Three Sentinel-6A macro models, from the manufacturer, the German Aerospace Center (DLR) and the University of Colorado and Jet Propulsion Laboratory (UoC/JPL), are used to perform GPS-based IPOD solutions to investigate the impact of LEO SRP model on geodetic parameter estimation. The relationship between the estimated constant SRP scale and sun elevation is first analyzed. The estimated SRP scale based on the UoC/JPL macro model is found to have a weaker correlation with sun elevation compared the other two macro models. By comparing the geodetic parameters obtained using different macro models, we find that the GCC-Z estimates are more sensitive to the LEO priori SRP model than the GCC-X/Y and ERPs, and the best solution with the smallest amplitude in 3 cpy frequency is achieved by UoC/JPL macro model.

Based on the UoC/JPL macro model, we further investigate the performance of the geodetic parameter estimation in IPOD with dual-system GPS and Galileo observations. The introduction of the LEO improves the ERPs estimates, with a reduction in the length of day (LoD) formal error of about 60%, and a reduction in the drift rate of the GNSS-derived dUT1 away from the IERS 20 C04 reference value of over 30%. The introduction of the LEO also improves the GCC estimates with a reduction in GCC-Z formal error and STD value by about 20% and 10% respectively. Compared to single system solution, the combination of GPS, Galileo and the LEO obtains the most stable GCC estimates with the smallest STD values, except for the GCC-Z for the period above 30 days, mainly due to the failure to eliminate the Galileo-induced 3 cpy spurious signal. However, the introduction of Sentinel-6A also induces the spurious annual signal due to its SRP model deficiency. Though this deficiency can be partly compensated by changing the parameterization of SRP scale factor from constant to piece-wise constant, the influence of residual errors of LEO SRP modelling is still visible in the Z component of GCC. These results indicate that refining the a priori macro model of LEO satellite is necessary to obtain accurate geodetic parameters in IPOD with multi-GNSS.

How to cite: Zhao, Y., Zhang, K., Li, X., Fu, Y., and Yuan, Y.: Global geodetic parameter estimation using the combination of GPS, Galileo and LEO satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4664, https://doi.org/10.5194/egusphere-egu25-4664, 2025.

A high-precision Terrestrial Reference Frame (TRF) is essential for accurately monitoring geophysical activities. Currently, India lacks its own Regional Reference Frame (RRF) and relies on the global frame for local applications. With the recent installation of more than 1000 GNSS stations forming the so called CORS (Continuously Operating Reference Stations) network by the Survey of India (SoI), the need for a precise RRF for India has become evident.

The RRF can be realized using either a conventional secular Multi-Year Reference Frame (MRF) or a (geocentric) Epoch-based Reference Frame (ERF). An MRF is realized by aligning the regional network to a global frame such as the ITRF or IGS TRF. However, the accuracy of MRFs diminishes over time as coordinates are extrapolated beyond the observation period using linear velocities. Additionally, MRFs provide limited geophysical information and can’t be utilized with desired accuracy for quasi-instantaneous applications or after large earthquakes.

To address these limitations, this study aims to develop an ERF for the Indian CORS sub-network by adopting the methodology introduced by Kehm (2022) for creating a geocentric ERF in Latin America. The proposed ERF ensures that the frame's origin aligns with the Earth's instantaneous center of mass across all time scales within the observation period.

In this presentation, we will outline the approach to develop the Indian ERF, which involves combining weekly normal equations from global GNSS, SLR, and VLBI networks. Specifically, SLR determines the origin, SLR and VLBI jointly determine the scale, and a homogeneously distributed global GNSS network is used to realise the orientation of the frame. The results will be compared to those obtained using the conventional MRF realization approach. Furthermore, an independent validation strategy will be implemented to evaluate the accuracy of the developed ERF.

How to cite: Kushwaha, R., Bloßfeld, M., Kehm, A., Balasubramanian, N., and Dikshit, O.: Initial Findings on Epoch-Wise Realization of a Regional Reference Frame Using Indian CORS Sub-Network Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5046, https://doi.org/10.5194/egusphere-egu25-5046, 2025.

Earth Rotation Parameters (ERPs), including polar motion (PM) and length of day, are crucial for describing the motion of the Earth's axis of rotation and linking the terrestrial and celestial reference system. ERPs can be categorized into long-term components and sub-daily components with periods shorter than two days. For the sub-daily ones, they reveal the impact of ocean tides, atmospheric tides, and other factors on Earth's rotation over short timescales, providing valuable insights into the dynamic process of Earth's motion. Compared to other techniques such as Satellite Laser Ranging, Very Long Baseline Interferometry, and Doppler Orbitography and Radiopositioning Integrated by Satellite, Global Navigation Satellite System (GNSS) technique offers advantages such as a densely distributed global station network, low equipment costs, continuous data tracking and high data sampling rate, making it particularly suitable for studying sub-daily PMs.

Since 2020, the Beidou Satellite Navigation System (BDS) has been officially completed and put into operation. Comparing with GPS, GLONASS, and Galileo, BDS has hybrid constellations with MEO and IGSO satellites which could bring new features into the derived sub-daily PMs. Therefore, this study first focuses on the precision of sub-daily PMs derived from BDS only. All the sub-daily PMs is based on 3-arc-length solutions with a 1-h temporal resolution. The results show that, compared to MEO-only, the addition of IGSO can reduce PMX from 183 to 161μas. For PMY, the addition of IGSO shows a similar improvement, reducing it by approximately 10%. Secondly, we transforme the time series of sub-daily PMs from different systems into the frequency domain by Fast Fourier transform (FFT) to identify and analyze those tidal and non-tidal signals. The results of spectral analysis indicate that the more diverse constellation configuration can effectively reduce the impact of spurious signals especially nearby 28-h term. In addition, more detailed comparisons and analyses with respect to the PMs derived from GPS, GLONASS, and Galileo are also presented. Furthermore, we also analyze the impact of weighting scheme in multi-GNSS combined solutions. Properly adjusting the weights of BDS can effectively improve the accuracy of sub-daily PMs. Finally, we assessed the GNSS-based empirical models with three priori empirical models, IERS2010 model, Gipson model and Desai-Sibois model. Multi-GNSS model with different constellation configurations shows the best consistency with the priori model.

How to cite: Yao, X., Li, X., Yuan, Y., and Zheng, H.: Analysis and Comparison of Sub-daily Polar Motion Derived from BDS, GPS, GLONASS and Galileo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5417, https://doi.org/10.5194/egusphere-egu25-5417, 2025.

The accuracy of the Terrestrial Reference Frame (TRF) realization is currently constrained by systematic errors among the four main space-geodetic techniques: GNSS, VLBI, SLR, and DORIS. Terrestrial local ties connect physical survey points from local surveys, which will introduce errors in the TRF and transform uncertainties across all geodetic observations. To achieve the GGOS goals of 1 mm accuracy and 0.1 mm/yr stability for TRF realization, space missions equipped with multiple space-geodetic techniques are proposed, such as GRASP (Geodetic Reference Antenna in Space), E-GRASP, and GENESIS. Space co-location will complement ground-based co-location and enhance the TRF.

We are currently developing the simulated space-geodetic observations of various missions and assessing their potential impact on the TRF including station coordinates, Earth Orientation Parameters, and geocenter. The simulations will take into account VLBI tracking GNSS satellites and geodetic satellites, considering three major error sources: measurement noise, clock error, and zenith wet delay. Through these thorough analyses, we will explore the requirements of this new type of observable. The novel measurement concept has the potential for not only solving the inconsistencies and biases between the different geodetic techniques, but also establishing frame ties between the kinematic and dynamic reference frames.

How to cite: Liu, H., Zou, X., Liu, B., Zhao, M., and Pan, J.: Simulation studies on VLBI tracking satellites and the potential to enhance TRF, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5546, https://doi.org/10.5194/egusphere-egu25-5546, 2025.

We report on JTRF2020-u2022, the first update of JTRF2020, the most recent terrestrial reference frame (TRF) solution computed at Jet Propulsion Laboratory (JPL). Determined with SREF -a square-root information filter and Dyer-McReynolds smoother algorithm, JPL frame products lend themselves to being easily updated as long as frame inputs from the four space-geodetic technique consistent with the frame-defining data set are available. 

Adopting the conceptual framework of Bayesian update inherent to any Kalman filter formulation, SREF uploads the latest estimate of JTRF2020 state and its covariance and updates it by assimilating at daily intervals the extended frame inputs made available by IGS (IGSR3-igr3.atx), IVS (ivs2023b), ILRS (ilrsav86), and IDS (idswd23) from 2021 through the end of 2022 (DOY 330, GPS Week 2237). Afterwards, with SREF running in forecast mode, station position predictions are generated through the end of 2027 (DOY 365, GPS Week 2503).    

Discussions will focus on the peculiarities of the extended frame inputs used to compute JTRF2020-u2022 in relation to those adopted to generate JTRF2020, on the data pre-processing itself, and on the way in which the updated frame is constructed . We outline properties of  the updated TRF in terms of its frame-defining transformation parameters and present a quality assessment of  JTRF2020-u2022.

How to cite: Abbondanza, C., Chin, T. M., Gross, R. S., and Heflin, M. B.: JTRF2020-u2022: The First Update of JTRF2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6631, https://doi.org/10.5194/egusphere-egu25-6631, 2025.

Global Navigation Satellite Systems (GNSS) rely on one-way signal travel time measurements from satellites to receivers. To ensure accurate ranging, GNSS must estimate and compensate for clock offsets on at least one end of the transmitter-receiver system. Consequently, clock offsets are highly correlated with GNSS-derived parameters such as station coordinates, tropospheric delay estimates, satellite radial orbit parameters, and apparent geocenter coordinates. Improper handling of clock offsets can lead to their absorption into these parameters, degrading geodetic product accuracy. Traditionally, clocks have been handled within individual techniques without being specially addressed. However, some research efforts and experimental trials have explored using VLBI to synchronize clocks for GNSS and refining clock models to reduce correlations with other estimated parameters in GNSS, thereby improving overall precision.

With recent advancements, high-precision optical clocks and fiber-optic time transfer technologies provide new possibilities for enhancing clock synchronization in GNSS. Optical fiber offers a stable, interference-free medium for time and frequency transfer, eliminating atmospheric effects such as ionospheric and tropospheric delays that impact GNSS-based synchronization. Moreover, fiber-optic time transfer is inherently two-way, removing the need for external clock offset estimation. Thus, fiber-optic clock synchronization represents the most precise timing technique currently available. Establishing a common clock by connecting multiple GNSS receivers via optical fiber could significantly reduce the number of estimated clock parameters in GNSS solutions, leading to improved geodetic measurement precision and a more accurate geodetic reference frame.

Despite its potential, the approach of implementing a common clock with optical fiber for GNSS receivers remains largely untested. Although optical fiber links have been successfully used in clock synchronization, their integration into GNSS receiver clocking is still in an experimental stage. Notable existing efforts include: (1) the Geodetic Observatory Wettzell, where multiple receivers are connected to a single clock via optical fiber, representing a local baseline setup, and (2) the GFZ experiment, where a receiver is linked to the ultra-stable clock of PTB, representing a regional baseline approach.

This study characterizes existing fiber-optic connections among GNSS receivers to identify practical challenges and evaluate their impact on GNSS parameter estimation. We process data from receivers sharing a common clock using Bernese GNSS Software. Initially, PPP will be performed to compare GNSS-derived clock parameters across receivers sharing a common clock, verifying the effectiveness of fiber-optic clock synchronization. Following this validation, we will leverage GNSS-derived clock parameters to evaluate inter-receiver clock differences measured via optical fiber. Subsequently, we will implement a strategy in which only one receiver’s clock parameters are estimated, using fiber-measured clock differences as a priori constraints for other receivers in the PPP solution. This approach reduces the number of estimated clock parameters and serves as a preliminary test of the feasibility of a GNSS common clock framework.

Future developments will focus on refining our analysis framework to enable simultaneous estimation of GNSS receivers operating under a common clock. This research contributes to the broader goal of integrating ultra-stable clocks into global GNSS networks, ultimately enhancing the stability of geodetic reference frames and improving GNSS-derived geodetic products.

How to cite: Wang, Z., Hugentobler, U., Männel, B., and Rodríguez-Villamizar, J.: Common Clock for GNSS Receivers: Characterization of Parameters Estimated with GNSS Receivers Connected to the Same External High-Precision Clock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7197, https://doi.org/10.5194/egusphere-egu25-7197, 2025.

The global high-precision Terrestrial Reference Frame (TRF) is determined through the combination of the four space geodetic techniques: VLBI, SLR, GNSS, and DORIS. The multi-technique combination heavily relies on the common objects or parameters, i.e., the ties, which link the different techniques. Current realizations of the International Terrestrial Reference Frame (ITRF) employ local ties and Earth Orientation Parameter (EOP). Additional ties such as tropospheric ties and satellite orbit ties are being explored. Another promising approach is using clock ties, where co-located instruments connected to a common clock enable intra- and inter-technique clock tie modeling.

Clock ties between GNSS and VLBI are of particular interest as (1) GNSS provides dense observations at every epoch, allowing the epoch-wise estimation of clock parameters, and (2) VLBI typically relies on clock modeling due to the insufficient number of observations per epoch. Using the GNSS and VLBI co-location stations during VLBI CONT campaigns, we demonstrate inter-technique clock agreements within 0.1 and 0.2 ns for short (24-hour) and long (15-day) periods, respectively. We further explore the application of clock ties in the GNSS and VLBI integrated solution, focusing on the impact on station coordinates and tropospheric delays. We also address the challenges of modeling deterministic and stochastic components of the clock ties, highlighting their potential to improve the precision of TRF realizations.

How to cite: Wang, J., Balidakis, K., Heinkelmann, R., Ge, M., and Schuh, H.: Applying Clock Ties in GNSS and VLBI Integrated Solution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7460, https://doi.org/10.5194/egusphere-egu25-7460, 2025.

A Global Geodetic Reference Frame (GGRF) is a fundamental requirement to relate measurements taken from anywhere on the Earth. It provides the basis on which a broad spectrum of scientific and industrial applications rely, and is crucial in any field where precise location information is necessary, including monitoring climate change, agriculture, and changes in groundwater.
The working group Satellite Geodesy at the Institute of Geodesy (IFG), Graz University of Technology (TUG) provide a wide range of of products which are processed and published to the international community such as gravity field ans mass transport solutions, Precise Orbit Data (POD) of Low Earth Orbit (LEO) satellites and Global Navigation Satellite Systems (GNSS) station networks and much more. The products are utilized by various organizations, such as the International Combination Service for Time-variable Gravity Fields (COST-G) of the International Association of Geodesy (IAG), the International GNSS Service (IGS) or the European Copernicus POD Service Quality Working Group (CPOD). A consistent and accurate GGRF is the foundation of all our products and, as such, is essential to ensure the quality of our in-house computed products.
A GGRF is established and maintained by an international community, culminating in the International Terrestrial Reference Frames (ITRF). The latest version, ITRF2020, is based on four space geodetic techniques: GNSS, VLBI, SLR, and DORIS. In ITRF2020, GNSS was ignored in the calculation of the geocenter motion and the estimation of the reference system scale because it was considered too inaccurate. 
In this work we present our approach to estimate the geocenter motion and to improve the scale estimation using only GNSS. 
We discuss the problems of combined estimation of geocenter motion, reference system scale and satellite antenna center offsets and variations in GNSS only reference frame estimation. We analyze the results and implications for GNSS products and station position time series.

How to cite: Dumitraschkewitz, P., Mayer-Gürr, T., and Süsser-Rechberger, B.: Scale and Geocenter determination by GNSS only, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8525, https://doi.org/10.5194/egusphere-egu25-8525, 2025.

GNSS station operators and network analysers face the challenge of achieving consistent phase center corrections (PCCs), particularly since multi-GNSS calibrations are not available for all antennas. To address this issue, a global initiative involving nine calibration organizations has launched a comprehensive ring calibration campaign. This collaboration aims to enhance the consistency of calibration methods and establish a robust quality assessment framework by sharing six structurally diverse antenna samples for calibration. The recommended methods by the International GNSS Service (IGS), including anechoic chamber and field robot calibration methods, are participating with the aim of defining a global benchmark for the accuracy and reliability of receiver antenna PCCs.

Over the past year, the campaign has made significant progress. Measures and methods to easily compare the PCC patterns and define a benchmark value for consistent PCCs have been established. In this contribution, we present the latest results of this campaign. We demonstrate in the pattern domain that the consistency among the system/frequencies per receiver antenna design varies around an uncertainty level of ±1 mm, with an elevation-dependent effect also needing consideration. In the position domain, we present system-specific PPP results per antenna and facility. For example, the variation among different antennas and facilities for classical GPS ionosphere free linear combination is generally below 2-3 mm for the horizontal component and below 5 mm for the vertical component when comparing calibration sets among the various facilities. We also present comprehensive and effective comparison methods for the pattern domain and evaluation tools for the position domain that are essential for establishing a globally fair and transparent benchmark for receiver antenna PCC calibration and verification processes.

How to cite: Kersten, T., Billich, A., Sutyagin, I., Kröger, J., and Schön, S.: Progress Update on a Global Collaboration for GNSS Receiver Antenna Calibration: Results from the IGS Ring Calibration Campaign (IGS ringCalVal), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9053, https://doi.org/10.5194/egusphere-egu25-9053, 2025.

High precision satellite laser ranging observations to the geodetic spherical satellites are now available for almost five decades, and their analyses are critical to the ongoing realisation of an accurate terrestrial reference frame. Inevitably and importantly the ground-station technologies have improved considerably over time, such that systematic range-measurement errors are now for the major stations at the few mm level. Such hardware improvements, as well as improved analyses procedures instigated by the ILRS, have prompted a review of the measurements made mostly by a number of European network stations in the early 2000s that used time-of-flight equipment known to have systematic, range-dependent errors of up to 10mm. These timers were investigated at the UK Space Geodesy Facility, Herstmonceux in the early 2000s and the range dependencies measured against a highly accurate event timer; however, some of the implications of those results have not yet fully been utilised in data processing for ITRF realisations.

In this poster we review this work and report on our new data analyses that include the range-dependent corrections, commenting on the impact on the quality of the stations’ height time series.

How to cite: Appleby, G. and Susnik, A.: Further progress to improve the accuracy of satellite laser ranging data: impact on geodetic height time series of removal of range-dependent systematic errors at some European stations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10241, https://doi.org/10.5194/egusphere-egu25-10241, 2025.

JPL has developed a terrestrial reference frame (TRF) based on combining space geodetic techniques at the observation level. The current version includes observations from the Global Positioning System (GPS), Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI); and it has been shown to be competitive with the international standard (ITRF2020) in terms of fundamental frame parameters (origin and scale) and their temporal evolution, both linear and seasonal. In this work, we build on the current processing infrastructure and add Doppler Orbitography by Radiopositioning Integrated on Satellite (DORIS) observations to the combination. The four-technique solution strategy uses space ties in low-Earth orbit to connect SLR, GPS and DORIS and ground ties to connect VLBI to GPS. This solution can be viewed as a pathfinder for the upcoming GENESIS mission which will provide a space tie for all 4 techniques. Additionally, we revise parametrization of the SLR range biases to improve retrieval of the scale. Finally, we discuss future enhancements to the TRF realization process. These enhancements include recovering the time-variable gravity field by jointly using observations from the frame realization and GRACE / GRACE-Follow On missions.

