This session aims to showcase novel applications of methods from the field of artificial intelligence and machine learning in geodesy.

In recent years, the exponential growth of geodetic data from various observation techniques has created challenges and opportunities. Innovative approaches are required to efficiently handle and harness the vast amount of geodetic data available nowadays for scientific purposes, for example when dealing with “big data” from Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR). Likewise, numerical weather models and other environmental models important for geodesy come with ever-growing resolutions and dimensions. Strategies and methodologies from the fields of artificial intelligence and machine learning have shown great potential not only in this context but also when applied to more limited data sets to solve complex non-linear problems in geodesy.

We invite contributions related to various aspects of applying methods from artificial intelligence and machine learning (including both shallow and deep learning techniques) to geodetic problems and data sets. We welcome investigations related to (but not limited to): more efficient and automated processing of geodetic data, pattern and anomaly detection in geodetic time series, images or higher-dimensional data sets, improved predictions of geodetic parameters, such as Earth orientation or atmospheric parameters into the future, combination and extraction of information from multiple inhomogeneous data sets (multi-temporal, multi-sensor, multi-modal fusion), feature selection and sensitivity, downscaling geodetic data, and improvements of large-scale simulations. We strongly encourage contributions that address crucial aspects of uncertainty quantification and integration of physical relationships into data-driven frameworks. Moreover, addressing reproducibility, interpretability and explainability of machine learning outcomes is certainly fundamental for ensuring scientific rigorousness of novel AI-based solutions.

By combining the power of artificial intelligence with geodetic science, we aim to open new horizons in our understanding of Earth's dynamic geophysical processes. Join us in this session to explore how the fusion of physics and machine learning promises advantages in generalization, consistency, and extrapolation, ultimately advancing the frontiers of geodesy.

Remarkable advances over recent years prove that geodesy today develops under a broad spectrum of interactions, including theory, science, engineering, technology, observations, and practice-oriented services. Geodetic science accumulates significant results in studies towards classical geodetic problems and problems that only emerged or gained new interest, in many cases due to synergistic activities in geodesy and tremendous advances in the instrumentations and computational tools. In-depth studies progressed in parallel with investigations that led to a broadening of the traditional core of geodesy. The scope of the session is conceived with a certain degree of freedom, even though the session intends to provide a forum for all investigations and results of a theoretical and methodological nature.
Within this concept, we seek contributions concerning problems of reference frames, gravity field, geodynamics, and positioning, but also studies surpassing the frontiers of these topics. We invite presentations discussing analytical and numerical methods in solving geodetic problems, advances in mathematical modelling and statistical concepts, or the use of high-performance facilities. Demonstrations of mathematical and physical research directly motivated by geodetic practice and ties to other disciplines are welcome. In parallel to theory-oriented results, examinations of novel data-processing methods in various branches of geodetic science and practice are also acceptable.

Geodetic research produces important contributions that are essential for understanding the dynamics of the Earth. However, the path from research results to policy impact is often challenging. Essential Geodetic Variables (EGVs) were developed to help promote geodetic products and their importance for global society, offering a structured way to identify, share, and communicate key components of geodesy. Furthermore, a classification as EGV should also be an incentive for operational monitoring and the provision of base funding. But how do we make sure that EGVs are not just useful within the scientific community, but also accessible and relevant to policymakers and other stakeholders?
This session will provide an overview of the latest developments in defining the EGVs and draw lessons from other scientific disciplines on how they communicated their essential variables to scientists and stakeholders. We will have an open discussion and hear from experts at the interface of science and policy to explore strategies for making geodetic products and data easier to understand. By the end of the session, we aim to outline specific ways the community can use the EGVs to streamline communication and enhance the visibility of geodetic research.

The Global Geodetic Observing System (GGOS) is an international collaboration of geodetic services and experts working together to provide geodetic data and products that serve science and society beyond the traditional task of measuring and mapping the Earth's surface. GGOS integrates ground- and space-based geodetic observations in order to monitor the Earth's time-variable shape, rotation and gravity. Changes to these characteristics are inherently related to interactions within and between the various components of the Earth system, demonstrating the importance of geodesy in monitoring the changing Earth. To advance our understanding of the underlying processes, the accuracy of geodetic measurements must be one to two levels higher than the magnitude of the changes to be detected. Examples of particularly demanding applications of geodetic measurements include mass transport across the Earth's spheres, the effects of climate change, and geohazards. This session is a forum for discussing ongoing and planned improvements to observing systems for the Earth's geometry, gravity, and rotation, particularly those that envisage the application of new methods and technologies, such as relativistic geodesy, quantum sensors, next generation lasers, PNT based on LEO satellites, etc. We also welcome general contributions on GGOS, including progress reports and plans for the next generation of geodetic observatories integrating measurements of the Earth's geometry, gravimetry, and rotation.

A global Terrestrial Reference Frame (TRF) is fundamental for monitoring the Earth's rotation in space, and to many Earth science applications that need absolute positioning and precise orbit determination of near-Earth satellites. An accurate and stable TRF is especially needed for the quantification of global change phenomena such as sea level rise, current ice melting, tectonic, and seismic deformations. This session generally welcomes contributions on the computation, the evaluation and the use of TRFs.

