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.
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.
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.
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.
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 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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
Posters virtual: Thu, 1 May, 14:00–15:45 | vPoster spot 1
EGU25-17154 | ECS | Posters virtual | VPS23
GGOS IberAtlantic Affiliate: Bringing Geodesy Closer to Society across the Iberian Peninsula and the Atlantic regionThu, 01 May, 14:00–15:45 (CEST) | vP1.13
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.
EGU25-19802 | ECS | Posters virtual | VPS23
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.Thu, 01 May, 14:00–15:45 (CEST) | vP1.14
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.
EGU25-20077 | Posters virtual | VPS23
Influence of VLBI Network Geometry on the Estimation of Earth Orientation ParametersThu, 01 May, 14:00–15:45 (CEST) | vP1.15
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.
EGU25-13924 | Posters virtual | VPS23
The Crustal Dynamics Data Information System (CDDIS) Updates for 2025Thu, 01 May, 14:00–15:45 (CEST) | vP1.29
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.