How to cite: Peidou, A., Haines, B., Bertiger, W., Conrad, A., Desai, S., Murphy, D., Naudet, C., and Ries, P.: Geodetic Technique Combinations at the Observation Level: Advancements in Terrestrial Reference Frame Recovery, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11071, https://doi.org/10.5194/egusphere-egu25-11071, 2025.

The DORIS Ultra-Stable Oscillators (USO) onboard Sentinel satellites are sensitive to the South Atlantic Anomaly (SAA) effect. While this sensitivity is not particularly significant for the precise orbit determination (POD) of the Sentinel-3A, Sentinel-3B, and Sentinel-6A satellites, it becomes crucial when estimating station positions. Previous studies have shown notable degradation in station position accuracy for stations located within the SAA region when using single-satellite solutions.
This study aims to evaluate the impact of using GPS clock as the modelled DORIS USO, provided by the CNES POD team, on station position estimation derived from single-satellite solutions of Sentinel-3A and Sentinel-6A. Single-satellite solutions were computed both with and without GPS clock corrections and were compared to the SARAL single-satellite solution, which serves as a reference due to its USO being minimally or not at all affected by the SAA. Our analysis investigates whether incorporating GPS clock corrections as a modeled DORIS USO can effectively mitigate the impact of the SAA on station position estimations in the affected regions. 

How to cite: Capdeville, H., Mezerette, A., Gravalon, T., Lemoine, J.-M., Moyard, J., Mercier, F., and Couhert, A.: Analyzing the Impact of GPS Clock as the modelled DORIS USO on Station Position Estimation for Sentinel Satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11124, https://doi.org/10.5194/egusphere-egu25-11124, 2025.

Global Terrestrial Reference Frames (TRFs) are regularly provided by three International Terrestrial Reference System (ITRS) combination centres (CCs) of the International Earth Rotation and Reference Systems Service (IERS), located at the Institut national de l’information géographique et forestière (IGN), at the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration (NASA), and at the Deutsches Geodätisches Forschungsinstitut (DGFI) of the Technical University of Munich (TUM). All three CCs use different methodologies and assumptions to compute a global TRF.

In the framework of the IAG-IERS Joint Working Group 1.2.4 for the evaluation of the terrestrial reference frames, we analyze the impact of three different 2020 TRF realizations (provided by the CCs) on Satellite Laser Ranging (SLR) data processing using a development version of the Bernese GNSS Software (BSW).

First, to obtain the total effect of the TRF realization on the SLR satellite orbits and the post-fit observation residuals, the station coordinates are fixed to the a priori values. Afterwards, the set of excepted core stations used for a proper datum definition is compared for the different TRFs. Finally, a state-of-the-art SLR data processing is performed, where orbit parameters and range biases along with global geodetic parameters, e.g., Earth rotation parameters and station coordinates, are co-estimated.

How to cite: Geisser, L., Susnik, A., Arnold, D., Dach, R., and Jäggi, A.: Impact of Different TRF Realizations on SLR Data Processing in the Benese GNSS Software, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11575, https://doi.org/10.5194/egusphere-egu25-11575, 2025.

New realizations of the International Terrestrial Reference System (ITRS) were recently released by the three ITRS combination centers: ITRF2020 by IGN (France), DTRF2020 by DGFI-TUM (Germany) and JTRF2020 by JPL (USA). The three solutions are based on the same reprocessed data from the four space geodetic techniques (DORIS, GNSS, SLR, VLBI). However, the strategies used by the three ITRS centers to combine these input data into their respective solutions differ in several key aspects, such as the modeling of time-varying station trajectories, the connection of the station networks of the four techniques into a unique common frame, and the choices made to define the origin and scale of that frame.

This presentation compares the ITRF2020, DTRF2020 and JTRF2020 solutions and discusses how different aspects of the combination strategies employed by the three ITRS centers affect their solutions in terms of origin, scale and geometry. This comparison and discussion covers two main aspects: (1) individual station trajectories in the three solutions, and their ability to accurately describe the Earth’s time-varying shape, and (2) origins, scales (and orientations) of the station coordinates of each technique in the three solutions.

How to cite: Barnéoud, J., Rebischung, P., Gobron, K., de la Serve, M., Collilieux, X., and Altamimi, Z.: A comparison of ITRF2020, DTRF2020 and JTRF2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11660, https://doi.org/10.5194/egusphere-egu25-11660, 2025.

Earth deformation monitoring is an important aspect in the realization and investigation of reference frame. Global Navigation Satellite Systems (GNSS) is well-established technique to estimate the Earth surface velocity field and the deformation rates at the location of permanent stations. We make use of GNSS coordinate time-series to estimate horizontal and vertical velocity fields. However, one of the challenges is the superposition of a variety of signals and the contribution of noise and random processes in the GNSS time-series that adds to the complexities in extraction of the signal of interest in a straightforward manner. Therefore, we need to employ signal processing methods in the analysis of GNSS time-series signal separation or mode decomposition. In addition, the geometry of GNSS positioning and some other effects, e.g., solar radiation pressure-induced draconitic year etc. cannot be neglected. On the other hand, because of unpredictable mechanisms, e.g., earthquakes, coordinate time-series may experience discontinuities. For this reason, we employ mathematical tests to detect, estimate and remove these mechanisms to conclude the velocity field. In addition to signal separation and estimation of a realistic velocity field, the uncertainty estimation is also important for geoscientific applications. For this purpose, we take advantage of the variance and covariance component estimation methods to estimate not only a realistic velocity field, but also for realistic estimation of uncertainties. Studying of uncertainties is of importance and applicable in the sensitivity analysis. In some cases, we would like to know the sensitivity of the GNSS time-series to specific signals, e.g., solid Earth and mantle signals etc. In this study, we will present our work-in-progress approach for GNSS time-series analysis by combining data-driven and analytical approaches to have a better understanding of GNSS time-series with focus on the velocity field of our study area in central Europe.

How to cite: Karimi, H., Hugentobler, U., Abolghasem, A. M., Heydari, M., and Friedrich, A. M.: A new approach for GNSS time-series analysis with focus on uncertainty and sensitivity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11796, https://doi.org/10.5194/egusphere-egu25-11796, 2025.

To ensure inter-operability and consistency of various geodetic products for Solid Earth science and operational geodesy applications, a long-term global terrestrial reference frame is required, i.e., the International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF). As one of the key parameters in the determination of the ITRF, geocenter motion must be precisely estimated. Space geodetic techniques such as Satellite Laser Ranging (SLR), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Global Navigation Satellite Systems (GNSS), which connect satellites and ground stations, are capable of determining geocenter motion. However, only the SLR technique is currently included in the realization of the ITRF, despite GNSS being widely regarded as a promising technology. Compared to SLR-based solutions, GNSS exhibits lower accuracy due to various modeling issues, including deficiencies in non-gravitational force models. In recent years, numerous studies have demonstrated the significant potential for improving geocenter coordinate estimation through the integration of ground-based observations and space-based observations from low Earth orbiters (LEOs). Nevertheless, the full contribution of LEOs to geocenter motion estimation remains underexplored, largely due to the limited temporal coverage and the small number of LEOs available..

To evaluate the extent of associated improvements, a network of 150 ground tracking stations and up to 13 LEOs (GRACE-A/B/C/D, SWARM-A/B/C, JASON-1/2/3, SENTINEL-3A/3B, and SENTINEL-6A) was processed over a 20-year period (2004–2024). Three solutions were investigated: (1) a reference solution utilizing only ground-based GNSS observations; (2) a combined ground- and space-based solution employing a reduced-dynamic (DYN) strategy for LEO orbit determination; and (3) a combined ground- and space-based solution employing a kinematic (KIN) strategy for LEO orbit determination. All solutions were implemented in accordance with the processing strategy of the IGS's 3rd reprocessing campaign.

In this contribution, we evaluate contribution of space-based observations to geocenter motion estimation through spectral analysis and external comparisons. Significant improvements are observed in the combined ground- and space-based solutions, particularly in enhancing geocenter motion stability and mitigating certain artificial signals. Among the three solutions, the GNSS/LEO integrated solution employing the KIN strategy for LEOs demonstrates a substantial reduction in draconitic errors compared to the others.

How to cite: Tang, L., Männel, B., Wang, J., Nie, L., and Wickert, J.: The contribution of multi-LEOs to geocenter motion estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12120, https://doi.org/10.5194/egusphere-egu25-12120, 2025.

The classical VLBI delay model is built on the assumption that incoming radiowaves are planar, which holds true for observations of distant celestial radio sources due to their immense distances. However, when applied to VLBI observations of satellites in near-Earth orbit, this assumption becomes inadequate, as the curvature of the wavefronts cannot be neglected. Accurately modeling of these delays is crucial for achieving the precision required in satellite-based VLBI studies. To address this challenge, several near-field delay models have been proposed in the literature. In this study, we focus on four near-field VLBI delay models, comparing their methodologies, and resulting accuracy across a range of orbital configurations. By systematically evaluating these models under varying geometric and dynamic conditions, we aim to identify their strengths, limitations, and potential discrepancies.

How to cite: Sert, H., Karatekin, O., and Dehant, V.: Comparison of near-field delay models for Earth-orbiting satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12493, https://doi.org/10.5194/egusphere-egu25-12493, 2025.

Information about satellite antenna phase center offsets (PCOs) is crucial for high-precision applications of global navigation satellite systems. Pre-launch manufacturer calibrations of the PCOs are available for all individual BDS satellites and three frequencies: B1, B2, and B3. With the imminent retirement of BDS-2 and the superior quality of B1C/B2a signals, the International GNSS Service (IGS) has launched a campaign for BDS-3 and QZSS phase center correction (PCC) calibration. However, only the IF combination of B1C/B2a is required. Considering the upcoming multi-GNSS and multi-frequency applications, the consistency of PCO values across different frequencies and GNSS is important.

We present the estimation of BDS-3 satellite antenna PCCs consistent with the International Terrestrial Reference Frame (ITRF2020) from the ionosphere-free linear combinations of B1I/B3I and B1C/B2a. The results demonstrate that the nadir-angle-dependent phase center variations (PCVs) of the same satellite block type have fairly good consistency. The mean horizontal PCOs of the different frequencies agree at the millimeter level. The X-PCOs show a bias of about 1 cm compared to the manufacturer calibrations, whereas the Y-PCOs are free of such bias. For Z-PCOs, some SECM satellites exhibit unexpected long-term variations and/or abrupt jumps, while all CAST satellites remain stable. The mean estimated values of B1C/B2a and B1I/B3I for BDS-3M-CAST, BDS-3M-SECM, and BDS-3I-CAST are (-15.9, -13.5), (-17.8, -3.0), and (+26.9, +24.0) cm larger than the CSNO values, respectively.

By applying the estimated PCCs instead of the CSNO values, the precise orbit precision can be improved by 3.6-12.2%, and the scale factors determined by BDS solutions exhibit good consistency with the IGS20 frame, with mean scale differences below 0.10 ppb for both frequency combinations.

Furthermore, CSNO values for SECM satellites are excluded from delivering the TRF scale by BDS-3 as they still remain questionable. Although the scale delivered by GPS and Galileo shows good consistency, with +0.84 and +0.73 ppb compared to ITRF2020, the scale difference of BDS-3 with respect to ITRF2020 is -0.84 and -0.92 for B1C/B2a and B1I/B3I. These results demonstrate the consistency of different frequencies for BDS-3 but also highlight the discrepancy within GNSS, specifically between BDS-3 and GPS/Galileo.

How to cite: Li, J. and Guo, J.: Consistency of BDS-3 transmit antenna phase center offsets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12548, https://doi.org/10.5194/egusphere-egu25-12548, 2025.

In the context of its contribution to the second yearly update of the 2020 realization of the International Terrestrial Reference Frame (ITRF2020), the International DORIS Service (IDS) has undertaken the estimation of DORIS station positions and velocities, as well as Earth Rotation Parameters (ERPs), derived from DORIS data. These computations are based on the latest weekly multi-satellite series from the five IDS Analysis Centers and the IDS Associated Analysis Center, covering data from 2024 and 2021 backward.

The primary objectives of this study are to evaluate the DORIS contribution to this update of the ITRF2020 in terms of: (1) geocenter motion and scale, (2) station positions and week-to-week position repeatability, (3) EOPs, and (4) a cumulative position and velocity solution. Additionally, this study examines the benefits of new models as well as the implementation of South Atlantic Anomaly (SAA) mitigation strategies on specific DORIS missions. Particular focus is placed on the enhanced stability of the IDS-derived scale since late 2012.

How to cite: Moreaux, G., Lemoine, F., Capdeville, H., Štěpánek, P., Otten, M., Nahmani, S., Pollet, A., and Schreiner, P.: IDS contribution to the second update of the ITRF2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12833, https://doi.org/10.5194/egusphere-egu25-12833, 2025.

This study investigates the estimation of the Length of Day (LOD) using DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) RINEX data from 2015 to 2023, comparing results with  the IERS 20 C04 model. Observations from 10 satellites were analyzed using DORIS-specific modification of the Bernese GNSS software, with varying durations of data availability across the nine years. The analysis explores the variability in Earth's rotation, attributing changes to dynamic factors influencing angular momentum. Various solution versions  with different parameter constraints were evaluated. Statistical analysis reveals that the low constrained cross track once per revolution parameters provided less  reliable results.

Key findings reveal a close alignment between DORIS-derived LOD values and the IERS 20 C04 model, for satellite combinations, with a weighted mean of 7 µs and a weighted standard deviation of 87 µs . Single-satellite analyses highlight the contributions of specific satellites, such as Cryosat, Saral, and Sentinel-6, in capturing unique geophysical processes. Improved data precision and modeling were observed over the years, reflecting advancements in satellite instrumentation and operational protocols. Statistical analysis emphasizes combining multiple satellite datasets for more reliable LOD estimates, as single-satellite solutions showed higher variability and biases.

Spectral analysis identifies dominant periodic signals, such as annual and semi-annual cycles, and variations induced by tidal and orbital mismodeling. The impact of relativistic effects was evaluated, demonstrating the significant role of Lense-Thirring corrections in precise LOD modeling. A comparison of different subdaily  motion models revealed subtle differences in periodic signal amplitudes. This work underscores the possibility of precise LOD estimation from DORIS data, on condition of high-quality satellite data and refined modeling techniques for accurate Earth rotation studies, providing insights into temporal variability in LOD and contributing to geodetic and geophysical research.

How to cite: Stepanek, P., Kumar, V., and Filler, V.: Estimation of the Length of Day (LOD) from recent DORIS Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13470, https://doi.org/10.5194/egusphere-egu25-13470, 2025.

The NASA GSFC/UMBC JCET ILRS Analysis Center supports the International Laser Ranging Service (ILRS) by operating as an Analysis Center (AC), submitting regular SINEX solutions on a daily and weekly basis, acting as the backup combination center (ILRSB), and conducting validation of ILRS tracking stations. These validations are essential for new stations or stations implementing significant changes. In support of the ILRS Analysis Standing Committee (ASC), the JCET AC processes data to the ILRS “ITRF” satellites (LAGEOS-1, LAGEOS-2, LARES, LARES-2, Etalon-1, and Etalon-2) and submits different SINEX solutions containing Earth orientation parameters and station coordinates daily and weekly. We provide an overview of these analysis activities and present the methods and results of our recent validation efforts, benchmarking the ILRSB results with the results obtained by ILRSA. We summarize the recent contributions of the Analysis Center, including the v85 (ITRF2020 & extension contributions), v80, v180 (LAGEOS1, LAGEOS2, Etalon1-2), as well as v90, v190 (including LARES-2). Additionally, we report on the validation activities that we perform for the ILRS Analysis Standing Committee, where the performance of new stations or stations undergoing system upgrades are evaluated with respect to the quality of their precision of their data and their bias stability. ILRS Stations that have undergone validation in the last six months include Matera (7941), and Yebes (7817). 

How to cite: Kuzmicz-Cieslak, M., Evans, K. D., Belli, A., and Lemoine, F. G.: Update on the activities of the NASA GSFC/JCET ILRS Analysis Center, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13490, https://doi.org/10.5194/egusphere-egu25-13490, 2025.

CODE (Center for Orbit Determination in Europe) acts as one of the analysis centers of the International GNSS Service (IGS). One of the most important products are the final series providing -- among others -- GNSS satellite orbits, satellite clock corrections and station coordinates. Currently it includes GPS, GLONASS, and Galileo satellites. The final solution series shall provide the user community a direct access to the IGS20 reference frame (the IGS-specific realization of the ITRF2020).

Regarding this purpose, the extension of the final products to other systems, in particular BDS and QZSS need a careful consideration not to degrade the access to the reference frame. We present a step-by-step inclusion of BDS (only satellites in MEO orbits) and all BDS satellites (apart from those ones in GEO orbits) using the new combined satellite antenna offsets recently computed by the IGS. Another investigation is related to the QZSS satellites where pre-launch satellite antenna calibrations are available.

As a result of the study, a potential extension of the CODE final solution series to a more complete multi-GNSS product is decided. 

How to cite: Dach, R., Brockmann, E., Arnold, D., Kalarus, M., Lasser, M., Schaer, S., Stebler, P., and Jäggi, A.: BDS and QZSS in CODE's final solution -- assessment of the impact , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14680, https://doi.org/10.5194/egusphere-egu25-14680, 2025.

Genesis is an upcoming satellite mission by the European Space Agency (ESA) that will integrate multiple space geodetic techniques on a single satellite at an altitude of 6000 km, including a dedicated Very Long Baseline Interferometry (VLBI) transmitter. This innovative, dynamic space geodetic observatory aims to establish highly accurate and continuous space ties, significantly enhancing the accuracy and stability of Terrestrial Reference Frames (TRFs). Including a VLBI transmitter will enable observations to Genesis using existing VGOS antennas and infrastructure, but several technical challenges must be addressed to ensure the success of VLBI observations.

A key open question is the choice of the satellite’s orbit, whether polar (97°) or inclined (60°). Additionally, the allocation of observation time between satellite and quasar observations must be carefully optimized. While sufficient VLBI observations of Genesis are needed to estimate accurate station positions, maintaining a good sky coverage of quasar observations is essential for precise tropospheric delay modeling, the major error source in VLBI measurements.

This simulation study addresses these points by evaluating various observation scenarios for two VGOS station networks, considering different orbital configurations and observation time distributions. Based on the determination of TRFs from weekly VLBI sessions over a two-year investigation period, we aim to identify the optimal setup for VLBI observations of Genesis.

How to cite: Kern, L., Wolf, H., Steinmetz, S., and Böhm, J.: Evaluating VLBI Scenarios for Genesis: Orbital and Observational Configurations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15312, https://doi.org/10.5194/egusphere-egu25-15312, 2025.

This study outlines the current status of DORIS data processing using the GipsyX software at the IGN-IPGP/JPL analysis center within the International DORIS Service (IDS). We detail the methodological evolution implemented since late 2023 for the ITRF2020-u2024, coinciding with the operational reactivation of the analysis center (AC).