The computation of TRFs relies on space geodetic observations acquired by ground networks of stations and requires the estimation of a large number of parameters including station positions and Earth Orientation Parameters. Nowadays, measurement biases and imperfect background models are the main factors limiting the accuracy of TRFs. This session therefore welcomes contributions that develop strategies to overcome systematics in space geodetic observing systems such as long-term mean range biases in SLR observations, gravitational deformation of VLBI antennas, GNSS antenna phase patterns, etc.

The second objective of this session is to bring together contributions from individual technique services, space geodetic data analysts, ITRS combination centers and TRF users to discuss the TRF solutions produced by different groups, with a special focus on their comparison, evaluation and updates. The understanding of the discrepancies between the terrestrial scale observed by the different space geodetic techniques, the determination of new local tie vectors at co-location sites, the improvement of geocentre motion determination and the assessment of observed non-linear station motions by comparison with geophysical deformation models are of particular interest.

Papers on the exploitation of past ITRF solutions and the latest 2020 solution updates are of course welcome, as well as presentations regarding any type of development that could improve future TRF solutions. With the development of the GENESIS mission, any contributions on the handling and the impact of co-located instruments of individual techniques onboard satellite missions (space ties) for TRF realization are strongly encouraged. Contributions concerning TRF construction strategies based on combination at the observation level are also welcome.

In recent years, we have observed steady progress in signals, services, and satellite deployment of Global Navigation Satellite Systems (GNSS). Consequently, modernizing and developing GNSS constellations have moved us towards an era of multi-constellation and multi-frequency GNSS signal availability. Also, the deployment of LEO constellations brings opportunities for LEO-augmented PNT services and applications, which, however, forces revisiting the existing and developing novel processing algorithms when fusing LEO and GNSS. Meanwhile, the technology development provided high-grade GNSS user receivers to collect high-rate, low-noise, and multipath impact measurements. Also, recent extraordinary progress in low-cost GNSS chipsets, smartphones, and sensor fusion must be acknowledged. Such advancements boost GNSS research and catalyze an expansion of satellite navigation to novel areas of science and industry. On one side, the developments stimulate a broad range of new GNSS applications. On the other side, they result in new challenges in data processing. Hence, algorithmic advancements are needed to address the opportunities and challenges in enhancing high-precision GNSS applications' accuracy, availability, interoperability, and integrity.
This session is a forum to discuss advances in high-precision GNSS algorithms and their applications in geosciences such as geodesy, geodynamics, seismology, tsunamis, ionosphere, troposphere, etc.
We encourage but do not limit submissions related to:
- GNSS processing algorithms,
- Multi-GNSS benefits for Geosciences,
- Multi-constellation GNSS processing and product standards,
- High-rate GNSS,
- Low-cost receiver and smartphone GNSS observations for precise positioning, navigation, and geoscience applications,
- LEO-augmented precise positioning and quality control,
- LEO observations modeling and processing algorithms,
- Precise Point Positioning (PPP, PPP-RTK) and Real Time Kinematic (RTK),
- GNSS and other sensors (accelerometers, INS, etc.) fusion,
- GNSS products for high-precision applications (orbits, clocks, uncalibrated phase delays, inter-system and inter-frequency biases, etc.),
- Troposphere and ionosphere modeling and sounding with GNSS,
- CORS services for Geosciences (GBAS, Network-RTK, etc.),
- Precise Positioning of EOS platforms,
- GNSS for natural hazards prevention,
- Monitoring crustal deformation and the seismic cycle of active faults,
- GNSS and early-warning systems,
- GNSS reflectometry.

Precise orbit determination is of central importance for many applications of geodesy and earth science. The challenge is to determine satellite orbits in an absolute sense at the centimeter or even sub-centimeter level, and at the millimeter or even sub-millimeter level in a relative sense. Four constellations of GNSS satellites are available and numerous position-critical missions (e.g. altimetry, gravity, SAR and SLR missions) are currently in orbit. Altogether, outstanding data are available offering new opportunities to push orbit determination to the limit and to explore new applications.

This session aims to make accessible the technical challenges of orbit determination and modelling to the wider community and to quantify the nature of the impact of dynamics errors on the various applications.
Contributions are solicited from, but not limited to, the following
areas: (1) precise orbit determination and validation; (2) satellite surface force modelling; (3) advances in modelling atmospheric density and in atmospheric gravity; (4) advances in modelling earth radiation fluxes and their interaction with space vehicles; (5) analysis of changes in geodetic parameters/earth models resulting from improved force modelling/orbit determination methods; (6) improvements in observable modelling for all tracking systems, e.g. SLR, DORIS, GNSS and their impact on orbit determination; (7) advances in combining the different tracking systems for orbit determination; (8) the impact of improved clock modelling methods/space clocks on precise orbit determination; (9) advances in modelling satellite attitude; (10) simulation studies for the planned co-location of geodetic techniques in space mission GENESIS.

