2024 marks the 162^nd anniversary of the founding of the International Association of Geodesy. In 1862, 15 States agreed to cooperate in a "Central European Arc Measurement" project to observe the shape of the Earth. Besides leading to an improved knowledge of the shape of the Earth, the measurements taken during this project also led to an improved reference frame and geoid for Central Europe. In the course of taking these measurements scientific issues were encountered that also had to be addressed. The spirit of cooperation in both taking operational measurements and conducting scientific research that exists today within the IAG has been a hallmark of the IAG ever since it was founded in 1862.

The dual nature of the IAG, in advancing both observations and science, is reflected in the organizational structure of the IAG. Services are responsible for advancing geodetic observations in their area of expertise; Commissions and Inter-commission Committees are responsible for advancing geodetic science; Projects are incubators for new initiatives; the Communications and Outreach Branch, together with GGOS, is responsible for promoting geodesy to the other sciences and to society at large; and GGOS, the Global Geodetic Observing System, is meant to integrate the diverse geodetic observations into a coherent geodetic imaging system of the Earth as a whole.

One of the strengths of geodesy is its interdisciplinary nature. Geodetic observations contribute to improving our understanding of many different Earth processes, from space weather to core dynamics. This affords the opportunity for geodesists to collaborate with scientists from many different disciplines. Besides the value to science, geodetic data and products are also of great value to society. The International Terrestrial Reference Frame (ITRF) provided by the International Earth Rotation and Reference Systems Service (IERS), one of the 12 Services of the IAG, underpins location-based services like navigation aids on cell phones. By forging collaborations with other organizations, the IAG can ensure that its data and products continue to meet the needs of both its scientific and societal customers.

How to cite: Gross, R.: The International Association of Geodesy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10339, https://doi.org/10.5194/egusphere-egu24-10339, 2024.

The services of the International Association of Geodesy (IAG) provide very important and valuable geodetic data, information, and data products that are increasingly relevant for Earth system research, including monitoring of global change phenomena and a wide range of diverse applications such as satellite navigation, surveying, mapping, engineering, geospatial information systems, and so on.

Currently, it is difficult for many people to obtain an overview of all available geodetic products and data. The Global Geodetic Observing System (GGOS) of the IAG aims to fill this gap by developing the GGOS-Portal (ggos.org/portal), which will serve as a unique search and access point (one-stop shop) for geodetic data and products. Data and products will be described by rich metadata and remain physically located at their originating data centers of each contributing IAG service and other data providers. With this future platform, GGOS will contribute to increase the visibility of geodetic data for scientific research and to make other disciplines and the society aware of geodesy and its beneficial products.

Several software packages are available for the realization of such a metadata platform. Two of them are particularly suitable for this purpose: GeoNetwork and CKAN. Based on the community survey conducted in spring 2023, a requirements profile for the GGOS portal was drawn up as part of a feasibility study and compared with the tested functionalities of the two software packages. A particular focus was on testing the metadata harvesting function.

How to cite: Sehnal, M. and Steiner, L.: GGOS Portal - The future Metadata Platform for Geodetic Data - Feasibility Study and Perspectives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1314, https://doi.org/10.5194/egusphere-egu24-1314, 2024.

As earth observing services and techniques have flourished, data and products have exponentially grown, like the proliferation of GNSS stations capable of providing real-time data, SLR stations shifting to kHz lasers, and VLBI’s implementation of VGOS telescopes.  The CDDIS is continually evolving to fulfill the new storage, quality check, and latency requirements that these changes bring, as well as meet new standards such as the shift toward FAIR and open science.  These have shaped how the CDDIS develops new software and resources.  Beginning next year, the CDDIS will begin to transition their data and products to the AWS cloud, beginning with DORIS data.  This poster will highlight the CDDIS’s recently updated processing system, new data and products available, and future work.

How to cite: Woo, J. and Yates, T.: The CDDIS – Updates and Future Developments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22454, https://doi.org/10.5194/egusphere-egu24-22454, 2024.