Our analysis focuses on a comparative assessment of precise orbit determination (POD) results against SSALTO orbits, positioning estimates relative to the DPOD2020 reference frame, and Earth Orientation Parameters (EOPs) against the EOPC04 series. This enables a thorough evaluation of the consistency and accuracy of our products relative to established benchmarks.

In addition to describing these advancements, we highlight ongoing and planned developments aimed at enhancing processing capabilities. Among these, we present preliminary results from simultaneous multi-satellite data analysis, which incorporates separate modeling of ground and satellite clocks. These developments are expected to improve the temporal and spatial resolution of DORIS-derived geodetic products, ultimately contributing to the broader geophysical and climate-monitoring goals of the IDS.

How to cite: Pollet, A., Nahmani, S., and Bertiger, W.: DORIS IGN-IPGP/JPL Analysis Center: Current Status and Future Developments , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15635, https://doi.org/10.5194/egusphere-egu25-15635, 2025.

Genesis is an ESA mission dedicated to Global Navigation Satellite System (GNSS) Science, conducted by the ESA Navigation Directorate. Its primary objective is the contribution to the improvement of the International Terrestrial Reference Frame (ITRF) accuracy (1mm) and long-term stability (0.1mm/year). Secondary objectives include the contribution to a high number of other scientific disciplines (geodesy, geodynamics, earth rotation, geophysics, earth gravity field, atmosphere and ionosphere sciences, metrology, relativity…) [1].

On the industrial side, the company OHB Italia has been contracted by ESA as prime for the development, qualification, launch and 2 years operation of the mission, with a launch date in 2028 [2]. Antwerp Space (B), as the major sub-contractor of OHB-I, oversees the payload and geodetic instruments. Industrial activities were kicked-off in April 2024, the System Requirements Review was successfully closed-out in Q4 2024, and work is on-going towards a Preliminary Design Review in Q4 2025.

In parallel, on the scientific side, after a first successful Genesis Workshop held in February 2024 [3], a Genesis Science Exploitation Team was set-up and members appointed. The Genesis Science Exploitation Team are actively supporting the mission development (in particular consolidation of requirements) and will play a key role in its future exploitation.

The presentation will provide a high-level description of the mission, and provide the  programmatic status of Genesis.

[1]: Delva et al. Earth, Planets and Space 75, 5 (2023)

[2]: https://www.esa.int/Applications/Satellite_navigation/ESA_kicks_off_two_new_navigation_missions

[3]: https://www.esa.int/Applications/Satellite_navigation/The_geodetic_community_meets_Genesis

How to cite: Gidlund, S., Fusco, G., Waller, P., Morlet, C., Perez Lissi, F., Sakalauskaite, E., Enderle, W., Schoenemann, E., Berton, J.-C., Gini, F., and Navarro, V.: Overview of Genesis - an ESA mission at the Foundation of Navigation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15776, https://doi.org/10.5194/egusphere-egu25-15776, 2025.

In mid-2024, the IAG-IERS Joint Working Group 1.2.4 was established to complement the evaluation of the International Terrestrial Reference System (ITRS) realizations by the three ITRS combination centres (CC) of IERS with a special focus on the intercomparison of different global Terrestrial Reference Frame (TRF) solutions. The assessment aims at investigating conceptual differences of the three global ITRS realizations based on today’s user and application requirements. The main objectives of the JWG 1.2.4 include (i) the comparison of the combination strategies followed by the IERS ITRS CC; (ii) the assessment/quantification of station position time series differences between the ITRS realizations and w.r.t. geophysical models (e.g., loading displacements): (iii) the development and promotion of alternative rigorous (and independent) methods for the intercomparison of global TRF solutions (e.g., POD of low-, medium- and high-Earth-orbiting satellites); (iv) the development of methods and procedures for the quality control of TRF solutions.

Following a brief presentation of the structure of the JWG, we will give a status of its current activities. Then, we will introduce some of the benchmarks the JWG has identified to assess the quality of both global and regional TRF solutions. Finally, these benchmarks will be illustrated by their use on the latest ITRS 2020 realizations.

How to cite: Susnik, A., Moreaux, G., Ampatzidis, D., Krasna, H., Geisser, L., and Seitz, M.: IAG-IERS Joint Working Group 1.2.4 on the evaluation of the Terrestrial Reference Frames, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16930, https://doi.org/10.5194/egusphere-egu25-16930, 2025.

Set for launch in 2028, geodesy’s flagship mission GENESIS is equipped with the instruments of the four space geodetic techniques. The co-location satellite aims to improve the accuracy and stability of future realizations of the ITRF. However, VLBI observations to satellites are not standard and are not performed routinely yet. In the past, observations were limited to specific telescopes and setups. At the moment, most VLBI antennas are not capable of observing currently available satellite signals. This makes testing difficult, although further research on the VLBI component of GENESIS is urgently needed to achieve the accuracy for the mission goals. We present the newly accessible capability of the Australian VGOS telescopes to observe GNSS satellites in L-band.  With this new discovery, we are able to generate geodetic delay observables with a full continental-wide telescope array on a routine basis in the style of IVS observations. In particular, we report on a series of successful observations to satellites of the GPS, Galileo and BeiDou constellations with the AuScope 12-m antennas in Hobart, Katherine and Yarragadee using the standard VGOS equipment. We describe the experimental setup, signal chain and key developments enabling these observations. Furthermore, we report on the ongoing efforts in the fringe fitting phase with critical effects on the delay. This crucial development is a valuable opportunity to further develop VLBI observations to satellites in preparation for the GENESIS mission. In addition, such observations could realize the first-ever inter-technique ties between VLBI and GNSS in the Australian region.

How to cite: Schunck, D., McCallum, L., McCallum, J., and McCarthy, T.: Observing GNSS Satellites with the AuScope VLBI Array: A Testbed for the VLBI Component of the GENESIS Mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18387, https://doi.org/10.5194/egusphere-egu25-18387, 2025.

Realizing the terrestrial scale from Global Navigation Satellite System (GNSS) data requires precisely calibrated and highly stable satellite antenna phase centers. The results from the third International GNSS Service (IGS) reprocessing campaign, however, have raised renewed concerns about the long-term stability of the GNSS transmit antenna phase center relative to the spacecraft center of mass. Reevaluation of the satellite radial phase center offsets (z-PCOs) based on SINEX data from multiple IGS analysis centers revealed abrupt changes over time of up to 1 decimeter. Commonly cited reasons for time-varying z-PCO estimates are “aging” of the antenna and its radiation pattern, changing composition of the satellite constellation and ground network, and movement of the center of mass as propellant is consumed for satellite momentum dumps or orbital maneuvers. In this presentation, we shed light on another, yet unknown, effect arising from the drift of the satellite clock that prompts GNSS ground segment operators to adjust the clock frequency to ensure that the timing corrections in the satellite broadcast navigation message remain within the limits specified by the signal-in-space interface. The frequency adjustments are easily detectable in satellite clock bias estimates or broadcast clock correction parameters. However, this is only half the story; changing the clock frequency results in boresight angle-dependent lengthening or shortening of the carrier phase range, which the satellite antenna z-PCO parameter can almost perfectly absorb. As we will demonstrate through simulations and real-world examples from various GNSS spacecraft, a 4 × 10^-10 correction applied to the onboard clock fundamental frequency (10.23 MHz) alters the estimated satellite z-PCOs for the standard ionosphere-free linear combination of L1 and L2/E5 by approximately 7 cm. The results indicate that satellite clock adjustments are the cause of the observed z-PCO jumps in the IGS “repro3” time series.

How to cite: Dilssner, F., Springer, T., Gonzalez, F., Schönemann, E., and Gini, F.: The Ticking Truth: How Subtle Clock Adjustments Influence GNSS Satellite Antenna Offset Estimates, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19163, https://doi.org/10.5194/egusphere-egu25-19163, 2025.

The upcoming Genesis mission of the European Space Agency (ESA) will allow for the combination of all 4 space geodetic techniques, being GNSS (Global Navigation Satellite Systems), SLR (Satellite Laser Ranging), DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite), and VLBI (Very Long Baseline Interferometry). This promises progress for an improved terrestrial reference frame (TRF) and the determination of inherent biases of each technique. From the VLBI and VGOS (VLBI Global Observing System) point of view, the advantage of adding VLBI observations of satellites into an observing session is that it allows the ability to also estimate the geocenter and the satellite’s orbit to centimetre precision, as shown in previous studies. There is still an opportunity to investigate the effect of the chosen satellite orbit itself and the parameterisation in the analysis stage, on the determined Earth Orientation Parameters (EOP) and the potentially determined satellite orbit. In this work we show the simulation of VGOS observations of a Genesis-like satellite, including scheduling, observations simulation, and analysis. This research will address the impact on the determination of EOPs and the determined satellite orbit, by the chosen initial satellite orbit and the parametrisation in the analysis process. The results of this study will enable future VLBI schedule optimisation that include satellite observations, and serve as a reference for orbital elements selection for VLBI observed geodetic satellites.

How to cite: Wolfs, R. and Haas, R.: Simulating and analysing VGOS observations for Genesis orbits and EOP determination, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19542, https://doi.org/10.5194/egusphere-egu25-19542, 2025.

Further development of the Satellite Laser Ranging (SLR) technique is essential not only to achieve the goals defined by the Global Geodetic Observing System (GGOS) but also to meet the growing challenges associated with understanding the increasingly frequent and dynamic processes occurring at the Earth's surface. SLR plays a key role in the realization of the Terrestrial Reference Frames (TRFs). It is also crucial for determining the gravitational potential, as the C₂₀ and C₃₀ coefficients in solutions from dedicated GRACE Follow-On missions are replaced by those derived from laser observations.

This study investigates the optimal orbital parameters to consider for future geodetic satellites. We performed simulations for satellites with different inclination angles ranging from 0° to 180° with 1° interval, and at five different altitudes ranging from 1,500 km to 10,300 km with 1,200 km interval. The analysis was carried out under two different scenarios: (1) optimisation for TRF realisation and (2) optimisation for recovery of the Earth's gravitational potential. The results indicate that the optimal satellite altitude for TRF implementation is about 3,700 km, with inclination angles between 0°-20° or 160°-180°, which minimises formal errors in the determination of geocenter coordinates and Earth Rotation Parameters (ERP). On the other hand, geodetic satellites designed primarily to determine the parameters of the Earth's low gravity potential should operate at an altitude of 1,500 km with inclinations between 30°-40° or 135°-145°.

In particular, none of the current satellites in the SLR constellation have orbital parameters optimised for low-degree gravity recovery. Adding a single satellite with suitable inclination parameters to the existing constellation of ten geodetic satellites would reduce the error in the determination of the Earth's oblateness term, C₂₀, by order of magnitude.

How to cite: Najder, J., Sośnica, K., Zajdel, R., and Kur, T.: Simulation for SLR space segment development to improve global geodetic parameters - different inclination angles & altitudes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20752, https://doi.org/10.5194/egusphere-egu25-20752, 2025.

Obtaining consistent phase center corrections (PCCs) for GNSS receivers remains a significant challenge, as there is currently a lack of benchmarks to  consistently evaluate patterns or comparable values between different calibration institutions and methods (anechoic chamber and field robots). To address this problem, a global collaboration with nine calibration institutions known as the IGS Ring Calibration Campaign (IGS ringCalVal) has been  launched. This comprehensive initiative aims to compare results from different calibration methods and create a robust framework for quality assessment. Six antennas from different manufacturers were used for calibration in this campaign.

Over the past year, significant progress has been  made. We have developed benchmarks and methods that facilitate the comparison of PCC patterns. Our detailed results show that in the pattern domain, the system/frequency consistency per antenna design varies within an uncertainty level of ±1 mm, with an additional elevation-dependent effect. In the positioning domain, system-specific PPP (Precise Point Positioning) results per antenna and GNSS system are presented, which show a deviation of typically less than 2-3 mm for the horizontal coordinate component and less than 5 mm for the vertical component between different systems. But also, special cases will be discussed. Finally, these results are crucial for establishing global standards for PCC calibration and verification
of receiver antennas.

How to cite: Schön, S., Kersten, T., Bilich, A., and Sutyagin, I.: Collaboration in GNSS Antenna Calibration: Insights from the IGS Ring Calibration Campaign, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21229, https://doi.org/10.5194/egusphere-egu25-21229, 2025.

Geodetic applications depend on the precise transformation between terrestrial and celestial reference frames, which are tied by the Earth Orientation Parameters (EOP). Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable of observing the complete set of EOP, which includes polar motion, UT1-UTC, and celestial pole offsets. Over the past three to four years, India has been planning the establishment of a VLBI Global Observing System (VGOS) telescope. Thus, identifying the optimal location for these antennas is critical for enhancing the precision of EOP estimation. The International VLBI Service for Geodesy and Astrometry (IVS) conducts its VLBI observing program in two formats: 24-hr sessions and 1-hr sessions. While 24-hr sessions typically involve a global network of stations and measure the full set of EOP, the 1-hr sessions, called Intensive sessions, focus on determining UT1-UTC with a short latency and generally involve two to three stations.

This study uses VieSched++ software to simulate the optimal position of VGOS telescopes in the Indian subcontinent separately for both 24-hr and 1-hr sessions. For the 24-hr sessions, 14 potential VLBI stations, co-located with GPS stations, are selected and simulated in addition to three different reference networks. Additionally, the study assesses the significance of using station-specific tropospheric turbulence parameters and wind speed in finding the optimal position. For 1-hr sessions, simulations were conducted by varying the VGOS telescope’s location in India on a regular 5 × 5 degree grid. It investigates the change in the precision of different baseline solutions when a third station from India is added in both regular mode and tag-along mode. Furthermore, it also identifies a new baseline, which includes one Indian station and one other station, that could be part of future Intensive sessions. 

Our findings show that the southern and north-eastern regions of India are optimal for improving EOP precision from 24-hr and 1-hr VGOS observing sessions, respectively. The findings also highlight that while a station may be geometrically advantageous for 24-hr sessions, the location might not be favorable if the tropospheric turbulence value is too high.

How to cite: Laha, A., Schartner, M., Böhm, S., Krásná, H., Soja, B., Böhm, J., Balasubramanian, N., and Dikshit, O.: Optimal Placement of VGOS Telescope in India: Simulation Insights for 24-Hour and 1-Hour VLBI Sessions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-285, https://doi.org/10.5194/egusphere-egu25-285, 2025.

Effectively communicating geodesy’s role in advancing our understanding of the dynamic Earth system by quantifying our planet’s changes in space and time is crucial for raising public awareness and support for this essential science. To bridge knowledge gaps and engage diverse audiences, the International Association of Geodesy’s (IAG) Global Geodetic Observing System (GGOS) has implemented a range of outreach and education initiatives. These efforts are designed to demystify geodesy, making it accessible to both scientific and non-specialist audiences through visual media, multilingual content, and user-friendly online platforms.

A recent innovation is the development of geodesy-themed cartoons that introduce geodetic concepts, products, and observation techniques in an engaging and relatable format. These cartoons also highlight pressing societal issues, such as the impacts of climate change and tectonic movements, making geodesy approachable for audiences of all ages. This visual storytelling approach complements other GGOS outreach tools, including multilingual educational videos, a comprehensive geodetic information portal at www.ggos.org, and active social media engagement on platforms like YouTube, LinkedIn, and Twitter.

By showcasing these initiatives, we aim to gather feedback and ideas from the geodetic community to enhance ongoing and future outreach activities. Through these collaborative insights, we hope to make geodesy more visible and relevant to both scientific and public audiences, ultimately fostering a broader understanding of its vital role in monitoring Earth’s changes and challenges.

How to cite: Sehnal, M., Barzaghi, R., Angermann, D., and Sánchez, L.: Geodesy Cartoons - Engaging the Public through Visual Storytelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1164, https://doi.org/10.5194/egusphere-egu25-1164, 2025.

The vision of the International Association of Geodesy’s Global Geodetic Observing System (GGOS) is “Advancing our understanding of the dynamic Earth system by quantifying our planet’s changes in space and time.” This mission, as well as work toward the goals and objectives of the GGOS Strategic Plan, is partly supported by targeted engagement with external stakeholders, managed as a component of the GGOS Coordinating Office. GGOS External Relations includes a work portfolio that focuses on advocacy, visibility, and collaboration to ensure geodesy is a visible, valued, and sustainable worldwide asset.

Working toward proactive engagement with the broader Earth observations community, GGOS external outreach and engagement centers on advocacy for interoperable, discoverable, and openly available geospatial data; promoting infrastructure development; identifying geodetic contributions to United Nations frameworks, as well as working with external partners to leverage the use of geodesy in broader Earth Observations campaigns.

We present an update on how GGOS participation in diverse stakeholder organizations works to identify synergies, making connections across organizations in the name of geodesy and mutual benefit. How GGOS participation and leadership – often on behalf of the IAG – works to ensure Earth observation organizations are aware of their dependency on geodetic infrastructure for applications such as climate change and disaster risk reduction will be discussed.

Opportunities for the geodesy community to engage with and benefit from GGOS external relations activities will be presented.

How to cite: Craddock, A., Gross, R., Sehnal, M., Rodriguez, J., Angermann, D., Sánchez, L., and Peidou, A.: The Global Geodetic Observing System: Facilitating Opportunities for Strategic Outreach, Collaboration, and Engagement with External Stakeholders, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7520, https://doi.org/10.5194/egusphere-egu25-7520, 2025.

Over the past decade, the IVS has undertaken enormous efforts to modernize its infrastructure under the VGOS (VLBI global observing system) umbrella in order to meet the objectives set forth by GGOS. Key feature are smaller, faster antennas to facilitate a better sky coverage, equipped with broad-band receivers observing between 2-14 GHz to reach a better signal-to-noise ratio. Another innovation of VGOS are twin telescopes, i.e. two VGOS antennas at the same location, separated only by dozens of meters. Currently three pairs are deployed. And all VGOS antennas, with the exception of a small number, are co-located with a legacy antenna.

The results of the fist years of VGOS observations are unprecedented in their accuracy, especially in regards of the station positions. However, this now unveils previously unknown or unnoticed systematics, signals hidden by the noise, or signals which remained unmodeled as they were considered to small to rise to significance.

In this study, we focus on the station positions of VGOS antennas and their residuals, compare them to their twins, and to the respective legacy antennas. We discuss the impact and origin of until now unseen signals, and explore possible methods to model and/or mitigate them to reach the highest possible accuracy.

How to cite: Karbon, M., Azcue, E., Belda, S., Escapa, A., and Ferrandiz, J. M.: Exploration of VGOS station position estimates and the signals within, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8330, https://doi.org/10.5194/egusphere-egu25-8330, 2025.

The Global Geodetic Observing System (GGOS) or the International Association of Geodesy (IAG) is currently focusing on the definition of Essential Geodetic Variables (EGVs). Essential Variables (EVs) serve as basic metrics that encapsulate critical aspects of geodetic observations, products and results, ensuring a structured framework for observing, understanding and modelling the Earth system, and for providing the fundamental layer (i.e. geodetic reference frames) for National Administrations and sustainable development. Today, essential variables in geodesy are able to offer unprecedented opportunities to improve reliability, consistency and accuracy of geodetic measurements and products. These variables enable the scientific and policy-making communities to address pressing challenges such as monitoring sea level rise and climate change effects, understanding Earth dynamics, supporting disaster risk reduction, and facilitating reference infrastructure for sustainable development. By focusing on variables deemed 'essential', resources can be strategically allocated to maximise their impact on achieving specific objectives and ensure efficient data collection and use.