GNSS Interferometric Reflectometry (GNSS-IR) is an emerging ground-based remote sensing technique that uses the interference between direct and coherently reflected GNSS signals. This technique has been applied to measure a variety of variables including water level, significant wave height, snow accumulation, ice freeboard, permafrost melt, soil moisture, vegetation water content and coastal subsidence. As the community of GNSS-IR developers and users continues to grow, this session seeks to highlight advances in the (near real-time) acquisition, processing, analysis and application of GNSS-IR in environmental sensing. The session welcomes contributions on algorithmic and technical improvement of GNSS-IR models, as well as the development of open-source hardware and software. We also invite presentations on GNSS-IR data products and their validation, the optimal exploitation of geodetic and affordable GNSS sensors for GNSS-IR applications and initiatives for (near) real-time monitoring of environmental variables.

The precise positioning at centimeter level with GPS has been available for decades, which is lately strengthened by the emerging Global Navigation Satellite Systems (GNSS), such as the European Galileo, Chinese BeiDou, and Russian GLONASS, making positioning cost-effective and compact. OEM boards of various qualities and single-board microcontrollers allow construction of low-cost/mass-market/consumer-grade GNSS receivers that are used for applications requiring precise positioning, sensor synchronisation, GNSS reflectometry, phase time delay and signal attenuation. These applications are spread over fields such as geodesy, hydrology, (hydro-)meteorology, volcanology, natural hazards, cryospheric and biospheric sciences and (urban) navigation. Moreover, they are valuable for deriving and monitoring geophysical phenomena such as sea-level rise, crustal or surface deformation. With these diverse applications low-cost GNSS technology has the ability to bring societal transformations through citizen science and by making geodesy affordable. We solicit abstracts on instrumentation and innovative applications in different fields of research, as well as algorithms, and sensor calibration and integration. We welcome any other contributions that highlight the challenges of using low-cost GNSS receivers and antennas including the socio-cultural aspects.

This session invites innovative Earth system and climate studies employing geodetic observations and methods. Modern geodetic observing systems have been instrumental in studying a wide range of changes in the Earth’s solid and fluid layers at various spatiotemporal scales. These changes are related to surface processes such as glacial isostatic adjustment, the terrestrial water cycle, ocean dynamics, and ice-mass balance, which are primarily due to changes in the climate. To understand the Earth system response to natural climate variability and anthropogenic climate change, different time spans of observations need to be cross-compared and combined with several other datasets and model outputs. Geodetic observables are also often compared with geophysical models, which helps in explaining observations, evaluating simulations, and finally merging measurements and numerical models via data assimilation.

We look forward to contributions that:
1. Utilize geodetic data from diverse geodetic satellites, including altimetry, gravimetry (CHAMP, GRACE, GOCE, and GRACE-FO, SWOT), navigation satellite systems (GNSS and DORIS) or remote sensing techniques that are based on both passive (i.e., optical and hyperspectral) and active (i.e., SAR, Sentinel, NISAR) instruments.
2. Cover a wide variety of applications of geodetic measurements and their combination to observe and model Earth system signals in hydrological, ocean, atmospheric, climate, and cryospheric sciences.
3. Show a new approach or method for separating and interpreting the variety of geophysical signals in our Earth system and combining various observations to improve spatio-temporal resolution of Earth observation products.
4. Work on simulations of future satellite missions (such as MAGIC and NGMM) that may advance climate sciences.
5. Work towards any of the goals of the Inter-Commission Committee on "Geodesy for Climate Research" (ICCC) of the International Association of Geodesy (IAG).

We are committed to promoting gender balance and ECS in our session. With the author consent, highlights from this session will be shared on social media with a dedicated hashtag during the conference in order to increase the impact of the session.

The growth and decay of large ice sheets on the Earth's surface during the past, present and future leads to Glacial isostatic adjustment (GIA) triggered by the redistribution of surface ice and ocean masses, and the flow of mantle rocks. It involves radial and tangential motion, changes in sea levels, the Earth's gravity field and rotational motion, lithospheric bending and the state of stress inside the Earth. Although this process is primarily driven by ice-sheet dynamics and Earth's structure, it impacts other Earth systems like the cryosphere and hydrosphere. GIA controls relative sea-level change through vertical land motion and gravitational–rotational effects, making it fundamental for ocean sciences, hydrological sciences, and climate investigations. Furthermore, differential uplift and tilting due to GIA reshapes landscapes and drainage networks, while emergent land and basin connections drive ecosystem succession and carbon burial. GIA-related stress redistribution influences a region’s seismicity and its seismic hazard, which must be considered in nuclear waste storage safety assessments. Similarly, such stress changes can alter volcanic activity even thousands of kilometres away from the glaciated area. GIA effects are present in a wealth of standardized observational data, such as GNSS measurements, tide gauges, relative sea levels, and terrestrial and satellite gravimetry. These data help refine GIA models, which enhance our understanding of ice-sheet history, sea-level changes, Earth's rheology and near-surface processes. The GIA theory can also be applied to study other planets such as Mars.

We welcome contributions on GIA's effects across various scales, including geodetic measurements, complex GIA modelling, GIA-induced sea-level changes, the Earth's response to current ice-mass changes, and overview on emerging GIA data collections. We also invite abstracts on GIA's impact on nuclear waste sites, volcanism, groundwater, permafrost, and carbon resources. We especially appreciate new model developments in local, high spatial and temporal resolution for GIA assessments, results of fully coupled ice dynamics-GIA models, studies of broader environmental relevance, and improved GIA corrections for other geoscientific fields.