The GGOS Bureau of Products and Standards (BPS) supports the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) in its goal to provide highly accurate, consistent, and long-term stable geodetic products needed to monitor, map, and understand changes in the Earth’s shape, rotation, and gravity field. A key objective of the BPS is to keep track and to foster homogenization of adopted geodetic standards and conventions across all IAG components for the generation of geodetic products. This includes the interaction with the IAG Services and other entities that deal with standards and conventions, such as the Conventions Center of the IERS (International Earth Rotation and Reference Systems Service), the Commission A3 ”Fundamental Standards” of the International Astronomical Union (IAU) and the Technical Committee 211 of the International Organization for Standardization (ISO/TC 211).

This contribution presents the structure and role of the BPS. It highlights some of the recent activities, which are focused on the updating the BPS inventory of standards and conventions used for the generation of IAG products, the revision of the IERS Conventions, mainly related to Chapter 1 ”General definitions and numerical standards” as well as the description and promotion of geodetic products published at the GGOS website (www.ggos.org). The BPS also contributes to the generation of GGOS outreach material, such as videos, brochures, social media posts, etc. to make other disciplines and society aware of geodesy and its beneficial products. Finally, planned activities of the BPS according to the new GGOS Strategic Plan 2024-2034 are provided.

How to cite: Angermann, D., Gruber, T., Michael, G., Robert, H., Urs, H., Laura, S., and Peter, S.: GGOS Bureau of Products and Standards: Recent activities and future plans, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10228, https://doi.org/10.5194/egusphere-egu24-10228, 2024.

Since Gauss (1828), the theoretical shape of the Earth has been defined as a distinct potential surface of the gravity field that best fits the sea level at rest. The gravity field is described as a sum of spherical function series whose coefficients are calculated from satellite and in situ gravity measurements. Sea levels have been measured in harbours since the 18th century using mareographs, and are now often supplemented by data from nearby GNSS stations.

In our work, we developed a program to determine the potential value for a given height from mareograph data. This allows us to use the data available from the stations to determine what this value was in an earlier period as well. Furthermore, if more than one dataset is available for a particular sea segment, the average value for that sea over a certain period can be given.

We tested the method in the Japanese Sea, where we had data from 9 stations. These were averaged every 5 years and the resulting data were used to calculate the potential values, as well as the average value for the sea segment for the latest period 2016-2020. In the future, we plan to use this method to perform such calculations for more sites, which would also provide information on the effects of tectonics and global sea level change.

Gauss, C. F. (1828) Bestimmung des Breitenunterschiedes zwischen den Sternwarten von Göttingen und Altona. Vandenhoeck und Ruprecht, Göttingen, 84 p.

Supported by the ÚNKP-23-1 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund.

How to cite: Cziraki, K. and Timár, G.: Estimation of the potential value of given sea segments for certain time periods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-584, https://doi.org/10.5194/egusphere-egu24-584, 2024.

Geometric and gravimetric measurements both have proven to be robust approaches to analyzing sea level changes. The relationship between them is also worth exploring. In this research, the geometric signal and gravimetric signal as well as volume variations in Baltic Sea are compared during the period from 2002.4 to 2016.12. Ideally, the geometric signal should be the sum of gravimetric signal and volume variations, which is so-called sea-level budget. Here, the geometric signal is selected as altimetric data from multi missions combined with in-situ observations from tide gauges. The Mascon solutions are used as gravimetric signals while the volume variations are represented by steric height derived from Baltic Sea Physics Reanalysis model. The Baltic Sea is divided into four regions and the sea level budget equation is applied in each region. The results reveal the gravimetric and volume components exhibit satisfying correlations with geometric signals, which are larger than 0.85 in all four regions. The north region has the least correlation due to the sea ice problem. Furthermore, the comparison underscores the dominance of the gravimetric signal, contributing to approximately 90% of the total sea level change. On the other hand, the sea level trend is estimated by both geometric signal and the sum of gravimetric and volume components. The difference between the two trends in each region is mainly caused by ocean bottom deformation, primarily influenced by glacier isostatic adjustment (GIA). In the processing of mason, the GIA effect is already removed but the geometric signal contains ocean bottom deformation. Therefore, it is necessary to consider the land deformation during the trend comparison. However, because of the sea level equation, the sea level does not change as much as ocean bottom changes, but much smaller. Here we employ the geoid change from NKG2016LU as a trend correction in ocean bottom deformation. The findings contribute valuable insights for predicting sea level changes in the Baltic Sea, emphasizing the significance of accounting for gravitational and volumetric factors along with ocean bottom deformation in sea-level research.