In addition, EGVs promote interdisciplinary cooperation and international standardisation, providing a common language and reference for geodetic research and applications. The definition and adoption of EGVs will facilitate that geodetic data remain robust, traceable and relevant to advance science, inform policy and support societal needs. Establishing a comprehensive and widely accepted catalogue of EGVs, accompanied by well-defined requirements and stewardship, is critical to realising these benefits and meeting the growing demands on geodetic science in a rapidly changing world.

The Global Climate Observing System (GCOS) was the first community to introduce the concept of EVs, the Essential Climate Variables (ECVs), which have been widely adopted by the scientific and policy communities. Subsequently, the Global Ocean Observing System (GOOS) defined a complementary set of Essential Ocean Variables (EOVs) with standards aligned with the ECVs. Similarly, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), a partner of the Biodiversity Observing Network of the Group on Earth Observations (GEO BON), has initiated the definition of Essential Biodiversity Variables (EBVs). There are currently other ongoing initiatives to introduce additional sets of EVs, not only to describe the Earth System, but also the socio-economic system, including for example urban development, energy and minerals, health, agriculture, etc. In this international and interdisciplinary context, this contribution presents the progress made by GGOS in defining a catalogue of essential geodetic variables that is fully consistent with the concept and the existing essential climate and ocean variables ECVs, EOVs.

How to cite: Sánchez, L., Gruber, T., and Angermann, D.: The Strategic Role of Essential Variables in Geodesy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8814, https://doi.org/10.5194/egusphere-egu25-8814, 2025.

Modern society is dependent on satellites. In many countries, satellite information is essential for economic growth, the operation of critical infrastructure, and is a cornerstone of national defence forces. For satellites to operate accurately and reliably, their ‘place in space’ and Earth’s ‘place in space’ need to be observed and analyzed constantly. This information is provided through the global geodesy supply chain. The global geodesy supply chain is the collection of ground observing stations, data centres, analysis centres and highly qualified experts who observe the Earth and convert these observations into geodetic products which are essential to communicate accurately and reliably with satellites. This presentation will describe the weaknesses in the global geodesy supply chain and explore the actions of Member States and partners to strengthen it as described in the First Joint Development Plan for Global Geodesy. Key activities for Member States include: strengthening national awareness and governance in geodesy, recognizing the global geodesy supply chain as national critical infrastructure and engaging in bilateral or multilateral agreements with other Member States.

How to cite: Brown, N. J.: Hidden Risks: The weakness in the global geodesy supply chain that threaten modern society, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9966, https://doi.org/10.5194/egusphere-egu25-9966, 2025.

In addition to extreme storm surges that can damage aquaculture cages, rapid temperature changes also pose a threat to aquaculture production. In this context, variations in either water mass pathways and/or local water mass properties can lead to sea temperature variations around aquaculture facilities. There are about 15 aquaculture facilities along the Valencian coast in the western Mediterranean, and many more along the rest of the Spanish Mediterranean coast. These facilities typically produce sea bream, croaker, sea bass and eel, among other species of commercial interest.

In this work, we use 35 years of daily averaged horizontal velocities from the Nemo reanalysis, freely accessible in Copernicus and with a horizontal resolution of about 4.2 km, to study variations in water mass properties (potential temperature, salinity) and/or water mass pathways over the Valencian coasts. First, we have performed an analysis of the ocean currents through a real-empirical orthogonal function approach. Next, we performed a Lagrangian analysis. To this end, we have advected horizontally massless particles forward and backward in time for a total of 6 months. The particles are deployed daily from 1988 to 2021 at model grid points off the Valencian coast. Horizontal advections are performed at 10 and 50 m depth, in order to capture any change near the typical depth of aquaculture cages (at about 20 m depth).

How to cite: Sayol, J.-M., Vigo, I., García-García, D., and Bordehore, C.: Study of the effects of water mass variations on aquaculture facilities off the Valencian coast, Spain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11753, https://doi.org/10.5194/egusphere-egu25-11753, 2025.

Ocean angular momentum (OAM), a measure of the rotational motion of the oceanic fluid masses, undergoes alterations as a consequence of changes in both the distribution of ocean mass and the direction and speed of ocean currents. While a number of products provide estimates of these changes, they rely on global ocean current models.

Geostrophic currents (GC) represent the dominant current patterns in the ocean, emerging from the equilibrium between the Coriolis force and the pressure gradient force. They play a pivotal role in shaping oceanic circulation patterns. With the advent of current satellite missions, it is now feasible to obtain geodetic estimates of GC using satellite data. By integrating Sea Surface Height (SSH) data from satellite altimetry, an independent geoid derived from satellite gravity data, and temperature and salinity profiles, GC can be estimated at various depths across the global ocean with a spatial resolution of 0.25° x 0.25°.

These estimates of GC are employed to calculate oceanic angular momentum (OAM). The OAM derived from satellite-based GC is then compared with a number of existing OAM products. This approach is anticipated to provide more reliable estimates, as the GC derived from satellite data align more closely with in-situ current measurements than model-based OAM calculations.

How to cite: Vargas Alemañy, J. A., Vigo Aguiar, I., José Manuel, F. L., and David, G. G.: Satellite-Based Geostrophic Currents for Improved Ocean Angular Momentum Estimates, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12811, https://doi.org/10.5194/egusphere-egu25-12811, 2025.

The International VLBI Service for Geodesy and Astrometry (IVS) is a globally operating service that coordinates and performs Very Long Baseline Interferometry (VLBI) activities through its constituent components, supporting geodetic and astrometric work on reference systems and Earth science research. The service consists of over 80 components, which are supported by about 40 organizations in more than 20 countries. It was established in 1999 as a service of the International Association of Geodesy (IAG) and was recognized as a service of the International Astronomical Union (IAU) a year later. The IVS interacts closely with the International Earth Rotation and Reference Systems Service (IERS), which is tasked by IAU and IUGG (International Union of Geodesy and Geophysics) with maintaining the international celestial and terrestrial reference frames (ICRF and ITRF) and providing Earth orientation parameters (EOP) required to study earth orientation variations and to transform between the ICRF and the ITRF. VLBI is one of the most accurate methods used to measure the Earth and its orientation in space. With the help of international networks of radio telescopes compact radio sources (typically quasars) are observed and their signals used to determine the radio source positions, the Earth orientation parameters, and the positions of the radio telescopes. IVS coordinates VLBI observing programs, sets performance standards for VLBI stations, establishes conventions for VLBI data formats and data products, issues recommendations for VLBI data analysis software, sets standards for VLBI analysis documentation, and institutes appropriate VLBI product delivery methods to ensure suitable product quality and timeliness. VLBI data products currently available are the full set of EOP, the TRF, the CRF, and tropospheric parameters. All VLBI data products are archived in IVS Data Centers and are publicly available. The IVS data set extends from 1979. We provide an overview of the status and current activities of the service.

How to cite: Haas, R. and Behrend, D.: International VLBI Service for Geodesy and Astrometry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13276, https://doi.org/10.5194/egusphere-egu25-13276, 2025.

Various features of the Earth system, including its shape, gravitational field, and orientation in space, can be measured through geodetic observations. These measurements play a vital role in both scientific research and practical applications, as evidenced by their contributions to the study of geodynamic events, climate change monitoring, and navigation in space and on Earth. Recognizing the importance of these characteristics, the Global Geodetic Observing System (GGOS) recently initiated the definition of Essential Geodetic Variables (EGVs). These variables represent core metrics that capture key geodetic properties of the Earth. Requirements for EGVs include accuracy, spatiotemporal resolution, and latency, with the latter being especially critical for real-time applications. To meet user needs, many scientific disciplines depend on forecasts of specific EGVs over varying time horizons.

The Space Geodesy Group at the University of Alicante, along with the Geodesy Group at Spain’s National Geographic Institute (IGN), possesses extensive expertise in geodesy, particularly in Earth rotation theory, modeling, and predicting Earth Orientation Parameters (EOPs). This expertise has been bolstered by their active participation in the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC), which ran from September 1, 2021, to December 31, 2022. These efforts have paved the way for establishing the first Spanish-Portuguese Geodetic Prediction Center, which will primarily focus on EOP forecasting. The center also aims to expand in the near future to include other critical geodetic products and EGVs, such as Earth angular momentum functions, station coordinates, tropospheric zenith wet delays, ionospheric total electron content, and satellite orbit predictions.

How to cite: Belda, S., Karbon, M., Guessoum, S., Del Nido, L. D., Modiri, S., Azcue, E., Rodríguez, J. C., Domingo Centeno, L. C., Moreira, M., Escapa, A., and Ferrándiz, J. M.: Progressing Toward the Establishment of a New Geodetic Prediction Center, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13935, https://doi.org/10.5194/egusphere-egu25-13935, 2025.

The International Laser Ranging Service (ILRS) provides Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) observations and data products with a focus on Earth and Lunar science and engineering applications. The basic observables are the precise two-way time-of-flight of ultra-short laser pulses from ground stations to retroreflector arrays on satellites and the Moon and the one-way time-of-flight (TOF) measurements to space-borne receivers (transponders). The ILRS network is experiencing significant growth, with multi-techniques Core Sites exploiting the combined strengths of the various geodetic techniques, new low-cost systems, some being transportable. Some of the stations are also dedicating some of their efforts to tracking Space Debris, contributing to the maintenance of various data catalogs, helping support operations and continue their contributions to geodetic science. New stations joining the network, and new satellite missions supported, are strengthening the ILRS contribution to the International Terrestrial Reference Frame (ITRF), and expanding the spectrum of satellite applications supported by the Service. Improvements in Satellite Laser Ranging science products continue, enabled by new data processing and analysis techniques and better modeling. Fundamental physics applications continue to be supported through dedicated campaigns, as are time-transfer experiments and Lunar Laser Ranging (LLR) applications, and the support of new lunar missions.

It is the goal of this presentation to report on progress achieved by the International Laser Ranging Service (ILRS) during the last five years.

How to cite: Carabajal, C. C., Pearlman, M., Husson, V., Merkowitz, S., Blossfeld, M., and Courde, C.: International Laser Ranging Service (ILRS) Status, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14088, https://doi.org/10.5194/egusphere-egu25-14088, 2025.

In the ocean, horizontal water fluxes can be estimated from a variety of in situ measurements and ocean general circulation models. However, the study of such fluxes with remote measurements has been elusive for decades. In recent years, a technique has been developed that allows the calculation of net ocean water transports between basins from: (1) temporal gravity measurements made by the GRACE and GRACE-FO missions; (2) global precipitation and evaporation such as those from the ERA5 atmospheric reanalysis model. In this work, we show a compilation of the results obtained with this technique, such as the net water exchange between ocean basins and between semi-enclosed seas (Black, Mediterranean and Baltic Seas, and the Arabian Gulf) and the open ocean. Such results are useful for understanding ocean dynamics and providing constraints for numerical ocean models.

How to cite: Garcia-Garcia, D., Boulahia, A. K., Trottini, M., Vargas‐Alemañy, J. A., Sayol, J., and Vigo, M. I.: Estimates of net horizontal water fluxes in the ocean from GRACE/GRACE-FO and ERA5, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15595, https://doi.org/10.5194/egusphere-egu25-15595, 2025.

This presentation highlights the advancements in the Red Atlántica de Estaciones Geodinámicas y Espaciales (RAEGE), a collaborative Spanish-Portuguese geodetic infrastructure. The project envisions four VGOS radio telescopes: two in Spain (Yebes and Gran Canaria) and two in Portugal (Santa Maria and Flores, Azores). All stations will be equipped with a fast-moving high-sentitivity VLBI radiotelescope and its associated 2-14 GHz VGOS receiver, GNSS receivers, gravimeters and a local-tie network. Additionally, Yebes station has a state-of-the-art Satellite Laser Ranging (SLR) system.

The RAEGE Yebes VGOS radiotelescope has been operational and a part of the VGOS core network since 2016. The RAEGE Santa Maria VGOS radiotelescope recently underwent extensive maintenance in 2021 and 2022, and high-temperature superconducting filters (HTS) to mitigate interference from space debris radar signals were installed in its VGOS receiver. Following these upgrades, it became part of the VGOS core network in October 2023.

Notably, the RAEGE Yebes SLR station completed the International Laser Ranging Service (ILRS) quarantine in October 2024 and is now fully operational within the ILRS framework.

Regarding RAEGE Gran Canaria station, the contracts for its construction were awarded in 2024, with civil works set to commence in early 2025.

Collectively, these developments underscore RAEGE's substantial contribution to global geodetic initiatives, aligning with UN resolution 69/266 and the objectives of the Global Geodetic Observing System (GGOS). This presentation will provide an overview of the current status and future plans for the RAEGE network, emphasizing its role in fostering international collaboration to address scientific and societal challenges.

How to cite: Lopez-Perez, J. A., Garcia-Castellano, A., Gonzalez-Garcia, J., Albo-Castaño, C., Magalhaes, L., Morales Comalat, F. J., and Lopez-Fernandez, J. A.: Current Progress of the RAEGE Project: A Spanish-Portuguese Collaboration in Geodesy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16476, https://doi.org/10.5194/egusphere-egu25-16476, 2025.

Around 70% of fish stocks worldwide are overfished. In European waters, this overfishing has forced EU authorities to drastically reduce fishing effort in European Mediterranean waters and to make changes in fishing gear (e.g. larger mesh sizes, or flying trawl doors). However, the new regulations do not mention the creation of marine reserves as one of the mandatory measures. According to our studies and the scientific literature, the design of a well-designed network of no-take marine reserves is an essential tool for stock recovery, the very measure on which the European Commission places the least emphasis. In order to establish marine protected areas, the ocean currents at a regional scale are a key element that allows us to understand how the planktonic stages drift between spawning to recruitment areas. We take into account a geodesic approach based on satellite observations and also combined with regional high-resolution 3D oceanographic circulation models.

We show that a well-designed network of marine reserves, taking into account variables such as the size of the protected area (which will depend on the target species or species), the spatial design of the network (based on the role of currents as a mechanism for dispersal of larval stages), the biology of the target species, among others. We address the optimisation of stock recovery through a meta-population, spatially-explicit and size-differentiated approach (important when quantifying the reproductive capacity of a population). Sub-stocks within the meta-stock would be connected by Lagrangian advection and current simulations using a combination of Ocean Parcels (https://oceanparcels.org/) and the IBI-MFC model freely available on Copernicus (https://marine.copernicus.eu/about/producers/ibi-mfc). This approach would allow the optimisation of the design of a ‘no take’ space network and help to recover the populations of exploited marine species in a faster and more efficient way.

How to cite: Bordehore, C., Sayol, J. M., Garcia-Garcia, D., Dobson, J. A., Fonfria, E. S., Vargas, J. A., and Vigo, I.: A proposal to recover fish stocks: a meta-population, size-differentiated model coupled with currents , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17638, https://doi.org/10.5194/egusphere-egu25-17638, 2025.

The geodetic community provides essential data, products and services that support critical sectors of our modern economies. Positioning, navigation, timing, infrastructure monitoring, natural hazard modelling and early warning systems, climate change science, are just a few examples of applications that depend on the existence of the so-called Global Geodesy Supply Chain (GGSC). The GGSC comprises the entire cycle of creation of geodetic products and their delivery to the users. It includes structural elements (e.g. ground and space assets, data centres, analysis and combination centres) and operational elements that support these functions (e.g. human resources, governance structures).

Since its establishment in 2023, the United Nations Global Geodetic Centre of Excellence has been working with the international geodetic community, national agencies and Member States to strengthen the GGSC. The strategic objectives of these efforts are outlined in the 1st Joint Development Plan for Global Geodesy. The expert evidence gathered by the UN-GGCE indicates weaknesses in the GGSC, which threatens socio-economic activities that rely on the supply of accurate, precise, stable and timely geodetic products.

In order to ascertain more quantitatively the fragility of the ground networks, we have conducted simulation studies focusing on what appear to be particularly concerning elements. Here we will discuss results for the Satellite Laser Ranging network, showing how the loss of relatively few stations can lead to significant degradation of the ILRS products and therefore to the combined global terrestrial reference frame. The lower quality of the global products obtained in the simulated scenarios would most obviously affect the scientific goals of the Global Geodetic Observing System, and its commitment to continuously monitor changes in the Earth system in an integrated manner. Likewise, operational applications dependent on a high-quality global terrestrial reference frame would also be affected.


* The findings, interpretations, and conclusions expressed herein are those of the author(s) and do not necessarily reflect the views of the United Nations or its officials or Member States.

How to cite: Rodríguez, J. C., Poshyvailo-Strube, L., and Brown, N.: How fragile is the global geodesy supply chain? A case study of the ILRS network., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19633, https://doi.org/10.5194/egusphere-egu25-19633, 2025.

Over the last decade, the International Astronomical Union (IAU) and the International Association of Geodesy (IAG) have organised successive Joint Working Groups (JWGs) to study in depth the current theories and models of Earth rotation, which are of paramount importance for general geodesy and astronomy, and for positioning and navigation on Earth and in space in particular. Their activities have resulted in IAU and IAG resolutions encouraging the improvement of such theories and models, particularly with regard to the consistency and accuracy of the Earth Orientation Parameters (EOPs). In this communication, we recall some results of the past JWGs and introduce the new JWG on Consistent Improvement of Earth Rotation Theory (CIERT) and its planned activities.

The former IAU/IAG JWG on Improving Theories and Models of Earth Rotation (ITMER) showed that the unexplained variance of the precession/nutation (PN) variables, measured in terms of the WRMS of the observed celestial pole offsets (CPO), can be significantly reduced by fitting to the observations some corrections of the linear component of precession and of the theoretical amplitudes of some lunisolar and planetary nutation terms. Furthermore, the unexplained WRMS is reduced to less than 3 mm by supplementing the corrections with appropriate Free Core Nutation (FCN) models. However, not only because of the need to deepen theoretical knowledge, but also because of the large number of nutation frequencies involved and the consequent limitations of the fits, the use of semi-empirical nutation models is only a temporary solution.

It is therefore necessary, and a major goal of the new JWG, to derive complete theories that bring together the many advances made by different research groups in recent years in a way that is internally consistent and also coherent with the analysis of observational data. One of the most recent advances is the derivation of fully analytical corrections to planetary nutations, which are competitive since they allow the empirical fit to be limited to the lunisolar terms.

Acknowledgment. This research was supported partially by Spanish Projects PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033); SEJIGENT/2021/001, funded by Generalitat Valenciana; and the European Union—NextGenerationEU (ZAMBRANO 21-04).

How to cite: Ferrándiz, J. M., Huang, C., Escapa, A., and Karbon, M.: On IAU and IAG collaboration in the new JWG on Consistent Improvement of Earth Rotation Theory, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19790, https://doi.org/10.5194/egusphere-egu25-19790, 2025.