Advancements in geodetic technologies across space, land, and marine domains have significantly enhanced our ability to observe, model, and understand lithospheric processes and associated geohazards. Space-based geodetic methods, like dense GNSS networks, high-resolution InSAR imaging, and innovative seafloor geodesy techniques (such as pressure sensing, acoustic ranging, fiber optic strain cables and GNSS-Acoustic positioning) provide continuous and spatially extensive datasets across large regions of the Earth, significantly broadening the scope of geoscience applications.
These technologies provide critical insights into the geodynamics of lithospheric plates and enable the detailed characterization of both interplate and intraplate tectonic domains, illuminating complex tectonic processes that govern seismicity and crustal strain. Furthermore, the synergy between different geodetic platforms supports real-time hazard assessment and early warning systems for earthquakes, tsunamis, and volcanic eruptions. This multidimensional approach enhances both scientific understanding of Earth’s dynamic behavior and societal resilience by informing evidence-based disaster risk reduction strategies.
This session invites contributions employing geodetic, geophysical, geological, and seismotectonic data to investigate active deformation zones, including intraplate volcanic settings. We especially welcome interdisciplinary studies that integrate geodesy, seismology, tectonics, and geophysics to better constrain strain accumulation, plate motions, and lithospheric deformation. The overarching goal is to highlight recent geodetic advances and explore their implications for understanding lithospheric geodynamics and enhancing hazard preparedness.

Global mass transport processes are increasingly important to measure and understand, and mass variations may be changing with climate change. Both cryospheric change and terrestrial hydrologic processes are important, to different degrees in different climate zones. Global models for cryospheric and hydrologic processes are becoming more mature, but models usually are not yet unified: cryospheric change estimates may not specify where the water goes, and terrestrial hydrological models do not account for cryospheric changes well. The impacts of mass transport are readily measurable using geodesy (e.g., gravity change and Earth deformation), and variations in mass transport may now be a limiting error source on geodetic observables.
This session aims at bringing together researchers from the cryosphere, hydrosphere and geodetic community with the goal of improving geophysical models. We invite contributions incorporating global or regional cryospheric observations and models, as well as efforts that integrate cryospheric change with other terrestrial water storage models. Furthermore, we welcome comparisons of cryospheric or hydrologic models with geodetic observations and studies that aim to disentangle cryospheric and hydrologic signals. We also look for investigations that exploit mutual benefits of improving mass transport modeling and a better understanding of geodetic observables (e.g., implications on geodetic reference frame, and integrative measures like geocenter).

The redistribution of geophysical fluids across the Earth’s surface and near surface driven by water cycle dynamics and its extremes can cause measurable load-induced deformation. In the last decades, increasingly accurate and available space geodetic measurement techniques (among others GNSS, InSAR, satellite gravimetry and altimetry) have enriched our understanding of this response. Accurate observations of crustal deformation together with geophysical models can be applied to quantify the hydrological loads, and through that, they provide new insight into the related hydrological processes. This session aims to attract research that further advances our ability to accurately quantify hydrological mass loads across different temporal and spatial scales, and involving different hydrological compartments (e.g., groundwater, surface water, snow, ice). We invite studies focusing on innovative measurement and modeling approaches and reconciling observations from different geodetic measurement techniques used to study hydrological loading. Research that assesses the strengths and limitations of each approach and that proposes strategies for a seamless and accurate integration is highly encouraged. Additionally, we seek studies that conduct intercomparisons of different hydrological model data (land surface, hydrological models) and geodetic measurement techniques to understand their relative strengths, weaknesses, and accuracies.

Global Navigation Satellite Systems (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) are both very well established approaches for measuring tectonic and volcanic activity. Over recent years, improvements in data quality, the automation of processing pipelines, cheaper measurement hardware, and cheaper computation has put our research community on the brink of complete surveillance of surface motions – a situation in which, for some regions, we will be able to map every actively slipping fault and actively deforming volcanic zone, more easily identify areas of heightened stress accumulation, and automatically report when surface motions accelerate.

In this session we would like to foster an exchange of ideas and experiences about how to best continue towards this state of surveillance. In particular, we would like to explore how the GNSS, InSAR, and tectonic- and volcanic- modelling communities can work together in the coming years to extract the most value from our continued installation, processing, and interpretation efforts. How many stations will we need? Do we have enough data? What experiments and simulations should we prioritise? What are the economic (personnel, computation, satellites, natural disasters), sustainability, and strategy (e.g. centralisation vs. decentralisation) considerations?

We invite scientists and related stakeholders from our communities to come together to share their work on full value extraction of our GNSS and InSAR data. Whether you want to present some case study of a certain region, or you want to present some analysis at a larger spatial and computational scale, we welcome you to the discussion.