How to cite: Qiu, F., Gruber, T., and Pail, R.: Investigation of sea level variations and trends in the Baltic Sea from geometric and gravimetric observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12665, https://doi.org/10.5194/egusphere-egu24-12665, 2024.

ICGEM is one of the five services coordinated by the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG). The service has been actively responding to the needs of the scientific community for the last two decades with an archive of static, temporal, and topographic global gravity field models of the Earth in a standardized format with the possibility to assign DOIs. Furthermore, ICGEM provides interactive calculation and visualisation services of gravity field functionals. Maintenance of such a service and development of new “demand-based” tools are of utmost importance to provide state-of-the-art products.

In 2016, the ICGEM portal has been renewed to guarantee a smooth transition to future needs. Since then, the last remaining component of the previous ICGEM portal, the G3 Browser, has been upgraded and integrated into the present ICGEM portal. The G3 Browser (http://icgem.gfz-potsdam.de/g3) aims to compute time series of equivalent water height interactively and gives users the opportunity to compare different gravity model time series as well as impacts of corrections (e.g., GIA, C20) or filters. The G3 Browser is complementary to existing services such as GFZ’s GravIS portal which provides ready-to-use products based on GFZ and COST-G solutions with already applied corrections and filters. On the other hand, the ICGEM G3 Browser includes time series from further processing centres and institutions and different filtering options.

Recently, ICGEM has included simulated models (http://icgem.gfz-potsdam.de/sl/simulated) in its archive that are relevant to future gravity mission studies. Currently available simulated Level 2a models are from the ESA’s MAGIC simulation studies and they are the first of their kind on the ICGEM Service. Monthly and weekly series of different scenarios have been made available on the relevant pages together with the links to the publications provided by the authors.

As demanded by the users, ICGEM plans to include some practical tools in the service, such as comparison of the functionals computed based on two different models and interactive evaluation tools n spatial and spectral domains. Finally, a new project called SAMDAT (Service and Archive for Mass Distribution And mass Transport data) that is funded by the German Research Foundation will be realized during the next three years which aims to expand the ICGEM service based on FAIR (Findable, Accessible, Interoperable, Reusable) data and a sustainable data archive principles.

How to cite: Ince, E. S., Reißland, S., Förste, C., and Flechtner, F.: 20 years of the ICGEM Service and the new developments  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8196, https://doi.org/10.5194/egusphere-egu24-8196, 2024.

This paper presents the next step of the recently undertaken comparison of the tropospheric parameters independently derived from the analysis of Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite Systems (GNSS) data. We established a concept of cross-validation of the tropospheric parameters which allows us to focus now on the investigation of the discrepancies detected in the cross-validation. In particular, the dataset and its parameterization are examined in view of their impact on the obtained biases. The most recent 5 years of observations are considered, during which the sufficiently dense time series of observations are available for the legacy VLBI stations as well as for the new generation antennas following the VLBI Global Observing System (VGOS) specifications. In our study the co-location sites are limited to those observatories, where the legacy VLBI antenna, VGOS antenna and GNSS receiver are present. Furthermore, the tropospheric parameters are compared only at the common epochs, which are chosen to include the independently conducted observations of the legacy VLBI antenna, VGOS antenna and GNSS receiver during a defined time span. The corresponding solution parametrization is varied between intervals of VGOS, legacy and GNSS solution parametrizations in order to identify the most optimal duration. While the parameterization of the GNSS solution considers the tropospheric variations stable over 2 hours, the parameterization of VLBI solutions for legacy antennas is known to be reliable over a shorter 1-hour interval. The highly dense VGOS observations allow us to reach up to 20-minute duration without losing performance.