Trustworthy, reproducible and open science requires the digital availability of well-documented, findable, accessible, interoperable and reusable data. Due to the high relevance of geodetic data beyond the geodesy (e.g., in geophysics, hydrology, oceanography, glaciology and climatology), it is essential to provide them in citable form that allow the provision of proper credit and attribution for the data producers and their institutions.

The assignment of digital object identifier (DOI) can provide such credit and additionally support data discovery in the internet. The registration of a DOI requires the provision of at least a minimum set of descriptive metadata in machine-readable form (following international standards) that complements disciplinary, contextual metadata and documentation. The objects assigned with DOIs are persistently archived at research data repositories and are fully citable in scholarly literature.

Since 2019, the GGOS Committee on DOIs for geodetic data is developing recommendations and guidance for the consistent use of DOIs for geodetic data across all services of the International Association for Geodesy (IAG). While the first version of metadata recommendation was developed for GNSS data, many general remarks are valid for data from other techniques.

Once the DOIs are registered, it is important to ensure that the data assigned with DOI are properly cited. This is an especially large challenge for geodetic data due to their high granularity and international character. It is common practice to provide data products representing different processing levels (e.g., ultra-rapid, rapid, final products) or products representing different levels of aggregation (e.g., solutions measured by stations are combined by regional analyses centers, the latter are later combined to one global best-fit solution that represents the final solution for one geodetic service). Only the citation of each object contributes to a combination product ensures that credit is given to all researchers and institutions involved. The challenge has different facets of which the technical implementation seems to be the smallest (the DataCite Metadata Schema has dedicated metadata properties to make digital connection between data, software and scholarly literature). Larger challenges lie in the practical citation of hundreds of DOIs in research articles (most journals do not accept it) or data publications and the more educational task to enable researchers to properly cite the data they used.

How to cite: Elger, K. and the GGOS Committee on DOIs for Geodetic Data Sets: Using DOIs for Geodesy – best practices and ongoing discussions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20004, https://doi.org/10.5194/egusphere-egu25-20004, 2025.

The European Plate Observing System (EPOS) facilitates access to GNSS data and derived products through its GNSS Thematic Core Service (TCS), harmonizing data availability from European networks. Rigorous quality control of RINEX files with GNSS measurements ensures the integrity of the raw data, ensuring reliability for subsequent processing and analysis. By implementing FAIR (Findable, Accessible, Interoperable, Reusable) principles, EPOS-GNSS enhances accessibility and supports advanced geodetic research and Earth system monitoring.

A central feature of EPOS-GNSS is GLASS, which supports the dissemination of GNSS data and derived products, including time-series, velocity fields, and strain rate maps. GLASS facilitates seamless access to these resources, utilizing international standards for data compatibility and interoperability. Although the data and products are distributed across different nodes and repositories, GLASS ensures a unified interface for users through the dedicated EPOS-GNSS portals or the EPOS Platform.

We will present the latest developments in the implementation and operation of EPOS-GNSS services, which are contributing for the scientific community to address key scientific and societal challenges, such as monitoring Solid Earth processes, while also supporting other scientific and technical applications. By streamlining access to comprehensive GNSS datasets and derived products, EPOS-GNSS enhances research capacity and fosters innovation in geodetic studies across Europe.

This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025 and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020).

How to cite: Fernandes, R., Bruyninx, C., Carvalho, L., Crocker, P., Janex, G., Legrand, J., Menut, J.-L., Socquet, A., and Vergnolle, M.: Integrating GNSS Data Across Europe: Advancing Geodetic Research and Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20655, https://doi.org/10.5194/egusphere-egu25-20655, 2025.

To realize the various benefits brought by Low Earth Orbit (LEO) satellites in single-receiver high-precision GNSS-based Positioning Navigation and Timing (PNT) services, LEO satellite orbits and clocks need to be processed and delivered to users in real-time with precision of a few centimeters. While post-processing of cm-level LEO satellite orbits and clocks can be widely achieved, real-time processing faces various Challenges. When the number of LEO satellites increases, the observation data downlinked to the processing center may experience large and complicated discontinuities and incompleteness depending on the downlinking strategies. Even with the observations downlinked in real-time, the LEO satellite clock precision tends to be very sensitive to the continuity and quality of the GNSS real-time products. This study first introduces the procedure for ground-based cm-level real-time LEO satellite Precise Orbit Determination (POD), including near-real-time POD, short-term prediction, and ephemeris fitting/broadcasting. Next, the short-term predicted orbits and long-term predicted clocks of LEO satellites are introduced and properly constrained in filter-based real-time LEO satellite clock determination to achieve a precision of about 0.2 ns. Strategies to deal with sub-optimal observation data and GNSS products are explained. With the proposed methods, a Signal-In-Space Ranging Error at sub-dm to 1 dm can be achieved in practice. 

How to cite: Wang, K., Xie, W., Chen, B., Liu, J., Wu, M., El-Mowafy, A., and Yang, X.: Real-time LEO satellite precise orbit and clock determination for augmenting GNSS: Strategies and Challenges, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2002, https://doi.org/10.5194/egusphere-egu25-2002, 2025.

Multipath continues to pose a significant challenge for the Global Navigation Satellite System (GNSS) technique in achieving precise Precise Point Positioning (PPP). Sidereal Filtering (SF) and multipath hemispherical map (MHM) represent common methods for mitigating multipath by leveraging satellite temporal and spatial repeatability. However, the effectiveness of these approaches relies heavily on the quality of the multipath correction model derived from preceding PPP residuals, which often contains product and parameter estimation errors. These errors can notably compromise the accuracy and reliability of multipath mitigation efforts. We propose an innovative method for extracting multipath based on a refined error separation strategy and mitigating multipath with SF. This method involves decomposing PPP residuals into multiple reconstructed components (RCs) using the multi-channel singular spectrum analysis (MSSA) technique and subsequently isolating multipath by reconstructing RCs exhibiting strong temporal repeatability. Extensive experiments with a 28-day dataset from 20 multi-GNSS stations demonstrated the effectiveness of our method. Compared to the conventional wavelet-based SF method, the proposed approach improved PPP accuracy by 23%, 20%, and 18% in the East, North, and Up directions, respectively, and by 18%, 16%, and 15% compared to the MHM method. Results also reveal that PPP residuals can be decomposed into multipath, high-frequency noise, common-mode error (CME), and site-specific errors. The last two components, which are non-repeatable in time and space, pose limitations on the effectiveness of conventional SF and MHM strategies in addressing multipath effects. 

How to cite: Li, X., Wang, L., Ding, X., Zhang, Q., Qu, X., and Shu, B.: New Insights of Accurate Multipath Mitigation for Multi-GNSS PPP Using Refined Multipath Extraction Strategy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2304, https://doi.org/10.5194/egusphere-egu25-2304, 2025.

Despite the increasing number of satellites in multi-constellation GNSS, signal availability and quality remain significant problems in urban and forested environments. Field obstacles such as buildings and dense vegetation can lead to severe multipath issues. Various methods have been developed to mitigate multipath effects on measurement results, including optimizing antenna placement, selecting appropriate antenna and receiver types, and employing advanced post-processing techniques. However, these efforts have been unable to completely eliminate multipath interference, which can greatly affect positioning accuracy. The authors of this presentation have developed a tool that helps identify and remove reflected signals from measurement data sets. This tool, called GNSS MPD, was developed to predict satellite signal obstructions. It considers Line of Sight (LOS) vectors between specific locations and satellite positions and obstacle models derived from airborne LiDAR data. The LiDAR data is automatically acquired from geoportal.gov.pl, enabling the generation of an approximate terrain cover model. Satellite obstructions are validated using a ray-casting method. As part of testing the developed platform, the authors designed two experiments. The first experiment is a comparative analysis between satellite visibility scenarios obtained from GNSS MPD calculations and hemispherical photography. The second study involves performing positioning using information regarding the satellite visibility from GNSS MPD software. As part of this study, five 24-hour measurement sessions were conducted in a highly urbanized area.  Based on the receiver's approximate position, satellite visibility scenarios are generated using the developed platform. Static positioning measurements were performed in the experiment, yielding two sets of results: one based on raw receiver observations and the other incorporating visibility scenarios from the platform to adjust the observation files. The test results demonstrate improvements in both accuracy and the success rate of position determination.

How to cite: Tomaszewski, D., Rapiński, J., Janowski, A., and Pelc-Mieczkowska, R.: Enhancing GNSS Positioning Accuracy in Challenging Environments: Development and Validation of a Multipath Prediction Tool, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2818, https://doi.org/10.5194/egusphere-egu25-2818, 2025.

How to cite: Steigenberger, P., Thoelert, S., and Montenbruck, O.: Evaluation of Galileo FOC Reference Antenna Patterns, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4275, https://doi.org/10.5194/egusphere-egu25-4275, 2025.

PRIDE PPP-AR is a Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) software specifically designed for applications in Earth sciences. Since its initial release in 2019, the software has been updated to version 3.1. The core strength of PRIDE PPP-AR lies in its PPP-AR processing capabilities with arbitrary dual-frequency ionosphere-free combinations. It is also featured by low Earth orbit satellite solutions, multipath mitigation, epoch-by-epoch constraints in segmented processing mode, multi-day continuous processing, and ocean tide loading corrections without ocean tide coefficients. Furthermore, PRIDE PPP-AR is compatible with the three major operating systems: Linux, Windows, and macOS, providing great convenience for early-career researchers, facilitating easier learning and usage.

Tests conducted using 511 IGS reference stations in January 2018 showed that, when compared with IGS solutions, PRIDE PPP-AR can achieve millimeter-level static solutions and tropospheric delays, and centimeter-level dynamic solutions, with an average fix rate of 95%. In the fields of geodesy and Earth sciences, the high-precision positioning capabilities of PRIDE PPP-AR make it a powerful tool for studying Earth dynamics, crustal deformation, and seismic monitoring. Additionally, its performance on high-dynamic platforms such as aerial photogrammetry and shipborne gravimetry is outstanding, providing technical support for scientific research and engineering practices in related fields. The new version of PRIDE PPP-AR will be able to fully utilize the advantages of GNSS modernization, enhancing high-precision positioning accuracy in a broader range of research areas.

How to cite: Geng, J. and Wen, Q.: PRIDE PPP-AR: mitigating multipath and day-boundary discontinuities for geodesy and geophysics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4789, https://doi.org/10.5194/egusphere-egu25-4789, 2025.

Tropospheric delay and multipath effect are two key errors that are difficult to be accurately corrected in Global Navigation Satellite System (GNSS) Precise Point Positioning Ambiguity Resolution (PPP-AR). The tropospheric residuals due to imperfect modeling can be significant in harsh environments, like in regions with complex terrain and during extreme weather. As the tropospheric delay and multipath effect are coupled in the unmodeled errors, the tropospheric residuals could be misunderstood as multipath. Therefore, accurate correction of the tropospheric delay is crucial for estimating the multipath. However, the coupling effect was not properly considered in previous studies. We propose a refined joint troposphere-multipath hemispherical map (TMM), by constructing a refined troposphere hemispherical map (THM) and an improved multipath hemispherical map (C-TMHM). We use ray-tracing and meteorological data to construct THM correction tables, while tropospheric delays in PPP-AR are corrected by retrieving the corresponding satellite tropospheric delay estimates to obtain "cleaner" multipath model values. Results show that the tropospheric THM model reduces GNSS residuals from about 10 mm to 2 mm at low-elevation (7°~30°) compared to the Vienna Mapping Functions 3 (VMF3). Because that the topographic complexity and the rapid variations in atmospheric water vapor are not adequately considered by simply using the elevation-dependent mapping function and horizontal gradients. In particular, part of the tropospheric residuals in the low-elevation are likely to be misinterpreted as multipath. Compared with multi-GNSS PPP-AR performance using traditional model (VMF3 and uncorrected multipath), the proposed TMM (THM and C-TMHM) model improves the positioning accuracy by 32.12% and 36.18% under the cases of complex terrain and extreme weather, respectively, while shortens the convergence time by 33.04% and 30.7%.

How to cite: Lu, R., Zhang, M., Li, Z., Yuan, P., and Jiang, W.: Improved multi-GNSS PPP-AR performance through refined tropospheric and multipath models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5095, https://doi.org/10.5194/egusphere-egu25-5095, 2025.

Global Satellite Navigation System (GNSS) has been widely used in our daily life, due to its high-precision positioning ability. However, in urban environments, GNSS signals are prone to obstructions from tall buildings, leading to Non-Line-of-Sight (NLOS) errors and a significant decline in positioning accuracy. Machine learning (ML) techniques for NLOS detection has emerged as a significant research hotspot, thanks to its advantages, such as requiring no hardware modifications, achieving high accuracy, and offering practical applicability, etc. However, the existing research on ML-based NLOS detection usually relies on single models, which are prone to becoming trapped in local optima during the optimization process. To overcome this limitation, we propose a GNSS NLOS detection method based on the Stacking Ensemble Learning (SEL) model. Initially, the fisheye camera is utilized to generate NLOS labels, and five GNSS signal features are extracted: elevation angle, carrier-to-noise ratio (C/N₀), measurement residual, C/N₀ rate of change, and pseudorange standard deviation. Subsequently, the SEL model is designed with a two-layer structure. The first layer consists of basic ML classification models, including Convolutional Neural Network (CNN), Gradient Boosting Decision Tree (GBDT), Random Forest (RF), and Support Vector Machine (SVM). The second layer employs Logistic Regression (LR) as the meta-learning model to integrate the outputs from the first layer. Finally, the trained SEL model processes the five GNSS signal features in real time for detecting smartphone GNSS NLOS signals, and incorporates a weighted model for SPP positioning. Several smartphone-based vehicle experiments were conducted in different urban areas of Wuhan, China, to validate the effectiveness of the proposed method. Experimental results demonstrate that the SEL method achieves GNSS NLOS detection accuracies exceeding 90%, with detection performance improvements ranging from 15.6% to 32.7%, compared with the single ML methods such as CNN, GBDT, RF, and SVM. Furthermore, the SEL method enhances 3D positioning accuracy, with improvements ranging from 26.7% to 39.6%. Particularly, in dense urban canyon areas, the vertical positioning accuracy is improved by up to 73.1%, effectively mitigating the impact of NLOS signals. This method requires no additional improvements to low-cost receiver hardware, thus offers potential for widespread application across various GNSS terminals, and provides new ideas for navigation and positioning in smart cities.

How to cite: liu, L., li, Z., and jiang, W.: An Enhanced Method for NLOS Signal Detection in Urban Environments based on Stacking Ensemble Learning for Smartphone Positioning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5389, https://doi.org/10.5194/egusphere-egu25-5389, 2025.

Since early 2023, the Galileo High Accuracy Service (HAS) has been officially providing free corrections for Precise Point Positioning (PPP). The HAS is structured into two service levels. The first level (SL1), currently available worldwide, delivers orbit and clock corrections along with code biases for three GPS frequencies (L1, L2C, L5) and four Galileo frequencies (E1, E5a, E5b, E6). The second level (SL2), which is planned to operate exclusively within the European Coverage Area (ECA), will include atmospheric corrections.

In January 2023, the Service Definition Document (SDD) established the targeted HAS accuracy at 15 centimeters horizontally and 20 centimeters vertically, with a confidence level of 68% for static users outside the Pacific region.

An initial evaluation of the HAS performance was conducted between Day of Year (DOY) 92 and DOY 153 of 2023. In terms of correction availability, the service supports an average of 16 to 21 corrected satellites (GPS and Galileo together), depending on the user’s location. Regarding accuracy, the corrections improved the Signal-In-Space Range Error (SISRE) by 54% for Galileo and 61% for GPS, when compared to broadcast ephemeris.

To validate the HAS corrections, Precise Point Positioning (PPP) was performed using data from 132 Regional Reference Frame Sub-Commission for Europe (EUREF) stations across Europe. The analysis was conducted in static mode with a dual-constellation configuration (GPS/Galileo), a 30-second sampling interval, float ambiguities, and uncombined measurements. The results achieved a 68% accuracy of 4.4 centimeters horizontally and 4.7 centimeters vertically.

These EUREF stations were subsequently employed to generate atmospheric corrections, specifically ionospheric and tropospheric, to test the second service level. Three station networks with varying densities were constructed, consisting of 132, 49, or 34 stations. After an evaluation of these atmospheric corrections coming from these networks, a PPP positioning over 64 other EUREF stations has been performed. This positioning was carried out in kinematic mode, using the same dual-constellation setup, 30-second sampling, float ambiguities, and uncombined measurements.

The results demonstrated that atmospheric corrections had a significant impact on positioning performance. The 68% accuracy improved by 43% horizontally and 47% vertically. Furthermore, the horizontal convergence time was reduced by half and is achieved in 60 minutes instead of 127 minutes. It highlights the potential benefits of the second service level for real-time applications.

ACKNOWLEDGEMENTS

 We would like to acknowledge Munich Aerospace for the scholarship that made this study possible.

REFERENCES

[1] EUSPA, “Galileo high accuracy service service definition document (HAS SDD),” European Union, Tech. Rep., 2022.

How to cite: Parra, C., Hugentobler, U., Pany, T., and Baumann, S.: Performance Assessment of Galileo High Accuracy Service for PPP and Atmospheric Correction Impact in 2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6826, https://doi.org/10.5194/egusphere-egu25-6826, 2025.

The BDS-3 provides signals at six different frequency bands, which are expected to improve the precision and convergence speed of Precise Point Positioning (PPP). To fully utilize the full-frequency data from BDS-3, three PPP function models were constructed: the six-frequency undifferenced and non-combined model (UC6), the single-layer six-frequency ionosphere-free model (IF6-1), and the six-frequency ionosphere-free dual-combination model (IF6-2).For the six-frequency undifferenced and non-combined model (UC6), the IFB (Inter-frequency Bias) processing strategy was studied, and the impact of three commonly used processing strategies on IFB estimation was analyzed. The results showed that when using constant models and random walk models, the estimated IFB values were similar, while the white noise model, despite slight fluctuations in the estimated IFB, exhibited a trend consistent with the other two models.The positioning experimental results indicated that the positioning accuracy after static convergence for the UC6, IF6-1, and IF6-2 models was similar. The horizontal mean accuracy was 1.36, 1.35, and 1.39 cm, respectively, and the vertical accuracy was 1.42, 1.45, and 1.63 cm. In dynamic mode, the horizontal accuracy was 4.04, 4.10, and 4.12 cm, and the vertical accuracy was 5.52 cm, 5.19 cm, and 5.02 cm.In terms of convergence time, the IF6-1 model showed superior static and dynamic convergence performance compared to the UC6 and IF6-2 models. Further analysis compared the receiver clock offsets, inter-frequency biases, and zenith wet delays between the different models. The receiver clock offset time series from all three models were consistent, and the inter-frequency bias for the same receiver model remained stable throughout the day. Additionally, the zenith wet delay estimates from all three models tended to converge after the process reached steady-state.

How to cite: Wang, L., Ma, C., Cui, B., Huang, G., and Zhang, Q.: Performance Analysis and Comparison of BDS-3 All-frequency Precise Point Positioning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8092, https://doi.org/10.5194/egusphere-egu25-8092, 2025.