Accurate modeling and prediction of Earth rotation is important for numerous applications in geodesy, astronomy and navigation. In recent years, geodetic observation systems have made significant progress in monitoring the temporal variability of the Earth's rotation, which is largely related to dynamic processes in the planet's fluid components. The increase in observation accuracy must go along with the improvement of theories and models.
We welcome contributions that highlight new determinations and analyses of Earth Orientation Parameters (EOP), including combinations of different geodetic and astrometric observational techniques for deriving UT1/length-of-day variations and polar motion. We welcome discussions of EOP solutions in conjunction with a consistent determination of terrestrial and celestial frames. We are interested in the latest achievements in EOP forecasting, especially reports exploring the potential of innovative techniques, such as machine learning, in improving forecast accuracy.
We invite contributions on the dynamical links between Earth rotation, geophysical fluids, and other geodetic quantities, such as the Earth gravity field or surface deformation, and of explanations for the physical excitations of Earth rotation. Besides tidal influences from outside the Earth, the principal causes for variable EOP appear to be related to angular momentum exchange from motions and mass redistribution of the fluid portions of the planet.
We welcome contributions about the relationship between EOP variability and the variability in fluids due to climate effects or global change. Forecasts of these impacts are important especially for the operational determination of EOP, and the effort to improve predictions is an important topic.
We are interested in the progress in the theory of Earth rotation. We seek contributions that are consistent internally with the accurate observations at the mm-level, to meet the requirements of the Global Geodetic Observing System and respond to IAG 2019 Res. 5 and IAU 2021 Res. B2, as well as those derived from the research of current IAU/IAG/IERS working groups on these topics. We also welcome contributions on the variability and excitation of the rotation of other planetary bodies.

Recent developments in different fields have enabled new applications and concepts in the space- and ground-based observation of the Earth’s gravity field. In this session, we discuss the benefit of new sensors and techniques and their ability to provide precise and accurate measurements of Earth’s gravity.
We encourage the dissemination of results from geoscience applications of absolute quantum gravimeters, which are gradually replacing devices based on the free-fall of corner cubes, since they allow nearly continuous absolute gravity measurements and offer the possibility to measure the gravity gradient. Quantum sensors are also increasingly considered for future gravity space missions. In addition, we welcome results from gravimeters based on other technologies (e.g., MEMS or superconducting gravimeters) that have been used to study the redistributions of subsurface fluid masses (water, magma, hydrocarbons, etc.) in permanent deployment or field surveys.
Besides gravimeters, other concepts can provide unique information on the Earth’s gravity field. According to Einstein’s theory of general relativity, frequency comparisons of highly precise optical clocks connected by optical links give direct access to differences of the gravity potential (relativistic geodesy) over long baselines. In future, precise optical clock networks can be applied for defining and realizing a new international height system or to monitor mass variations.
Laser interferometry between test masses in space with nanometer accuracy – successfully demonstrated through the GRACE-FO mission – also belongs to these novel concepts, and even more refined concepts (tracking swarms of satellites, space gradiometry) will be realized in the near future.
We invite presentations illustrating the state of the art of those novel techniques, that will open the door to a vast bundle of applications, including the gravimetric observation of the Earth-Moon system with high spatial-temporal resolution as well as the assessment of terrestrial mass redistributions, occurring at different space and time scales and providing unique information on the processes behind, e.g., climate change and volcanic activity.
This session is organized jointly with the IAG (International Association of Geodesy) project "Novel Sensors and Quantum Technology for Geodesy (QuGe)" and the Horizon Europe project EQUIP-G (Grant ID 101215427).

For more than two decades, satellite missions dedicated to the determination of the Earth's gravity field have enabled a wide variety of studies related to climate research as well as other geophysical or geodetic applications. Continuing the successful, more than 15 years long data record of the Gravity Recovery and Climate Experiment (GRACE, 2002-2017) mission, its Follow-on mission GRACE-FO, launched in May 2018, is currently in orbit providing fundamental observations to monitor global gravity variations from space. Regarding the computation of high-resolution static gravity field models of the Earth and oceanic applications, the Gravity field and steady-state Ocean Circulation Explorer (GOCE, 2009-2013) mission plays an indispensable role. Complementary to these dedicated missions, observations from other non-dedicated missions such as Swarm as well as satellite laser ranging (SLR) have shown to be of significant importance, either to bridge gaps in the GRACE/GRACE-FO time series or to improve gravity field models and scientific results derived thereof. The important role of satellite gravimetry in monitoring the Earth from space has led to various ongoing initiatives preparing for future gravity missions, including simulation studies, the definition of user and mission requirements and the investigation of potential measurement equipment and orbit scenarios.

This session solicits contributions about:
(1) Results from satellite gravimetry missions as well as from non-dedicated satellite missions in terms of
- data analyses to retrieve time-variable and static global gravity field models,
- combination synergies, and
- Earth science applications.
(2) The status and study results for future gravity field missions.

The Global Geodetic Observing System (GGOS) Focus Area on Geodetic Space Weather Research (GSWR) of the International Association of Geodesy (IAG) invites researchers to explore the critical role of geodetic techniques in advancing our understanding of space weather dynamics. This session aims to bring together scientists and researchers to discuss modelling methodologies and accuracy of space-based observations for advancing the accuracy and resilience of space weather modeling, monitoring, and forecasts. Emphasis is placed on the use of geodetic observations (e.g., GNSS, GNSS-RO, VLBI, DORIS, InSAR) to provide insights into the ionosphere, plasmasphere, and thermosphere.