How to cite: Walenta, A., Flohrer, C., Dach, R., Thaller, D., and Engelhardt, G.: Investigating the independently derived tropospheric parameters at GNSS-VLBI co-located sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6267, https://doi.org/10.5194/egusphere-egu24-6267, 2024.

How to cite: Anastasiou, D., Papanikolaou, X., Serelis, G., and Tsakiri, M.: Velocity field estimated from HEPOS permanent GNSS network in Greece, preliminary results., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17390, https://doi.org/10.5194/egusphere-egu24-17390, 2024.

In the complex geodynamic context of the central Mediterranean, squeezed between the two major tectonic plates of Africa and Eurasia, the Adria microplate plays a key role in modulating the deformation and seismicity of the region. The northern sector of Adria is of particular interest as it exhibits moderate seismicity despite low deformation rates.

The crustal deformation is monitored thanks to the various geodetic networks in the area, which can provide continuous and highly accurate daily data. The geodetic network with the most stations is the Friuli Regional Deformation Network - FReDNet (https://frednet.crs.ogs.it), set up by the National Institute of Oceanography and Applied Geophysics – OGS, to monitor the distribution of crustal deformation and provide complementary information for regional seismic hazard assessment (Zuliani et al., 2018). FReDNet currently counts 22 permanent GNSS stations homogeneously covering the Eastern Alps, the alluvial plain, and the coastal areas of northeastern Italy. Most of the time series are longer than 15 years. In addition to FReDNet, another geodetic network in northeastern Italy, the Marussi GNSS network, comprises ten stations and is managed by the Friuli Venezia Giulia (FVG) region. The geodetic network of the Veneto region in the west and the permanent GNSS networks of Austria and Slovenia in the North and East respectively, complete the puzzling northern border of the Adria microplate opposite the southern front of Eurasia.

We processed daily GNSS data from the different permanent geodetic networks using the GAMIT/GLOBK software package version 10.71 (Herring et al., 2018). Data processing was performed on the HPC cluster GALILEO100 of CINECA, which uses the SLURM system for job scheduling and workload management (Tunini et al., 2023).

This study shows the processing results, in the form of time-series and velocity field, as well as the different aspects taken into account to check the reliability of the processing procedure applied and the results obtained, such as the consideration or avoidance of tidal or non-tidal loads or the change of the reference stations, the influence of the type of GNSS monuments, or the location of the geodetic antenna on a roof or in an open field.

OGS and CINECA supported this research under the HPC-TRES program. We acknowledge the CINECA award under the ISCRA initiative for the availability of high performance computing resources and support (IscraC IsC96_GPSIT-2 and IsCa7_GPS-MAST).

References

Herring, T.A. and King, R., Floyd, M.A. and McClusky, S. C.; 2018: GAMIT Reference Manual: GPS Analysis at MIT, Release 10.7. Department of Earth. Tech. rep., Massachusetts Institute of Technology, Cambridge, Mass. URL: <http://geoweb.mit.edu/gg/Intro_GG.pdf>

Tunini, L., Magrin, A., Rossi, G., and Zuliani, D.;  2023: GNSS time series and velocities about a slow convergent margin processed on HPC clusters: products and robustness evaluation, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2023-131, in review.

Zuliani, D., Fabris, P., Rossi, G.; 2018: FReDNet: Evolution of permanent GNSS receiver system. In: New Advanced GNSS and 3D Spatial Techniques Applications to Civil and Environmental Engineering, Geophysics, Architecture, Archeology and Cultural Heritage, Lecture Notes in Geoinformation and Cartography; Cefalo, R., Zielinski, J., Barbarella, M., Eds.; Springer: Cham, Switzerland, pp.123–137.

How to cite: Tunini, L., Magrin, A., Rossi, G., and Zuliani, D.: Crust deformation in the Northern Adria plate from twenty years of geodetic monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19907, https://doi.org/10.5194/egusphere-egu24-19907, 2024.