After Google’s release of Android Nougat (Android 7) in 2016, raw GNSS observations of Android smartphones have been freely accessible to the GNSS research community. Using smartphone raw GNSS measurements, numerous theories and practical methods were developed to achieve high precision in positioning, navigation, timing, and GNSS remote sensing. However, due to the chipset and built-in antenna quality, smartphone observations have more powerful noises compared to the geodetic grade GNSS receivers. Besides, frequent interruptions and cycle slips are present in smartphone observations. Therefore, it is difficult to achieve high positioning accuracy with smartphones, since it requires more sophisticated data processing methods. Smartphone stochastic modeling can be included in these methods since the variation of observation noise follows behaviors that are difficult to represent as a function of satellite elevation angle, while carrier-to-noise ratio (C/N0) representation provides a more suitable weighting scheme e.g., for smartphone Precise Point Positioning (PPP).
In addition to the current developments, analyzing the time-correlation behavior of smartphone observation noise can help to develop resilient algorithms for positioning, such as the detection of cycle slips, outliers, and adaptive filtering methods. In this contribution, we present noise analysis of smartphone raw GNSS measurements from different perspectives, namely stand-alone, double-differenced, and based on PPP residuals. To eliminate systematic effects such as the multipath effect from smartphone observations, we use a Kalman Filter algorithm and we compare it with Least Squares Harmonic Estimation (LS-HE). To investigate the time-correlation property of filtered observations, we use autocorrelation and Allan Deviation (AD) methods. Results showed that even if the strong periodicities of the multipath effect are filtered, there are residual multipath effects that remain in smartphone observations and residuals. Furthermore, AD analysis showed that smartphone observations/residuals contain white noise and time-correlated noise that exhibits similar characteristics to a Gauss–Markov process. Using these insights, our study discusses the influence of the weighting scheme and time-correlated errors on smartphone PPP and recently developed adaptive filtering techniques with the goal of improving PPP performance. We aim to provide a foundation for further advancements in modeling and mitigating multipath and time-correlated smartphone observation noises.

How to cite: Gul, C. and Warnant, R.: Stand-alone, double differenced, and residual-based noise analysis of smartphone raw GNSS observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8500, https://doi.org/10.5194/egusphere-egu25-8500, 2025.

In precise point positioning, the fixed ambiguity can significantly improve the positioning accuracy of PPP and accelerate the convergence speed to a certain extent. The quality of phase deviation products directly determines the ambiguity resolution effect, and then affects the positioning performance of PPP-AR. At present, CNES is the only analysis center that publicly provides real-time observable-specific signal bias products (OSB). In order to promote the practical application of RT PPP-AR, it is necessary to evaluate the data quality and PPP-AR positioning performance of real-time OSB products provided by CNES. In this paper, the observation data of 42 MGEX stations from May 1, 2023 (DOY 121) to May 10, 2023 (DOY 130) are selected, and the positioning performance of PPP-AR is analyzed and evaluated after OSB product correction. In terms of OSB product quality, the data availability (DA) of GPS satellite is greater than 94%, that of Galileo satellite is less than 56%, and the standard deviations (STD) of GPS and Galileo satellite are 0.053 and 0.075, 0.031 and 0.044 respectively. After correction by OSB products, the percentage of wide lane (WL) residuals of GPS and Galileo systems exceeds 90% and 83% within 0.25 cycle, and the percentage of narrow lane (NL) residuals of the two systems within 0.25 cycle is 83% and 81% respectively. As far as the positioning performance of PPP-AR is concerned, the positioning errors of GPS+Galileo dynamic PPP-AR in E, N and U directions are 1.45 cm, 1.51 cm and 4.16cm, respectively, and the ambiguity fixing rate is about 97%. Compared with PPP, the convergence time of PPP-AR corrected by OSB products can be shortened by more than 59%. However, due to the lack of phase deviation, there is a phenomenon of re-convergence in the positioning process. In this paper, Grey model is used to predict OSB data, which has certain reliability and significantly improves the situation of re-convergence.

How to cite: Huang, G., Yang, N., and Wang, L.: Performance analysis of undifferenced and uncombined PPP based on CNES OSB products, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9469, https://doi.org/10.5194/egusphere-egu25-9469, 2025.

This research involved an analysis aimed at determining the accuracy of results derived from the Trimble RTX web-based post-processing service for Multi-GNSS solutions. To achieve this, nine stations situated on the Eurasian plate were selected from the MGEX network set up by the IGS. A GNSS dataset from 2022 was processed using Trimble RTX. The data from these GNSS stations were analyzed as three satellite combinations: GPS-only, GPS-GLONASS, and GPS-GLONASS-Galileo.

Initially, a 3D transformation was applied to investigate statistically significant differences among the 24-hour processing results for the three combinations. Upon confirming that the differences in coordinates were statistically insignificant, the GNSS data was divided into two 12-hour datasets and three 8-hour datasets, which were then processed using Trimble RTX. The results from the 24-hour analysis were accepted as accurate for all three satellite combinations, and the differences between the 12-hour and 8-hour processing results were examined. The results indicated that, while the differences in coordinate components were insignificant, the use of all three satellite combination datasets contributed to both the Cartesian coordinate components and the standard deviation values.

How to cite: Oz Demir, D.: Statistical Analysis of Trimble RTX Service Processing Results, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9510, https://doi.org/10.5194/egusphere-egu25-9510, 2025.

GNSS campaigns are still in use today especially for the monitoring of natural hazards such as landslides and local subsidence. Studying the velocity uncertainty of GNSS campaign deformation monitoring is a challenge among scientists cause the velocity error cannot always be characterized as pure white noise.  We test the velocity uncertainty of GNSS campaign measurements referring to the mathematical theory developed to find the velocity uncertainty of GNSS continuous coordinate time series. GPS coordinate time series have been downloaded from the archive of NASA JPL. The time series have been decimated to annual synthetic GNSS campaigns because researchers usually can handle GNSS campaigns once every year in three or more consecutive days. Using the continuous GNSS coordinate campaigns we estimated the spectral indices for the 30 IGS stations spread across the globe. Then using these spectral indices and the formulation given in Zhang et al.1997, Mao et al. 1999, Dixon et al. 2000, and Williams 2003 we have developed a practical methodology to estimate noise amplitudes and velocity errors for the data of synthetically derived annual GNSS campaigns. The methodology avoids large matrix computations and consumes only a little PC memory. The velocity error derived using the above-mentioned approach has been cross validated by the velocity error derived from the sample of annual GPS campaign time series constituted employing the continuous GPS time series. 10-12 synthetically derived independent GPS annual campaign time series were formed from the continuous data of each of the thirty stations we used from the IGS network. Then the velocity error has been computed as the inter-quartile range of the velocities derived from those of the annually sampled time series. The inter-quartile range values are comparable with the velocity errors computed using the methodology described in this study. The significancy of the differences were also tested referring to Wilcoxon's Signed Rank hypothesis testing.  The method has been found to be promising for the velocity error estimation of GNSS campaign measurements.

How to cite: Sanli, D. U., Ercoban, M., Aras, M. C., and Uysal, E.: A practical methodology to scale velocity uncertainties derived from GNSS campaign time series, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9699, https://doi.org/10.5194/egusphere-egu25-9699, 2025.

Positioning, Navigation, and Timing (PNT) services have delivered significant benefits to modern society. Currently, much of our PNT needs are fulfilled by Global Navigation Satellite Systems (GNSS). However, GNSS is facing a series of challenges, including signal blockage in dense urban areas, bush land and indoors and susceptivity to radio frequency interference. There is a urgent global demand for backup solutions to address the reliability of GNSS. The substantial expansion and massive deployment of small satellites have catalyzed the development of Low Earth Orbit (LEO) communication constellations have been rapidly developed, such as SpaceX’s Starlink and China Satellite Network communication system. In the near future, these constellations are projected to comprise tens of thousands of satellites. These satellites present significant advantages over GNSS, such as operating at higher frequencies (over 10 GHz) and providing wider signal bandwidths (several hundred MHz), along with superior signal quality. Such attributes make them viable candidates for PNT solutions and open up opportunities to utilize their signals as alternative sources for PNT applications.

Due to unknown structure of commercial LEO communication signals, most positioning methods based on LEO communication satellites rely on Doppler measurements. However, Doppler-based positioning is challenging for high-dynamic objects and high-precision positioning, as it requires integrating over significant periods for range difference measurements and imposing height constraints. Previous experience suggests that positioning with ranging measurements significantly outperforms Doppler-based methods in terms of accuracy and applicability. Unlike GNSS, which has publicly available signal structures for obtaining range, LEO communication signal structures are not disclosed. Therefore, this study aims to develop algorithms for estimating ranging measurements derived from LEO communication signals with unknown signal structures.

The downlink signals of LEO communication systems (i.e. Starlink) are simulated. By employing the Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS) sequences as ranging sequences, we facilitate the coarse acquisition of communication satellites. Then, a Delay Lock Loop (DLL) is developed to track the PSS and SSS sequences to continuously estimate signal delays. Additionally, we exploit the benefits of Orthogonal Frequency-Division Multiplexing (OFDM) modulation in LEO communication signals by designing the multiple Phase Lock Loops (PLLs) to track various subcarriers. By applying the phase difference across different frequencies, we can construct artificial wavelengths at the meter level, akin to wide-lane combinations in GNSS. This approach can reduce the ambiguity in the integer number of wavelengths between the satellite and the receiver, which is a notable challenge in carrier measurements of high-frequency LEO communication signals. This study introduces two ranging schemes: one based on time delay estimation via synchronization sequences and the other on carrier phase tracking using multiple PLL. When combined with two-line element (TLE) files, these schemes enable a positioning service based on LEO communication satellites.

How to cite: ding, M., chen, W., wang, J., yang, Y., mi, X., and luo, H.: Range estimation method of LEO communication opportunity signals for alternative PNT , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9788, https://doi.org/10.5194/egusphere-egu25-9788, 2025.

The study of signatures in the ionospheric total electron content (TEC) related to seismic events such as earthquakes and tsunamis, has predominantly focused on significant, high-impact occurences, such as the 2004 Sumatra earthquake and tsunami (Mw 9.2) [2] or the 2011 Tohoku-Oki event (Mw 9.0) [3]. These generate clear signatures in TEC time series, that can offer valuable insights in enhancing early warning systems for tsunamis. However, despite the knowledge gained from these significant events, there remains a crucial gap in the literature concerning smaller-scale seismic events presenting Mw7 and few meters high tsunami waves. Indeed, while earthquakes with Mw around 7 are not considered small in a general sense, they are relatively minor in terms of their ability to generate pronounced ionospheric perturbations. Nevertheless, their study is equally important due to their potential for significant impact on humans and the environment. This has been demonstrated in seismic regions like the Mediterranean Sea, where the tsunami waves are amplified by narrow straits and coastal configurations, making even smaller events highly destructive. This underscores the critical need for studies focused on smaller yet impactful events to improve real-time tsunami early warning systems. 

Motivated by the seismic nature of the Mediterranean region, marked by small-scale earthquakes and tsunamis from a ionospheric point of view,we carried out the study related to the detection of the small signatures generated in the ionosphere by the Samos earthquake and tsunami that occurred on 30 October2020 (Mw 7.0), causing tsunami waves up to 3 m. This study examines Global Navigation Satellite System (GNSS) data to analyze the resulting ionospheric disturbances in total electron content (TEC) measurements. We detected TEC variations of up to 0.3 TECU, associated with the propagation of internal gravity waves (IGWs) triggered by the small tsunami. By comparing the IGWs' arrival times in the ionosphere with tsunami wave arrivals at tide gauges, we found that optimal ionospheric TEC observation geometries detected the tsunami's presence before it reached the Kos and Heraklion coastlines. Our findings demonstrate that even small TEC variations can complement existing tsunami early warning systems. This is particularly valuable in the Mediterranean region, where such phenomena remain underexplored. Integrating TEC data with traditional seismic sensors and sea level measurements can enhance early warning systems, improving their capacity to detect and mitigate the effects of small but significant tsunamis.

The results are published in Fuso & Ravanelli (2024) [1].

[1] Fuso, F., & Ravanelli, M. (2024). Probing the ionospheric effects of the 2020 Aegean Sea earthquake: Leveraging GNSS observations for tsunami early warning in the Mediterranean. Journal of Geophysical Research: Space Physics, 129(12), e2024JA032946.

[2] Occhipinti, G., Lognonné, P., Kherani, E. A., & Hébert, H. (2006). Three‐dimensional waveform modeling of ionospheric signature induced by the 2004 Sumatra tsunami. Geophysical research letters, 33(20).

[3] Occhipinti, G., Rolland, L., Lognonné, P., & Watada, S. (2013). From Sumatra 2004 to Tohoku‐Oki 2011: The systematic GPS detection of the ionospheric signature induced by tsunamigenic earthquakes. Journal of Geophysical Research: Space Physics, 118(6), 3626-3636.

How to cite: Fuso, F. and Ravanelli, M.: Investigating Ionospheric Disturbances from the 2020 Samos Earthquake and Tsunami: Advancing GNSS-Based Tsunami Early Warning in the Mediterranean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10748, https://doi.org/10.5194/egusphere-egu25-10748, 2025.

Global navigation satellite systems (GNSS) are used for various applications in the Earth and atmospheric sciences, navigation, surveying and mapping, as well as in early warning systems for geo-hazards. Solutions are often required to not only be of high accuracy, integrity, and continuity, but also to be available in real-time with a delay of only a few seconds. A prerequisite for real-time precise point positioning (PPP) are precise satellite orbit and clock products. While satellite orbits can be predicted with high precision, at least for a few hours, the satellite clocks have to be estimated using real-time GNSS data from a global network of reference stations and distributed via real-time data streams to the user. GFZ is operating a real-time GNSS analysis center, which is contributing to the Real-Time Service (RTS) of the International GNSS Service (IGS). In this contribution, we introduce the new GFZ in-house real-time GNSS network analysis software that is currently being developed and provide an initial assessment of the generated products.

In the first development stage that is presented in this contribution, the generated products contain satellite orbits and satellite clocks referring to the ionosphere-free code observations. The orbits are taken from the predicted part of the operational GFZ IGS ultra-rapid GPS, GLONASS, and Galileo solution, which are updated every three hours. The associated satellite clocks are estimated every five seconds using a recursive least-squares estimator from globally recorded real-time dual-frequency code and phase observations, together with receiver clock parameters, tropospheric zenith delay parameters, inter-system biases, and carrier-phase ambiguities.

Important aspects are the data cleaning to obtain high-quality results and an efficient implementation of the estimation filter to satisfy the delay requirements of the products – less than five seconds for the IGS. For the data cleaning and cycle-slip detection, the concept of single-receiver, single-channel integrity is used, in which the uniformly most powerful invariant test statistics are evaluated separately for each satellite-receiver link using its code and phase observations of two consecutive epochs. For the estimation filter, a sequential Kalman filter implementation using the standard covariance form is used. ‘Sequential’ refers to the strategy that the scalar observations of the same epoch are processed sequentially one at a time, leading to a more efficient operation of the filter compared to the case that the entire vector of measurements is processed at once. With this strategy, the processing time per epoch is around two seconds.

An initial evaluation of this real-time satellite orbit and clock product will be presented by means of a direct comparison to post-processed multi-GNSS reference products and a comparison of PPP analyses using in addition also broadcast navigation data and real-time products of other analysis centers.

How to cite: Brack, A., He, S., Du, S., and Wickert, J.: Real-time GNSS for geosciences: Initial assessment of new data products from GFZ, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10805, https://doi.org/10.5194/egusphere-egu25-10805, 2025.

The high latitudes are widely recognized as the most disturbed region of the ionosphere. The reason for that is the shape of the geomagnetic field and, related to this,  the precipitation of energetic particles originating from the solar wind. The consequence of the strong plasma variation in the polar and auroral ionosphere is the deterioration of GNSS signal amplitude and phase, which may lead to losses of phase lock and cycle slips. The latter impact results in challenging scenarios for GNSS precise positioning based on phase data,  but it may also be used to indicate the high-latitude ionosphere conditions. Since there is a correlation between GNSS signals scintillation and cycle slips, the analysis of the second parameter may support the climatological investigations for this area. Such an assumption allows us to use conventional GNSS data from permanent networks (of 1-30 s sampling rate), significantly extending the spatiotemporal distribution of measurements. Nevertheless, the adoption of cycle-slips number as a parameter describing ionospheric activity has to be preceded by cross-evaluation of its behaviour for different receivers and signals. This step is crucial, considering the increasing number of GNSS constellations and signals.

Motivated by such developments, we investigated the occurrence of cycle slips in GNSS phase data recorded by stations located at northern high latitudes. The basis for the analysis was multi-GNSS observations (GPS, GLONASS, Galileo, BDS) collected by permanent IGS/EPN stations. As a test period, we selected two major geomagnetic storms in 2024, which took place in May and October. The analysis confirms significant differences between the number of cycle slips for a particular system and signal. The discrepancies are also observed for collocated stations equipped with different receivers. The results indicate a need for unifying multi-GNSS cycle-slip numbers for climatological ionospheric studies.

How to cite: Sieradzki, R. and Paziewski, J.: The cycle-slips occurrence at high-latitude GNSS stations during geomagnetic storms – inter-receiver and inter-signal comparison, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12253, https://doi.org/10.5194/egusphere-egu25-12253, 2025.

The growing interest of the GNSS community in computing GNSS series using the iPPP (Precise Point Positioning with integer ambiguity resolution) mode with the GINS software and the products of the CNES/CLS analysis center (GRG products) culminated in 2022 with the SPOTGINS project. This initiative enables several research laboratories to cooperate in processing a global network of stations, benefiting from the expertise of the IGS analysis center and the advanced quality of the GRG products.

This standardization and collaboration require a unified computational strategy, involving the same version of the GINS software, identical configurations (products, corrections, models, constellations), and consistent metadata. Currently, daily station positions are computed using GPS and Galileo constellations, using the “G20” orbits and clocks from the IGS CNES-CLS based on ITRF2020, FES2014b ocean tidal loading and VMF1 mapping functions.

SPOTGINS started in 2022 with the collaboration between the OMP in Toulouse, the EOST in Strasbourg and the LIENSs in La Rochelle, whose massive calculations with GINS were already being done for several years. In 2023 and 2024, other groups expressed interest in joining SPOTGINS: the GeF/Cnam in Le Mans, the IPGP/IGN in Paris and the OSUG/ISTerre in Grenoble. Each member pursues different scientific objectives, but all contribute  collectively to the dissemination of PPP series for the community through the Geodesy Plotter of the FormaTerre data and service hub.

How to cite: Boy, J.-P., Fériol, F., Gravelle, M., Janex, G., Loyer, S., Nahmani, S., Nicolas, J., Pollet, A., Sakic, P., Santamaría-Gómez, A., and Tsapong-Tsague, A.-B.: SPOTGINS: A New Global GNSS Daily iPPP Solution Derived Using GINS software , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12545, https://doi.org/10.5194/egusphere-egu25-12545, 2025.