This session will explore recent advancements in total electron content (TEC) estimation and prediction, in three-dimensional ionospheric modelling techniques such as tomography, in using data assimilation and machine learning techniques, in electron density retrieval from recent GNSS radio-occultation missions, and ionospheric scintillation impacts on GNSS data. We also encourage studies assessing the impacts of atmospheric drag on low Earth orbit (LEO) satellites, aiming to improve neutral density estimation within the thermosphere through precise orbit determination (POD) and high-resolution accelerometer observations. Additionally, we welcome contributions on monitoring and forecasting space weather events through geodetic observations and modelling, including but not limited to geomagnetic storms, ionospheric plasma bubbles, and traveling ionospheric disturbances. Discussions on the implications of these space weather phenomena for positioning and navigation systems are also encouraged. We also welcome the integration of geodetic observations with data from dedicated instruments, such as ionosondes, in-situ Langmuir probes, and incoherent scatter radars.

Geodesy contributes to atmospheric science by providing some of the essential climate variables of the Global Climate Observing System. Water vapor is currently under-sampled in meteorological and climate observing systems. Thus, obtaining more high-quality humidity observations is essential for weather forecasting and climate monitoring. The production, exploitation, and evaluation of operational GNSS Meteorology for weather forecasting is well established in Europe thanks to a long-lasting cooperation between the geodetic community and the meteorological services. Improving the skill of numerical weather prediction (NWP) models, e.g., to forecast extreme precipitation, requires GNSS products with higher spatio-temporal resolution and shorter turnaround. Homogeneously reprocessed GNSS data (e.g., IGS repro3) have high potential for monitoring water vapor climatic trends and variability. Advances in SLR atmospheric delay modelling are using NWP data and 3D ray-tracing to improve tropospheric corrections. With shorter orbit repeat periods, SAR measurements are a source of information to improve NWP models. Additionally, emerging LEO-PNT missions offer capabilities for atmospheric and environmental monitoring due to their dense geometry, rapid revisit times and new signals that will be defined. Their integration with GNSS and other geodetic techniques could open new possibilities for real-time correction models. Reflected signals of GNSS and future LEO-PNT provide additional opportunities for remote sensing of the Earth system. GNSS-R contributes to environmental monitoring with estimates of soil moisture, snow depth, ocean wind speed, sea ice concentration and can be used to retrieve near-surface water vapor. We welcome, but do not limit, contributions on:
-Estimates of the neutral atmosphere using ground- and space-based geodetic data
-Retrieval and comparison of tropospheric parameters from multi-GNSS, VLBI, DORIS and multi-sensor observations
-Nowcasting, forecasting, and climate research using RT and repro tropospheric products, employing NWP and machine learning
-Assimilation of GNSS tropospheric products in NWP and in climate reanalysis
-Production of SAR tropospheric parameters and assimilation in NWP
-Homogenization of long-term GNSS, VLBI tropospheric products
-Detection and characterization of sea level, snow depth, and sea ice changes, using GNSS-R
-Monitoring of soil moisture and ground-atmosphere boundary interactions using GNSS data

In this session we search for contributions of general interest for the geodesy community which fall outside the scope of the other sessions. Contributions can cover theoretical aspects to practical or experimental nature.

Get to know the basics of geodesy and the types of data it provides. From GNSS signals to gravity measurements, geodetic observations play an important role in Earth sciences by supporting research in various disciplines (e.g., hydrology, glaciology, geodynamics, oceanography, seismology). This short course will give you an introduction to what geodesy can (and can’t) tell us. You don’t need to be a geodesist to join and by the end, you won’t be an expert either, but we do hope that you have gained more knowledge about the limitations as well as advantages of geodetic data. The crash course is designed and taught by scientists from the Geodesy division, and open to anyone curious about how geodesists work as well as for researchers already handling geodetic data. We hope to have a lively discussion during the short course. And if you’re a geodesist, this is your chance to hear directly what scientists from other disciplines need when working with your data.

The advances in geodetic theory made an increased emphasis on mathematical methods necessary (Heiskanen and Moritz, 1956). For several decades a rigorous mathematical framework has been developed - Gauss/Markov BLUE, MLE, DIA - in the context of parameter estimation and statistical testing, thus paving the way for a better understanding of Earth's shape, orientation in space, and gravity field. With the introduction of machine learning, the focus has been shifted from a model-driven to a data-driven approach, also thanks to the large amount of data made available through several different terrestrial and space techniques (e.g. GNSS, InSAR, VLBI, SLR, Altimetry, Gravimetry, etc.).

In this short course we first provide a broad overview of geodetic theory, addressing different mathematical problems and well-established solutions adopted in Geodesy. Therefore, we highlight gaps in the current theoretical framework and introduce machine/deep learning paradigms as potential alternative to classical solutions. In this way, we further discuss key relationships between statistical learning and ML/DL methods, in particular focusing on fundamental issues in the adoption of AI techniques as "black box" solutions. Hence, we provide a clear understanding of the major pitfalls, especially concerning the quantification of uncertainty and confidence levels for ML/DL solutions.

Ultimately, we highlight the key role in science of 'explainability' and 'reproducibility', both often overlooked when adopting AI techniques in Geodesy. Target audience is Geodesy and Earth-science practitioners who deploy or evaluate ML in their research works. The suggested format is 60 minutes (e.g. lunch slot) with 30′ for a mini lecture on theoretical fundamentals, 20′ live demo with relevant geodetic examples, and 10′ for Q&A.

Prerequisites: basic linear algebra; no prior ML/DL knowledge is required.