The accuracy and robustness of the International Terrestrial Reference Frame lies in the combination of the four space-geodetic techniques. Network imbalances, partly caused by geography and land coverage strongly favour the northern hemisphere in the number of observations and, to a less clear extent, in accuracies. This is evident in large tie discrepancies, for example in Katherine and Yarragadee in Australia, where results from the various techniques differ to a significant degree.

In this contribution we investigate the hypothesis that those discrepancies stem from deficiencies in the global combination of the various techniques, rather than from the individual observations. Specifically, we show that a regionally processed VLBI dataset is superior in its local station coordinate repeatabilities than when processed as part of the global network.

The Australian AuScope VLBI network has been operating for over 10 years, delivering higher cadence and partly more precise observations than the regular global IVS observations. It is our aim here to investigate whether a local comparison between VLBI and GNSS data in Australia can shed light into the mystery of significant tie discrepancies that are currently present in the ITRF for this region.

How to cite: McCallum, L.: High-cadence VLBI in Australia for an improved TRF in the southern hemisphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2949, https://doi.org/10.5194/egusphere-egu24-2949, 2024.

Creating an absolute space-tie where all the geodetic methods are onboard is the key for an improved and stable terrestrial reference frame as well as with various scientific applications. Such satellite concepts  have already been proposed to achieve an accurate and stable terrestrial reference frame. Next generation  Galileo satellites can provide a single well-calibrated platform for the colocation of the space-based geodetic techniques establishing precise and stable ties between the key geodetic techniques.  One of the most crucial and novel aspect of such concepts is the VLBI transmitter (VT) which will emit quasar-like signals from the space to be observed by the VLBI ground stations. VT can directly link the terrestrial and celestial reference frames and bring the unique features of VLBI technique to an Earth orbiting satellite. In the context of call for future Galileo payloads a novel VT has been under development.  VT shall be compatible both with the legacy and VGOS antennas.  Here, we present the progress on ongoing ESA study for VT for Galileo as well as for other future  missions. 

How to cite: Karatekin, Ö., Sert, H., Vasseur, H., Dehant, V., Ritter, B., Hugentobler, U., Kodet, J., Jelić, Ž., Paternoster, K., Kronschnabl, G., Ploetz, C., Gunessee, A., Lopez Rosson, G., and Krishnan, A.: VLBI signal transmitter onboard Earth orbiting satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10637, https://doi.org/10.5194/egusphere-egu24-10637, 2024.

GMV is developing FocusPOD, a suite of tools for POD and geodesy, powered by GMV MAORI, a new GMV in-house Flight Dynamics & Geodesy library, written from scratch in modern C++ and python. FocusPOD supports several projects led by GMV, including the operational provision of Precise Orbit Determination (POD) products of the Copernicus Sentinel satellites in the frame of the CPOD Service, the simulation of tracking data for Galileo 2^nd Generation (G2G) System Test Bed, and other space debris and flight dynamics activities.

FocusPOD is currently capable of processing GNSS data, with a focus on on-board receivers to support POD, and Satellite Laser Ranging (SLR), mostly used in CPOD as an external orbit validation source. Capabilities to process DORIS have been recently added, also targeting POD applications as a first step. GMV’s roadmap for FocusPOD include processing VLBI in addition to these 3 techniques, with the target of becoming a reference software for the geodesy community.

This contribution intends to present FocusPOD roadmap to incorporate VLBI processing capabilities, describing the modelling challenges that have been identified and the various steps that will be taken to finally be able to process VLBI and provide VLBI-based ITRF products. As part of this roadmap, other parallel activities to tie together the rest of the techniques will also be undertaken and described, mostly related to the ground-based processing of GNSS, SLR and DORIS data.

How to cite: Fernández, C., Fernández, M., and Fernández, J.: VLBI processing in FocusPOD, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7935, https://doi.org/10.5194/egusphere-egu24-7935, 2024.