The southwest Pacific Region regularly produces tsunamis triggered by strong earthquakes of magnitude up to M8.1 associated to its complex tectonics and subduction processes. According to the NOAA/NCEI database, these tsunamis represent about one quarter of the tsunamis recorded worldwide. Some of them have been catastrophic for coastal populations in terms of the number of dead and injured and destructions of infrastructures or agriculture land. For example, the 2007 Solomon Islands & the 2009 Samoa tsunamis killed 50 and 192 people, respectively and did hundreds of millions of US dollars in damage. The present study focuses on the Solomon Islands which has suffered from several recent destructive tsunamis, including the tsunami in 2007, and a doublet tsunami in 2016. Only a few tide gauges and 2 Australian DART captured the tsunami signal, demonstrating the need for more densely spaced observations and direct measurements from the ocean, in order to improve the warning procedures, reducing the alert timing. One way to increase this observing capacity is to fill the geodetic observation gap in the ocean using a network of cargo-ships equipped with GNSS systems tracking anomalous variations of the sea-level. These measurements can potentially detect tsunamis of different origins. To complete the few available studies focusing on the Solomon Islands tsunamis, the project aims (i) to model the 2007 and 2016 tsunamis using the records/observations on land or close to the shore (e.g., seismic network, land-based GNSS and tide-gauges data), (ii) to compare their source and impact on population and infrastructure, (iii) to analyze what a constantly moving cargo-ship GNSS network might experience in terms of tsunami travel time and tsunami predicted amplitudes, and (iv) to determine how useful such a cargo-ship GNSS network would be to increase our ability to detect and respond to these hazards through local early warning. By exploring the relationship between tsunami sources, travel times and amplitudes using ships’ locations, the study seeks to determine the ability of a defined regional ship network to function as a low-cost method to improve the detection of tsunamis, and to improve effective warnings and hazard mitigation for coastal areas and the exposed communities in the region.

How to cite: Thomas, B. E. O., Roger, J., and Foster, J.: Evaluation of the ability of a cargo-ship GNSS network to detect tsunamis in the Solomon Islands region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13055, https://doi.org/10.5194/egusphere-egu25-13055, 2025.

As urban populations continue to grow, the demand for precise positioning has become increasingly critical for various applications, including navigation, location-based services (LBS), transportation, delivery, and logistics. Global Navigation Satellite Systems (GNSS) are widely utilized for positioning; however, they encounter significant challenges in urban canyons, where signal obstructions and reflections can degrade positioning accuracy by tens to hundreds of meters.

To address these challenges, existing consistency check methods have been developed to detect and exclude erroneous observations from multiple GNSS constellations, thereby improving performance in open or low-density urban environments. Nevertheless, high-density urban areas present difficulties, as the majority of GNSS signals are often compromised by non-line-of-sight (NLOS) reception and multipath interference. While the integration of inertial sensors with GNSS technology has shown effectiveness in addressing GNSS outages, the accumulation of drift errors in pedestrian dead reckoning (PDR) still hinder performance in dense urban settings where GNSS solutions are consistently unreliable.

In this study, we propose a novel approach that tightly integrates PDR and GNSS data in the measurement domain to effectively identify fault-free measurements amidst a backdrop of contaminated signals. We introduce a multi-epoch smoothing algorithm designed to enhance positioning accuracy. Our method employs a two-stage consistency check algorithm to mitigate multipath effects, incorporating both satellite quality assessments and grid quality evaluations based on raw GNSS observations and inertial sensor data. Notably, we leverage time-series residuals from multi-epoch GNSS observations to identify fault-free measurements, moving beyond the limitations of single-epoch data. Additionally, grid quality is evaluated based on the discrepancies in residuals among high-quality satellites. To bolster the robustness and reliability of positioning, our algorithm integrates a positioning scheme that utilizes weight smoothing based on multi-epoch grid mapping and outlier mitigation through density-based spatial clustering of applications with noise (DBSCAN) clustering.

Field experiments conducted in typical urban environments in Hong Kong, utilizing a standard smartphone as the receiver, demonstrated substantial improvements over conventional consistency check methods and chip outputs. Our findings reveal that traditional consistency check methods underperformed compared to chip outputs in dense urban areas. In contrast, the proposed method significantly enhanced positioning accuracy across all trials, achieving accuracies ranging from 2m to 10m, compared to chip outputs that varied from 5m to 58m. The proposed approach yielded an improvement rate of 50% to 88% across different urban densities.

This innovative method is compatible with most consumer-grade devices, requiring no additional hardware, thereby offering enhanced convenience and intelligence for urban residents. Its ease of implementation across various brands and real-time operation with low computational load make it a versatile solution for improving positioning accuracy in complex urban environments.

How to cite: luo, H., Yang, Y., Mi, X., Ding, M., and Chen, W.: Enhancing GNSS Positioning Accuracy in Urban Canyons: A Multi-Epoch Residual-Based Consistency Check and IMU-GNSS Tight Coupling Approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14893, https://doi.org/10.5194/egusphere-egu25-14893, 2025.

In recent decades, Precise Point Positioning (PPP) has become a well-established GNSS positioning method that is used in various applications. PPP is characterized by the use of precise satellite products (satellite orbits, clocks, and biases) combined with the accurate modeling of various error sources and elaborate algorithms. This way, PPP allows us to achieve position accuracies at the centimeter or even millimeter level. Nowadays, several institutions provide high-quality multi-GNSS satellite products through the International GNSS Service (IGS). These modern satellite products enable, for example, integer ambiguity fixing and incorporating observations from multiple GNSS in the PPP solution, typically enhancing the PPP performance.

In this contribution, we provide an overview of the currently available multi-GNSS satellite products and discuss their potential benefits of using 2+ frequencies and alternatives to the ionosphere-free linear combination. These methods are considered advantageous for improving PPP performance, particularly regarding convergence time. We present PPP results using GPS, GLONASS, Galileo, and BeiDou observations and satellite products from different institutions, focusing on integer ambiguity resolution (PPP-AR). Additionally, we test the combined multi-GNSS product developed by the GNSS Research Center at Wuhan University as part of the IGS PPP-AR Pilot Project. We evaluate the resulting coordinate accuracy, convergence behavior, and ambiguity fixing rates. The PPP investigations are conducted with the open-source raPPPid, part of the Vienna VLBI and Satellite Software (VieVS PPP). 

How to cite: Wareyka-Glaner, M. F. and Möller, G.: Enhancing PPP Performance with Multi-GNSS Satellite Products and Integer Ambiguity Resolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15232, https://doi.org/10.5194/egusphere-egu25-15232, 2025.

Seismic monitoring depends on accurately identifying P-wave and S-wave arrivals, which are critical for earthquake localization and Earthquake Early Warning (EEW). In EEW networks, a Global Navigation Satellite System (GNSS)-driven geodetic component enhances lead-time estimation and ground-shaking assessment, particularly for large earthquakes (Mw > 6.0). Advancing S-wave detection algorithms is essential to providing fast and reliable warnings to communities.

This study presents a sliding-window-based algorithm designed to detect the first time of arrival (ToA) of S-waves in high-rate (<1 Hz) GNSS instantaneous velocity time series without frequency-domain pre-filtering. The algorithm employs a three-phase process: (1) preprocessing, (2) statistical analysis and hypothesis testing for extracting ground-shaking disturbances, and (3) S-wave picking. It is implemented in an open-source Python-based toolbox, which also provides auxiliary seismic data, including ground-shaking duration, component-wise Peak Ground Velocity (PGV), and waveform energy.

The algorithm’s performance was evaluated using data from the 2016 Mw 6.2 Norcia and 2023 Mw 7.7 Kahramanmaraş-Gaziantep earthquakes. Results showed root mean square errors (RMSE) of 1.8 seconds and 3.8 seconds, respectively, when compared to ground-truth S-wave arrivals derived from P-wave readings on seismic waveforms recorded within 5 km of the GNSS sensors using the auxiliary Pphase-Picker software. The P-wave readings were extrapolated to GNSS sensor locations assuming equal P-wave velocities and a P-to-S-wave velocity ratio of 1.5.

Severe ground-shaking durations of up to 80 and 250 seconds, along with short S-P times of 3-5 seconds for the town of Norcia and the city of Gaziantep, highlight the severity of these events. This study demonstrates the new algorithm’s potential to enhance GNSS-based S-wave detection.

How to cite: Lapadat, A. M., Pierzchala, H., Kudłacik, I., Cai, Y., Aponte, O., Nastase, E. I., and Lackowski, M.: Automated S-Wave Arrival Timing in GNSS Instantaneous Velocity Data Without Frequency-Domain Pre-Filtering, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15685, https://doi.org/10.5194/egusphere-egu25-15685, 2025.

To meet the demanding requirements in terms of accuracy and availability, GPS has introduced the signals on L5 that are compatible to Galileo E5a signals. The L5 signal was designed to mitigate the multipath and poor performance in harsh environments such as indoor, forests, and areas affected by jamming. As the L2 signal will become obsolete in the future, action must be taken to take advantage of the modern signal type which is currently broadcast by 19 out of GPS satellites. This is particularly important for some future LEO satellites (e.g. EPS-SG) which will rely exclusively on L1/L5. CODE (Center for Orbit Determination in Europe) is building up a prototype processing chain to generate L1/L5-based clock and bias products in addition to the classic L1/L2-based processing chain. First results regarding analysis product consistency are presented.

How to cite: Kalarus, M., Schaer, S., Dach, R., Arnold, D., and Jaeggi, A.: Towards new CODE analysis products based on GPS L1/L5 signals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17355, https://doi.org/10.5194/egusphere-egu25-17355, 2025.

The tropospheric effect is considered as one of the most significant sources of error limiting GNSS positioning accuracy. In addition, atmospheric mass loading, which is seasonally variable, can also affect the repeatability of daily GNSS positions to a minor level. Therefore, the correct modelling of tropospheric and atmospheric loading effects is crucial to achieve the suitable accuracy, especially in high-accuracy GNSS applications. The aim of this work is to study the impact of tropospheric modelling and atmospheric mass loading on the repeatability of daily GNSS solutions. The research methodology is based on the analysis of GNSS data obtained from the IGS network, incorporating multiple processing scenarios including different mapping functions, elevation masks, and atmospheric mass loading. The analysis studies data from contrasting geographical locations (mid-latitude and polar regions), and accounts for seasonal variations by analysing measurements taken during both summer and winter periods, enabling a comprehensive assessment of how these various factors influence GNSS data processing outcomes, especially the daily position repeatabilities. The obtained results show that the efficiency of the mapping functions varies from one region to another. Furthermore, the consideration of atmospheric mass loading affects the performance of the mapping functions.

How to cite: Dekkiche, H., Namaoui, H., and Bouaoula, W.: Impact of tropospheric and atmospheric loading models on the repeatability of GNSS solutions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17541, https://doi.org/10.5194/egusphere-egu25-17541, 2025.

Recently, we have observed remarkable progress in algorithms aimed at precise point positioning (PPP) based on uncombined GNSS observations, also with an integer ambiguity resolution. Despite the high potential of such a model, its performance still depends on several factors, among which is the a priori information on slant total electron content (STEC), which is crucial. The ionospheric corrections may be obtained by converting VTEC from global ionosphere maps (GIM) using the selected ionospheric mapping function (MF). Thus, the accuracy of such STECs depends on the uncertainties introduced by both GIMs and MFs. Considering the latter, the most common approach is using a single-layer model (SLM) with a zenith angle as a parameter. However, it may be less effective for regions with strong TEC gradients that depend on azimuth. Improving such areas seems feasible with the support of ionosphere models and multi-layered mapping functions.

In this study, we evaluate the new multi-layered mapping functions. The new functions were developed, taking the Neustrelitz TEC Model as a basis. In this case, the ionosphere comprises numerous thin shells, and the ratio of aggregated slant and vertical TEC values provides the modeled mapping factors. Such derived MFs were validated based on PPP positioning performance. Also, an agreement analysis using the geometry-free linear combination was performed to assess the MFs in the GNSS observation domain.  The preliminary tests involved GNSS data from several globally distributed stations, corresponding to different daily patterns of the ionosphere. The analysis provides the statistics for the low solar activity period (year 2019).  According to the results, we can report a slight benefit from applying the multi-layered mapping function for PPP performance compared to the standard SLM approach. The advancement is the most noticeable for the positioning initialization period and, therefore, is reflected in the convergence time. The analysis performed with the geometry-free linear combination is consistent with PPP results, and it highlights the highest potential of the multi-layered mapping function for the equatorial region.

How to cite: Wielgosz, P., Sieradzki, R., Paziewski, J., Hoque, M., Frauenberger, O., Dhital, N., Nykiel, G., Milanowska, B., and Orus Perez, R.: Applicability of multi-layered mapping function to STEC/VTEC conversion – validation in PPP positioning and GNSS observation domains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18016, https://doi.org/10.5194/egusphere-egu25-18016, 2025.

This study addresses the scientific question of the applicability of low-cost antennas to the most precise GNSS applications. First of all, we inspect the implications of the availability and quality of low-cost antenna PCC models for precise positioning. From this point of view, we analyze the selected performance indicators of multi-constellation positioning with the representative set of low-cost mass-market GNSS receiver antennas. The processing strategy was based on the relative positioning model, considered the most reliable and precise one. To isolate the antenna-related errors from atmospheric propagation ones, we conducted an experiment based on an ultra-short baseline. As the main indications of low-cost antenna performance, we considered distance and height residuals, defined as the difference between benchmarks and the retrieved from GNSS measurements. We found that the low-cost antenna's PCV effect may significantly affect the final results. On the other hand, the results obtained using certain configurations of low-cost antennas were characterized by only slightly higher standard deviations and discrepancies with respect to benchmark values than those obtained with surveying or geodetic equipment. We identify several sets of low-cost antennas where distance residuals do not exceed 4 mm and height residuals do not exceed 6 mm, which shows the low-cost antenna performance comparable to those achieved using high-grade antennas. On this basis, we conclude that selected low-cost antennas can meet the requirements of high-precision surveying applications.

How to cite: Dawidowicz, K., Paziewski, J., Krzan, G., and Stępniak, K.: On the applicability of low-cost GNSS antennas to precise surveying applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18548, https://doi.org/10.5194/egusphere-egu25-18548, 2025.

Low Earth Orbit Positioning Navigation and Timing (LEO-PNT) is an emerging satellite navigation concept to augment current Global Navigation Satellite Systems by placing satellites close to Earth, at around 600-1200 km altitude. This proximity leads to a rapid change in satellite geometry, which is mainly expected to reduce the convergence time of real-time precise positioning. To realize the benefits of LEO’s faster dynamics, the positions and clock offsets of the LEO-PNT satellites must be known with a high accuracy and low latency. In existing GNSS constellations deployed in Medium Earth Orbit (MEO), global networks of ground stations are generally used to estimate the satellite positions and clock offsets, which are then uplinked to the satellites for broadcast to users. This same approach for LEO-PNT systems would require an extensive ground network due to their closer proximity to Earth. Instead, on-board GNSS-based Precise Orbit Determination (POD) for LEO-PNT satellites offers a feasible alternative. 

This study investigates the impact on ground positioning users when performing on-board POD for LEO-PNT satellites. The numerical assessment consists of two parts: in the first part we focus on the on-board POD results by using Sentinel-6A real-world data from DOY 118-124 in 2024 including both GPS and Galileo observations. A reduced-dynamics extended Kalman filter POD approach with degraded dynamical models is used to replicate on-board processing conditions. Various types of GNSS corrections are tested to assess the POD accuracy achievable on board. 3D RMS orbit errors of 2.8 cm, 4.8 cm, 9.9 cm, and 15.2 cm are obtained in the numerical POD computations respectively based on the CODE MGEX final products (COD), the CNES Real-Time products (CRT), the Galileo High Accuracy Service corrections (HAS), and the broadcast ephemerides (BRD). Moreover, we compare the estimated receiver clock offsets with respect to a precise reference clock solution computed in a batch-least squares approach without orbital model degradation. 

In the second part, we focus on the impact of these LEO orbit and clock errors in an end-to-end simulation of kinematic float-PPP for a ground user. A LEO space segment of 28 satellites was simulated to augment the cases of GPS only, Galileo only, and GPS+Galileo, while considering different product configurations. The results showed that a LEO space segment with CRT-level orbit and clock errors could consistently improve the convergence time as compared to each corresponding stand-alone MEO case. For a HAS ground user using GPS and Galileo, the LEO with HAS-level orbit errors achieved 20 cm horizontal convergence under 3 minutes when clock errors were neglected. At the same time, the overall positioning accuracy results did not show significant improvement nor degradation from including the LEO space segment. Based on our preliminary findings, the expected benefits of LEO-PNT augmentation are only possible when sufficiently accurate orbits and clocks are estimated and provided to users. Still, the impact of the correction latency and availability shall be further investigated in future works.

How to cite: Oduber, J., Massarweh, L., and van den IJssel, J.: Impact of on-board satellite orbits and clocks estimation for LEO-PNT ground positioning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19075, https://doi.org/10.5194/egusphere-egu25-19075, 2025.

Precise point positioning real-time kinematic (PPP-RTK), by capitalizing on its state-space representation (SSR) and its associated flexibility, is naturally emerging as one of the prevalent Global Navigation Satellite System (GNSS) techniques for high-precision positioning. The determination of unbiased ambiguity-resolved positional parameters becomes possible once single-receiver users get access to SSR corrections. However, the fact that such SSR corrections are often estimated in a recursive manner, based on a set of assumptions and a singularity-basis (S-basis) choice made in an arbitrary fashion by the correction provider (i.e., a GNSS network), may lead to serious pitfalls which the PPP-RTK user should be aware of when interpreting the delivered corrections. In this contribution, we will present the intricacies inherent in multi-epoch filtered PPP-RTK corrections and address the consequence of the corrections’ dependency on the provider’s S-basis. Through illustrative examples, it is shown how one can be misled by merely analyzing the estimable satellite clock solutions’ temporal characteristics, and how the distributional properties of the satellite phase bias solutions can be affected in case only their fractional part is delivered, contrary to the users’ usual expectation of being equipped with Gaussian-distributed phase biases. Next to this analysis, the important roles played by the correction latency and time correlation are addressed in both ambiguity-resolved positioning and the associated ambiguity-float and -fixed confidence information reported by the user estimation process.

How to cite: Psychas, D., Khodabandeh, A., and Teunissen, P. J. G.: On the intricacies of multi-epoch filtered PPP-RTK corrections and their impact on GNSS ambiguity resolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19300, https://doi.org/10.5194/egusphere-egu25-19300, 2025.

Since 2016, Android smartphones have allowed access to the raw GNSS data, leading to significant improvements in positioning accuracy. Modern devices now support dual-frequency GNSS and multiple satellite systems, making positioning more reliable. Despite significant efforts in GNSS smartphone positioning, including using the Galileo constellation, several important issues still need to be addressed. Galileo signals have more complex modulation schemes compared to GPS signals. Practical tests show that after a short period, Galileo measurements' status may change from 'TOW Decoded' to 'E1C 2nd Code' status, where TOW represents the GNSS time of week. The receiver can stay on the 'E1C 2nd Code' status for several minutes. Some Galileo-ready chips track the data component to decode the navigation message. Once the ephemerides and clock data are decoded, they switch to tracking the E1C (pilot component), resulting in the 'E1C 2nd Code' status and ambiguous pseudoranges. In the current Galileo tracking approach, some satellites remain in 'TOW Known' or 'TOW Decoded' status for over an hour, while others switch to 'E1C 2nd Code Lock', resulting in ambiguous pseudoranges. The algorithm used to determine the tracking status for each satellite remains unclear. The white paper published by the European GNSS Agency’s (GSA) recommends checking the Galileo tracking status and highly advises using Galileo measurements only when in the E1C 2nd Code status.