This session focuses on the hydrogeodetic measurement of water bodies such as rivers, lakes, floodplains and wetlands, groundwater and soil. The measurements relate to estimating water levels, extent, storage and discharge of water bodies through the combined use of remote sensing and in situ measurements and their assimilation in hydrodynamic models.

Monitoring these resources plays a key role in assessing water resources, understanding water dynamics, characterising and mitigating water-related risks and enabling integrated management of water resources and aquatic ecosystems. While in situ measurement networks play a central role in the monitoring effort, remote sensing techniques provide near real-time measurements and long homogeneous time series to study the impact of climate change from local to regional and global scales.

During the past three decades, a large number of satellites and sensors has been developed and launched, allowing to quantify and monitor the extent of open water bodies (passive and active microwave, optical), the water levels (radar and laser altimetry), the global water storage and its changes (variable gravity). River discharge, a key variable of hydrological dynamics, can be estimated by combining space/in situ observations and modelling, although still challenging with available spaceborne techniques. Interferometric Synthetic Aperture Radar (InSAR) is also commonly used to understand wetland connectivity, floodplain dynamics and surface water level changes, with more complex stacking processes to study the relationship between ground deformation and changes in groundwater, permafrost or soil moisture.

Traditional instruments contribute to long-term water level monitoring and provide baseline databases. Scientific applications of more complex technologies like Synthetic Aperture Radar (SAR) altimetry on CryoSat-2, Sentinel-3A/B and Sentinel-6MF missions are maturing, including the Fully-Focused SAR technique offering very-high along-track resolution. The SWOT mission, now opens up many new hydrology-related opportunities. We also welcome submissions of pre-launch studies for CRISTAL, Sentinel-3C/3D/3NG-Topography, Sentinel-6NG, MAGIC/NGGM and and other proposed missions such as Guanlan, HY-2 and SmallSat constellations such as the SMASH concept now called H2R, and covering forecasting.

Fibre optic based techniques allow probing highly precise point and distributed sensing of the full ground motion wave-field including translation, rotation and strain, as well as environmental parameters such as temperature at a scale and to an extent previously unattainable with conventional geophysical sensors. Considerable improvements in optical and atom interferometry enable new concepts for inertial rotation, translational displacement and acceleration sensing. Laser reflectometry on commercial fibre optic cables allows for the first time spatially dense and temporally continuous sensing of the ocean’s floor, successfully detecting a variety of signals including microseism, local and teleseismic earthquakes, volcanic events, ocean dynamics, etc. Significant breakthrough in the use of fibre optic sensing techniques came from the new ability to interrogate telecommunication cables to high temporal and spatial precision across a wide range of environments. Applications based on this new type of data are numerous, including: seismic source and wave-field characterisation with single point observations in harsh environments such as active volcanoes and the seafloor, seismic ambient noise interferometry, earthquake and tsunami early warning, and infrastructure stability monitoring.

We welcome contributions on developments in instrumental and theoretical advances, applications and processing with fibre optic point and/or distributed multi-sensing techniques, light polarization and transmission analyses, using standard telecommunication and/or engineered fibre cables. We seek studies on theoretical, instrumental, observation and advanced processing across all solid earth fields, including seismology, volcanology, glaciology, geodesy, geophysics, natural hazards, oceanography, urban environment, geothermal applications, laboratory studies, large-scale field tests, planetary exploration, gravitational wave detection, fundamental physics. We encourage contributions on data analysis techniques, novel applications, machine learning, data management, instrumental performance and comparison as well as new experimental, field, laboratory, modelling studies in fibre optic sensing studies.

We are looking for studies that investigate how tectonic plates move, how this movement is accommodated in deformation zones, and how elastic strain builds up and is released along faults and at plate boundaries. These studies should combine space- or sea-floor geodesy with observations like seismicity, geological slip-rates and rakes or sea-level and gravity changes.

How to best reference relative InSAR rate tiles to a plate? How can we infer the likelihood of future earthquakes from elastic strain buildup? How persistent are fault asperities over multiple earthquake cycles? Are paleoseismic fault slip rates identical to those constrained by geodesy? What portion of plate motion results in earthquakes, and where does the rest go? How do mountains grow? How well can we constrain the stresses that drive the observed deformation? How much do the nearly constant velocities of plates vary during the earthquake cycle, and does this influence the definition of Earth's reference frame?

We seek studies using space and sea floor geodetic data that focus on plate motion, deformation zones, and the earthquake cycle. Key questions include earthquake likelihood, fault slip-rates, uplift rates, non-elastic strain, and sea-level changes.

Understanding the processes controlling landslides, earthquakes, volcanic eruptions and tsunamis requires utilizing natural experiments and integrated models to identify and isolate controlling factors. Subduction zone hazards often occur as a

cascading series of events, requiring a system wide and integrative approach to understand. How do climate and tectonics interact to determine the susceptibility to landslides? What is the relative importance of magma supply and crustal faulting in controlling eruptive frequency? Are the size and location of earthquakes affected by structural boundaries? How do cascading sequences of events impact
subduction zone hazards? These and other geohazard questions can be addressed by studying behaviors across subduction zones. We invite contributions that use the power of comparison across multiple subduction zones to develop new insights. SZ4D is a community-driven initiative for a long-term, interdisciplinary research program to define the limits and possibilities of predicting geohazards. Observational, theoretical and laboratory studies comparing the SZ4D focus areas of Cascadia, Alaska and Chile are particularly welcome.