We estimated the true Length of Day (LOD) from DORIS observations. The DORIS RINEX data has been processed by the DORIS development version of the Bernese GPS Software 5.2. We performed single satellite and multisatellite (Sentinel-6A, Sentinel-3A, Sentinel-3B, Jason-3, HY-2C, HY-2D, SARAL, and Cryosat-2), and pre-eliminated solutions. The DORIS data has been processed separately for each satellite on the basis of daily arcs. The troposphere, frequency offset, and orbit parameters were pre-eliminated from the normal equation systems and the finalized matrices were combined on a weekly basis. Hence, individual satellite solutions as well as multi-satellite combined solutions were created. From this solution, we calculated the transformation parameters w.r.t. ITRF 2020 (more precisely w.r.t. the DORIS extension DPOD 2020,) and after applying the 7-parameter Helmert transformation we calculated the RMS w.r.t. DPOD 2020.

We performed solutions with different settings, in particular with different handling of cross-track once-per-revolution harmonic parameters (adjusted with different constraints or not adjusted), since the amplitude of the sine term correlates with LOD. For a comparison of our results, we used the IERS 20 C04 model as a reference.

How to cite: Kumar, V., Stepanek, P., Filler, V., Dikshit, O., and Balasubramanian, N.: Estimation of the Length of Day (LOD) from DORIS observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6362, https://doi.org/10.5194/egusphere-egu24-6362, 2024.

For more than 20 years, Japan Coast Guard has been developing various technologies to improve the observation accuracy of GNSS-Acoustic ranging. In this presentation, I will introduce two topics that we have been paying attention to in recent years in GNSS-A observations.

The first is about instrument errors and angular characteristics that depend on the shape of the transducer (sea surface station) or transponder (seafloor station). In the long-term observations conducted by JCG, multiple types of oscillators are used on both transducers and transponders. It has become clear that this instrumental error has a non-negligible effect on the positioning accuracy of GNSS-A, so we develop a new method to read a received signal considering the instrumental and angle dependence.

The second is about a representation method of ocean structure. When we estimate positioning of seafloor station, it is very important to consider sound speed structure (SSS). We use the open-source software GARPOS which can estimate transponder position with SSS. Yokota et al., (in prep) introduce a new representation method of SSS with G-ellipse in GNSS-A analysis. I will talk about the meaning of G-ellipse and some applications of this method.

How to cite: Nagae, K., Ishikawa, T., Watanabe, S., Nakamura, Y., and Yokota, Y.: Device and angle dependent waveform and a new representation of ocean sound speed structure in GNSS-A, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13228, https://doi.org/10.5194/egusphere-egu24-13228, 2024.

The Japanese Archipelago lies along subduction zones, where megathrust earthquakes are known to occur repeatedly (e.g., M_w 9.0 2011 Tohoku-oki Earthquake). The source regions of such megathrust earthquakes mainly lie beneath the seafloor, making it necessary to monitor the crustal deformation not only on land but also on the seafloor. The Japan Coast Guard (JCG) has been conducting seafloor geodetic observation using the GNSS-Acoustic ranging combination technique (GNSS-A) since the early 2000s. By combining GNSS and underwater acoustic ranging, GNSS-A measures the absolute position of a seafloor benchmark in the precision of centimeters, which provides us fruitful information on the crustal deformation under ocean. JCG currently deploys 27 seafloor sites along the Japan Trench and the Nankai Trough named the Seafloor Geodetic Observation Array (SGO-A).

JCG and the Univ. Tokyo group has been working on open data of GNSS-A. In the past, we have published the position time series data (Yokota et al. 2018), and the GARPOS software (Watanabe et al. 2020) which is used in our current routine analysis. Recently, we have been discussing on a standardized data format for GNSS-A in the task force of the Inter-Commission Committee on Marine Geodesy (ICCM) in the International Association of Geodesy. Currently, we are releasing the latest position time series data of each SGO-A site, and the GNSS-A observation dataset in the GARPOS data format (https://www1.kaiho.mlit.go.jp/chikaku/kaitei/sgs/datalist_e.html).

How to cite: Nakamura, Y., Ishikawa, T., Watanabe, S., Nagae, K., and Yokota, Y.: Overview of Japan Coast Guard’s GNSS-A seafloor geodetic observation and data management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15420, https://doi.org/10.5194/egusphere-egu24-15420, 2024.