In this research, we will show that a 4 ms jump is still observed in some datasets, even though the tracking status is E1C 2nd Code. This confirms that verifying the signal tracking status alone is insufficient, as 4 ms jumps in the data can still occur despite this check. During these "jump epochs," erroneous measurements can adversely affect positioning accuracy. To investigate this issue, data collected by the Xiaomi Mi8 and Google Pixel 8 Pro devices are used. The results indicate that these jumps vary between devices and over time. The results also show that these jumps still occur, even though the tracking status is E1C 2nd Code.

This 4 ms jump has also been addressed by Galluzzo et al. (2018) during the 2018 IPIN conference. They proposed a straightforward method to correct the pseudorange by detecting jumps through the difference between two consecutive epochs. If the difference is around 4 ms, the subsequent pseudoranges are adjusted accordingly. Although the theory behind this method is straightforward and effective in many cases, it cannot detect all jumps, for example, when those satellites first appear or when the pseudorange is missing. In this research, we employ the Observation Minus Calcaulation (OMC) to solve this issue and find the undetected 4 ms jumps. Finally, we investigate the accuracy of the kinematic data from Xiaomi Mi8 and Google Pixel 8 Pro devices with and without corrections for the 4 ms jumps. The results showed performance improvement in terms of the root mean square (RMS) and the 50^th percentile of the horizontal positioning error after applying the correction for the 4 ms jump in Galileo measurements.

How to cite: Zangenehnejad, F., Elsheikh, M., Liu, F., and Gao, Y.: Investigating Galileo Signal Tracking Challenges in Smartphones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20749, https://doi.org/10.5194/egusphere-egu25-20749, 2025.

This study examines the stability and temperature variations of SAPOS reference stations across Lower Saxony and neighboring federal states over a four-year period (2017–2020). SAPOS, the Satellite Positioning Service of the German National Survey, provides high-precision geodetic
reference points essential for applications such as surveying, navigation, and geographic information systems (GIS). Data from 43 SAPOS stations in Lower Saxony, ten SAPOS stations in adjacent regions, and 54 German Weather Service (DWD) stations were analysed using custom programs in Python
and MATLAB. The findings demonstrate the high SAPOS availability and station quality, though systematic effects were identified in the cleaned time series of topocentric coordinates for certain stations. These effects relate to multipath sensitivity, assessed using the Multipath Indicator (MPI),
which reflects signal reflection interference, confirming the high quality of SAPOS stations. The study corrected these effects via drift and offset adjustments and outlier removal. The analysis investigated five categories of deviations, revealing recurring patterns influenced by station type and installation characteristics. Notably, unilateral solar exposure and temperature fluctuations at the Braunschweig station caused deviations of up to 5 mm in the north and east components of topocentric coordinates.

How to cite: Zhu, Y., Schön, S., and Jahn, C. H.: Analysis of Stability and Temperature Variations in SAPOS Reference Stations in Lower Saxonyand Adjacent Regions between 2017 and 2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21876, https://doi.org/10.5194/egusphere-egu25-21876, 2025.

As Global Navigation Satellite System (GNSS) positioning technology rapidly advances, Precise Point Positioning (PPP) has found widespread application in the mass market, particularly for vehicle navigation. PPP enhanced by atmospheric corrections was proven to be an effective rapid high-precision positioning method for wide-area users. The Quasi‐4‐Dimension Ionospheric Modeling (Q4DIM) is a flexible atmospheric model that enables enhanced PPP positioning from wide-area to regional applications. It divides the slant ionospheric delays (SIDs) from a station network into various clusters based on the latitude and longitude of the Ionosphere Piercing Point (IPP), satellite elevation, and satellite azimuth. These clusters are used for the correction of atmospheric errors in PPP and ionosphere monitoring. As devices capable of GNSS positioning become increasingly available in the mass market, effectively utilizing these observations could significantly reduce costs and broaden the range of rapid PPP services. In this contribution, we developed a crowdsourcing Q4DIM approach, where users upload SIDs verified for integrity to the cloud server, which classifies and stores the data based on accuracy, location, and the level of services utilized. Then, the cloud server constructs and disseminates diversity Q4DIM maps according to the different level attributes of SIDs. Finally, the users utilize the updated Q4DIM maps to achieve faster and more precise positioning. 144 sets of control experiments are conducted with observations from European Continuously Operating Reference Stations (CORS). Stations with an average inter-station distance of about 200 km are chosen as reference stations that are used for extracting the original Q4DIM map. The remaining stations are established as dynamically estimated crowdsourced stations for extracting the crowdsourced Q4DIM map. Results show that the performance of PPP enhanced by the crowdsourced Q4DIM map is significantly improved than those of the original Q4DIM map. The positioning error series of the original solution converges within 9 epochs to within 10 cm in the horizontal direction and 20 cm in the vertical direction, while the positioning error series of the crowdsourced solution reaches 2.3 cm in the horizontal direction and 7.6 cm in the vertical direction in 2 epochs. Compared to the original solution, the positioning accuracy of the new method improved by 48.2% in the horizontal direction and 41.2% in the vertical direction.

How to cite: Wang, B., Gu, S., Zhu, J., and Hu, J.: A Cost-Effective Crowdsourced Q4DIM Method for Rapid PPP Implementation in Wide Areas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3961, https://doi.org/10.5194/egusphere-egu25-3961, 2025.

Lately, multi-frequency GNSS signal availability have become more commonplace, while dual-frequency receiving capability, previously restricted to expensive geodetic-grade instruments, appeared in cost-efficient and low-cost receivers. Therefore, large networks of GNSS stations with high positioning accuracy can now be deployed at limited cost, benefitting a variety of geoscience applications.

To take advantage of the developments in dual-frequency capabilites, GFZ and spin-off company maRam developed the tinyBlack GNSS receiver. The tinyBlack is compact, robust, versatile and low-power. It is equipped with one of various GNSS receiver boards and can be integrated with additional sensors. It provides a flexible, economical solution for geoscientific monitoring stations for, e.g., tectonic, volcanic and earth engineering monitoring. We evaluate the geodetic performance of different dual-frequency receiver boards in the tinyBlack.

We conduct a zero-baseline test, comparing three different receiver boards (Septentrio AsteRx-m3, Ublox  and SwiftNav Piksi) in a tinyBlack receiver and a separate, reference receiver (Septentrio PolaRx5). All boards have at least dual-frequency (L1/L2, E1/E5b) support and were simultaneously connected to a static geodetic choke-ring antenna. We first check data quality with GNut/Anubis, including observation availability, multipath linear combination, and signal-to-noise ratio. We then analyse PPP solutions with GFZ-provided precise orbits and satellite clock offsets, computing both daily and sub-daily kinematic coordinates. We compare observation residuals, coordinate estimates, and troposphere estimates. We find that the Ublox and Piksi receivers struggle more with multipath effects than the geodetic-grade receivers, despite using the same antenna in a good test location with a clear view of the sky. We also find that the Piksi has fewer observations, including a hard-coded low-elevation-angle cutoff. Probably as a consequence, it also the highest signal-to-noise ratio and lower residuals than the Piksi. PPP daily coordinate performance is vertically worse than, and horizontally comparable horizontally with, the cost-efficient receivers. Sub-daily coordinate performance is worst with the Piksi.

We also conduct a test step-wise moving antenna test to evaluate the capability of the Piksi receiver specifically to recover known displacement. We move the antenna by 5 cm every hour, alternatively forwards and backwards in a repeated 2-hour cycle, both horizontally (north-south) and vertically in separate tests. We compute kinematic PPP solutions with GFZ-provided precise orbits and clock offsets. We find that the average amplitude of the step can be recovered successfully and that both the standard deviation of the amplitudes and the scatter of coordinates at each point in the cycle is greater for the vertical component.

We finally perform data quality controls and show network-solution estimated coordinates of four GNSS stations in a field installations. The stations are co-located with seismometers installed in Italy as part of the DETECT (DEnse mulTi-paramEtriC observations and 4D high resoluTion imaging) project, which aims to acquire a dense multiparametric dataset imaging near-fault, active, slow tectonic deformation in a portion of the southern Apennines mountains with destructive historical seismicity.

In conclusion, we appreciate the developments spurred by the availability of dual-frequency signals and look forward to further field applications of dual-frequency receivers for geoscience research.

How to cite: D'Acquisto, M., Ramatschi, M., and Männel, B.: Cost-efficient dual-frequency GNSS receivers: quality assessment for geophysical applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7129, https://doi.org/10.5194/egusphere-egu25-7129, 2025.

Global Navigation Satellite System (GNSS) technology, thanks to its high accuracy, is appropriate for monitoring structures, natural and anthropogenic hazards, as well as navigation and positioning. The Galileo High Accuracy Service (HAS) augmentation service recently released by the European Space Agency (ESA) is a new solution that could accelerate the development of mass-market technologies using the Global Navigation Satellite System (GNSS). Galileo HAS is designed to provide horizontal and vertical accuracies of 20 cm and 40 cm, respectively; it can be used in all legacy GNSS applications from structural monitoring to drone trajectory tracking using low-cost GNSS receivers.

This study evaluates the use of Galileo HAS with geodetic grade as well as low-cost receivers, analysing the results obtained in static, pseudo-kinematic, and kinematic solutions. The results indicate that Galileo HAS currently provides positioning accuracy at a to that comparable level of less than 10 cm, regardless of the use of geodetic or low-cost receivers. The results of integrating Galileo HAS with low-cost receivers show that it represents an important step in the development of available real-time positioning solutions.

In addition, the study showed that Galileo HAS meets key requirements in monitoring water vapour in the troposphere, as well as seismic displacement, by achieving real-time accuracy levels required for seismic displacement tracking and weather modelling. Comparative analyses with other GNSS correction streams show that HAS has lower accuracy in selected statistics, such as vertical accuracy. However, its near-global availability and high accuracy still make it a viable alternative.

How to cite: Marut, G., Hadas, T., Kazmierski, K., Kudłacik, I., and Bosy, J.: Advancing Real-Time GNSS Applications: Performance of Galileo HAS in Precision Navigation and Low-Cost Receiver Integration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8972, https://doi.org/10.5194/egusphere-egu25-8972, 2025.

Low-cost GNSS technology has recently expanded as an alternative to geodetic receivers in many applications, including pedestrian navigation, autonomous vehicles, atmospheric monitoring, and precision agriculture. Considering the capabilities of the receiver in terms of power consumption, size, and cost, together with the ability to record multi-GNSS observations, the low-cost receivers and patch antennas have appealed to many users. However, there exist some challenges to be addressed. Such hardware is inherently sensitive to the multipath effect, and the noise level in the observations is relatively higher, resulting in a lower carrier-to-noise density ratio (C/N0). More outliers are encountered for kinematic applications in challenging environments such as urban areas. Therefore, both realistic stochastic modeling (e.g., C/N0-dependent) and the identification of outlier observations are crucial issues for achieving reliable positioning when low-cost GNSS hardware is used. This study aims to investigate pedestrian navigation performance using low-cost GNSS and to enhance positioning accuracy through the implementation of the improved Single Point Positioning (SPP) algorithm, thanks to the code sequence. The technique employs a powerful quality control scheme to mitigate outlier observations. The method consists of two main steps: (i) If the products or measurements used for epoch-by-epoch solutions are troublesome for certain satellites, the median absolute deviation (MAD) method is applied to eliminate these observations. (ii) The remaining observations are then reweighted using a standardized residual-based Institute of Geodesy and Geophysics (IGG) III method during the least-squares. A kinematic test experiment was conducted to validate the usefulness of the approach for which observations were collected from four satellite systems with a 2-s sampling interval of approximately 20 min using a low-cost GNSS antenna (u-blox ANN-MB-00-00) and receiver (u-blox ZED-F9P). The multi-GNSS SPP solution with code observations of GPS L1, GLONASS G1, Galileo E1, and BDS-3 B1 frequencies was performed in this dataset. A GNSS station very close to the study area was used to obtain the reference trajectory with the post-process kinematic method. Analyzing only the fixed coordinates together with the corresponding SPP solution coordinates, resulted in an RMS value of about 0.50 m achieved in the horizontal component. Results showed how the utilization of proposed techniques can enhance basic SPP solutions that yield meter-level horizontal positioning accuracy. Moreover, the suggested technique improved multi-GNSS SPP solution RMS values by 33% in the horizontal and 19% in the vertical component compared with solutions without outlier detection. A comparison was also made using the findings from two distinct software packages to verify the consistency of the outcomes. The results of the evaluation indicate that the SPP algorithm exhibits comparable performance to that of the other software and validates the effectiveness of the employed technique. Finally, the GPS/GLONASS/Galileo/BDS-3 SPP, exhibiting a 3D RMS value slightly better than 2 m for pedestrian navigation, illustrates the capabilities of low-cost GNSS technology.

How to cite: Birinci, S., Sogukkuyu, F., and Saka, M. H.: Improving pedestrian navigation performance with robust methods for low-cost multi-GNSS , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11204, https://doi.org/10.5194/egusphere-egu25-11204, 2025.

How to cite: Bosser, P., Ancelin, J., Métois, M., Rolland, L., and Vidal, M.: Monitoring of geophysical deformations on a regional scale using the low-cost GNSS collaborative network CentipedeRTK , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11878, https://doi.org/10.5194/egusphere-egu25-11878, 2025.

In this study, we investigate the effect of antenna setup errors upon on the accuracy of position velocities produced from GNSS campaign measurements when gaps in data. Our motivation in this study is to demonstrate the changes in station velocities in time series caused by certain antenna measurement errors, in addition to the reduced frequency of data obtained from campaign-style measurements, which are preferred due to maintenance costs, permanent stations being damaged or even lost while monitoring natural events. We used seven stations from the continuous GPS time series of JPL, NASA from a global network of the IGS. For each station, we generated 1460 data for four years synthetic GNSS campaign time serieswithout gaps and 48 data with one measurement campaign per month. Subsequently, by creating data gaps through monthly campaigns, velocity estimates were made from datasets consisting of 32, 24, 16, and 8 data respectively. The same datasets were augmented with Gaussian noise simulating ±1-3 mm of antenna setup error. Velocity estimates were also made from these augmented datasets. Rms values calculated from antenna error-free datasets ranged between 0.1~0.5 mm for North, 0.2~0.5 mm for East, and 0.5~1.3 mm for Up directions. Rms values also calculated from antenna error datasets ranged between 0.2~0.9 mm for North, 0.2~0.7 mm for East, and 0.5~1.1 mm for Up directions. All velocity estimates were subjected to student t tests. About 1% variation was found for all components, both with and without antenna setup errors. The effect of antenna setup errors on data gaps in campaign-style measurements was demonstrated.

Keywords: GPS time series; GPS campaigns; Velocity estimation; Gaps in data; Antenna Setup Errors.

How to cite: Tuna, M. and Turen, Y.: The Effects of Antenna Setup Errors upon velocities of GNSS campaign measurement when gaps in data., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12633, https://doi.org/10.5194/egusphere-egu25-12633, 2025.

The ionospheric delay is a major error source in the Global Navigation Satellite System (GNSS) positioning, and its accurate estimation is essential for Precise Point Positioning Real-Time Kinematic (PPP-RTK). Traditionally, ionospheric delay estimation relies on a network of permanently deployed high-end geodetic GNSS receivers, which are costly and thus inaccessible for most consumer applications. Moreover, this approach is limited by the sparse spatial distribution and low temporal resolution of the network, leading to significant estimation errors in uncovered environments.

On the other hand, due to the global density and accessibility of low-cost GNSS receivers, such as smartphones, there is a strong demand to develop new methods for precise ionospheric delay estimation using them. Moreover, multi-frequency and multi-constellation GNSS chipsets are now embedded in smartphones including carrier phase observations essential for precise positioning. These advances support the investigation and development of new methods to enable precise real-time GNSS positioning even using smartphones. However, few studies have focused on the application and evaluation of such methods for PPP-RTK positioning.

Therefore, this study aims to develop methods to estimate ionospheric effects using low-cost GNSS receivers and demonstrate that it can provide reliable ionospheric corrections. Additionally, we evaluated ionospheric corrections using two real-time satellite orbit, clock, and code bias products, namely the satellite-based BeiDou PPP-B2b and ground-based Centre National d’Etudes Spatiales (CNES). First, the ionospheric delay estimates generated by a single reference smartphone with uncombined PPP and quality control measures based on solution separation testing is evaluated using of the real-time satellite orbit, clock, and code bias products from BeiDou PPP-B2b and CNES, respectively. Next, the generated ionospheric delay from two correction models is compared to that produced by a high-end geodetic receiver. Finally, the generated ionospheric corrections are applied to single-station-based PPP-RTK to assess its positioning performance under kinematic conditions. A field test was conducted using two Google smartphones on April 7, 2024, in Calgary. We expect to achieve decimeter-level slant ionospheric corrections accuracy compared to geodetic receiver with the two correction models used. Additionally, the positioning accuracy is expected to approach that of PPP-RTK results using geodetic receivers as base stations, significantly outperforming float PPP.

How to cite: Zhang, Y., Jiang, Y., and Gao, Y.: Evaluation of the ionospheric corrections generated by smartphone and application to PPP-RTK, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14897, https://doi.org/10.5194/egusphere-egu25-14897, 2025.

The increasing availability and affordability of low-cost Global Navigation Satellite System (GNSS) systems have made them a viable alternative for various geospatial applications. However, their performance and positioning accuracy require rigorous evaluation, especially when compared to geodetic-grade GNSS systems. This study investigates the accuracy of low-cost GNSS systems in positioning by comparing their results with those obtained from high-precision geodetic GNSS systems.

To evaluate the performance of low-cost GNSS systems, campaign type GNSS measurements were conducted at four points using both low-cost and geodetic GNSS systems. The collected data were processed using the Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP) and the AUSPOS relative positioning services. The positioning results from these services were analyzed to assess the performance of low-cost GNSS systems relative to their geodetic counterparts. Preliminary findings indicate that low-cost GNSS systems exhibit promising accuracy levels in comparison to geodetic systems. The results highlight the potential and limitations of low-cost GNSS technology for scientific and practical applications.

This study contributes to the growing body of knowledge on low-cost GNSS technologies and provides insights into their applicability in fields such as tectonic monitoring and geodetic research. Future work will focus on refining processing techniques to further enhance the reliability of low-cost GNSS systems.

How to cite: Akpinar, B., Aydin, C., Özarpacı, S., Aykut, N. O., Özdemir, A., Oku Topal, G., Güneş, Ö., Karabulut, F., Ayruk, E. T., Çetinkaya, H., Turğut, M., Beytut, B. B., and Doğan, U.: Positioning Accuracy of Low-Cost GNSS Systems: A Comparative Study with Geodetic Solutions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19213, https://doi.org/10.5194/egusphere-egu25-19213, 2025.