Mantle convection is a fundamental process of the Earth. Direct observations of this process are obtained through a variety of multiscale methods. They may provide constrains to estimate fundamental parameters for the Earth mantle structure (e.g., viscosity, density and temperature). Seismic imaging and gravity data, for instance, provide a snapshot of processes occurring in the present-day mantle. Geochemical analysis of trace elements can be used to estimate temperature and depths of melt generation. Histories of large scale horizontal and vertical lithosphere motion recorded in the stratigraphic data hold important information on the evolving mantle bouyancies. Altogether these classes of observations would provide powerful constraints for geodynamic forward and inverse models of past mantle convection.
This session aims to provide a holistic view of the Earth mantle and their evolution through time. We welcome contributions from seismic tomography, anisotropy studies, geochemistry, plate kinematics, structural geology and theoretical models that address questions surrounding Earth’s mantle an its evolution in the Cretaceous and Cenozoic times. Studies using a multidisciplinary approach are particularly encouraged.

Deciphering the formation and evolution of planetary bodies requires a comprehensive investigation of both their surfaces and internal structures. Seismic data provide the most direct constraints on interiors, but such measurements remain scarce across the Solar System. In their absence, gravity and magnetic field observations have become fundamental for inferring the structure and dynamics of interiors of planetary bodies, spanning the Earth, Moon, and terrestrial planets to giant planets, their moons, and small bodies.
The scientific return of these geophysical datasets is greatly enhanced when combined with complementary surface observations, laboratory experiments, and numerical modeling. Multi-spectral and hyperspectral imaging, together with experimental analyses, link remote sensing data to mineralogical and physical properties, offering insights into the composition of outer and internal layers. Altimetry measurements provide independent constraints on tidal responses and rotational dynamics, complementing gravity and magnetic data and offering key insights into the rheology and differentiation of the deep interior. Joint analyses of gravity and topography provide information regarding the thickness, density, and elastic properties of interior layers, while thermochemical evolution models connect present-day structures through space and time to long-term geophysical and geological processes. Together, these approaches provide a more integrated understanding of how planetary bodies formed, differentiated, and evolved.
This session will focus on the instruments, measurement techniques, modeling approaches, and laboratory studies that enable robust constraints on the evolution of surfaces and interiors of planetary bodies. Contributions are invited that address both achievements and limitations of current methods, as well as innovative strategies to overcome existing challenges or combine disparate methodologies. Results from past, ongoing, and forthcoming missions, integrative analyses across multiple datasets, and forward-looking exploration concepts are all welcome. By bringing together diverse perspectives, the session aims to provide a broad and technically rigorous overview of the methods by which we can infer the processes shaping planetary bodies and to outline pathways for major discoveries in the coming decades.

Are you unsure about how to bring order in the extensive program of the General Assembly? Are you wondering how to tackle this week of science? Are you curious about what EGU and the General Assembly have to offer? Then this is the short course for you!

During this course, we will provide you with tips and tricks on how to handle this large conference and how to make the most out of your week at this year's General Assembly. We'll explain the EGU structure, the difference between EGU and the General Assembly, we will dive into the program groups and we will introduce some key persons that help the Union function.

This is a useful short course for first-time attendees, those who have previously only joined us online, and those who haven’t been to Vienna for a while!

Science is not above any socio- and geopolitical issues; rather it is intertwined with them. Societal and geopolitical conditions deeply affect the choices we make about what research to fund, whose knowledge to value, where and with whom to collaborate, and who can attend a conference. As scientists, especially in the Earth and planetary sciences, we cannot ignore the human and environmental consequences of our work. It is especially a present issue in Earth observation, where the majority of the satellites have dual-use operating for both scientific and military purposes. In many cases, scientific tools have facilitated ecocide, exploitation of land and natural resources under neocolonial structures.

While discussing security and safety is crucial during times of conflict, we also need to be aware of possible risks that securitisation poses on the ethical, social and environmental aspects of scientific work. This is also relevant for disaster and risk management and preparedness which many geoscientists are involved in.

This session invites presentations by individuals and teams that address questions like:

- How should geoscientists conduct research and collaboration in fragile or geopolitically unstable regions?
- How do geopolitical tensions or decisions influence geoscience research and collaboration, and what can geoscientists do about it?
- What are the impacts of political borders and decisions on the functioning of the Earth’s systems? How do they affect how geoscientists study the Earth’s systems?
- What are the roles of scientists, academic institutions as well as Earth science societies like EGU in facilitating international collaboration, and supporting academic advocacy and activism in times of geopolitical instability and tensions?
- What responsibilities do Earth and planetary scientists carry when their research is used to harm people and the environment?
- What other geoethical dilemmas arise in such circumstances, and how can they be resolved?

Examples may include current or past case studies of Earth science research that has:

- prevented or caused situations that escalated into conflicts
- increased transparency about the impact of war on people and places (e.g., InSAR monitoring of building damage)
- historical and current examples of geoscientific knowledge used for resource extraction, such as hydrocarbon, water and critical minerals, and their links to conflict, instability, forced migration, famines and underdevelopment