The Global Geodetic Observing System (GGOS) provides measurements of the time varying gravity, rotation, and shape of the Earth using geodetic and gravimetric instruments located on the ground and in space. These measurements need to be accurate to better than a part per billion in order to advance our understanding of the underlying processes that are causing the Earth's rotation, gravity, and shape to change. Mass transport in the global water cycle, sea level and climate change, and crustal deformation associated with geohazards are examples of particularly demanding applications of geodetic and gravimetric measurements. All these measurements require a common reference with the same precision, like the Terrestrial Reference Frame and the Unified Height System. GGOS is designed to unite the individual observations and model into one consistent frame with the highest precision available. This session should be a platform for discussing improvements to global geodetic observing systems including multidisciplinary approaches as well as for single contributions with high precision in a global network.

Convener: Kosuke Heki | Co-conveners: Detlef Angermann, Richard Gross, Michael R. Pearlman
| Attendance Tue, 05 May, 08:30–10:15 (CEST)

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Chat time: Tuesday, 5 May 2020, 08:30–10:15

D1735 |
Jerome Saunier, Guilhem Moreaux, and Frank G. Lemoine

The Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) system is based on a homogeneous global geodetic network. The DORIS ground network is managed and monitored by a single entity (CNES/IGN), which makes it possible to closely steer its deployment and evolution. Moreover, thanks to infrastructure and hardware improvements, the DORIS network has continuously improved over time in order to meet the performance requirements of satellite altimetry for which it is mainly dedicated.

Today, the numerous strengths of the DORIS network built up over 30 years give it an important role in contributing to the Global Geodetic Observing System (GGOS). Our extensive experience in geodetic network maintenance and long-standing commitment to international cooperation to co-locate DORIS with other space geodetic techniques and tide gauges led us to define installation requirements at co-located sites and monuments installation specifications.

After presenting an overview of the DORIS system specificities, we review the strengths and assets of the DORIS network and the continuing improvements in the DORIS technique. Then, we present examples of concrete results achieved through improved ground station configurations. Finally, we give an update on the status and plans for the DORIS network in the coming years to overcome the current limitations of DORIS to meet the GGOS goals for the Terrestrial Reference Frame.

How to cite: Saunier, J., Moreaux, G., and Lemoine, F. G.: DORIS infrastructure: status and plans after 30 years of service, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3558, https://doi.org/10.5194/egusphere-egu2020-3558, 2020.

D1736 |
Dirk Behrend, Axel Nothnagel, Johannes Böhm, Chet Ruszczyk, and Pedro Elosegui

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. The VLBI activities are associated with the creation, provision, dissemination, and archiving of relevant VLBI data and products. The operational station network of the IVS currently consists of about 40 radio telescopes worldwide, subsets of which participate in regular 24-hour and 1-hour observing sessions. This legacy S/X observing network dates back in large part to the 1970s and 1980s. Because of highly demanding new scientific requirements such as sea-level change but also due to the aging infrastructure, the larger IVS community planned and started to implement a new VLBI system called VGOS (VLBI Global Observing System) at existing and new sites over the past several years. In 2020, a fledgling network of 8 VGOS stations started to observe in operational IVS sessions. We anticipate that the VGOS network will grow over the next couple of years to a global network of 25 stations and will eventually replace the legacy S/X system as the IVS production system. We will provide an overview of the recent developments and anticipated evolution of the geodetic VLBI station infrastructure.

How to cite: Behrend, D., Nothnagel, A., Böhm, J., Ruszczyk, C., and Elosegui, P.: Station Infrastructure Developments of the IVS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12847, https://doi.org/10.5194/egusphere-egu2020-12847, 2020.

D1737 |
Ryan Ruddick, Amy Peterson, Richard Jacka, and Bart Thomas

Having modern and well-maintained geodetic infrastructure is critical for the development of an accurate and reliable Global Geodetic Reference Frame (GGRF). Geoscience Australia (GA) contributes to the development of the GGRF through a network of Global Navigation Satellite System (GNSS) reference stations positioned in key locations across Australia, Antarctica and the Pacific. Data from these reference stations contribute to the realisation of the GGRF, the development and maintenance of the Asia-Pacific Reference frame and the monitoring of deformation across the Australian continent. We are also seeing a rapid increase in the use of this data for location-based positioning applications, such as civil engineering, transport, agriculture and community safety. These applications bring with them a new suite of challenges for geodetic infrastructure operators, such as reduced data latency, denser networks and accessing the latest signals in the most modern formats. Through the Positioning Australia program, GA is addressing these challenges by developing a modern highly-available GNSS reference station design that will be deployed at over 200 sites across the region. This paper discusses the concept of highly-available infrastructure and presents a GNSS reference station design that is openly available for use by the global geodetic community.

How to cite: Ruddick, R., Peterson, A., Jacka, R., and Thomas, B.: Developing a highly-available GNSS reference station network, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12593, https://doi.org/10.5194/egusphere-egu2020-12593, 2020.

D1738 |
Riccardo Barzaghi, Laura Sanchez, and George Vergos

An objective of the International Height Reference System (IHRS) and its realization (the IHRF) is to support the monitoring and analysis of Earth’s system changes. The more accurate the IHRS/IHRF is, the more phenomena can be identified and modelled. Thus, the IHRS/IHRF must provide vertical coordinates and their changes with time as accurately as possible. As many global change phenomena occur at different scales, the global frame should be extended to regional and local levels to guarantee consistency in the observation, detection, and modelling of their effects. From this perspective, an operational infrastructure is needed to ensure the long-term sustainability of the IHRS/IHRF. In this contribution, we discuss the possibility of establishing such as infrastructure within the International Association of Geodesy (IAG) and its International Gravity Field Service (IGFS). Some aspects to be considered are:

  • - Improvements in the IHRS definition and realization following future developments in geodetic theory, observations and modelling.
  • - Refinement of the IHRS/IHRF standards/conventions based on the unification of the standards/conventions used by the geometric and gravity IAG Services.
  • - Development of strategies for collocation of IHRF stations with existing gravity and geometrical reference stations at different densification levels.
  • - Identification of the geodetic products associated with the IHRF and description of the elements to be considered in the corresponding metadata.
  • - Servicing the vertical datum needs of other geosciences such as, e.g., hydrography and oceanography.
  • - Implementation of a registry containing the existing local/regional height systems and their connections to the global IHRS/IHRF.

How to cite: Barzaghi, R., Sanchez, L., and Vergos, G.: Operational infrastructure to ensure the long-term sustainability of the IHRS/IHRF, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7961, https://doi.org/10.5194/egusphere-egu2020-7961, 2020.

D1739 |
Ulrich Meyer, Adrian Jäggi, Frank Flechtner, Christoph Dahle, Torsten Mayer-Gürr, Andreas Kvas, Jean-Michel Lemoine, Stéphane Bourgogne, Andreas Groh, Annette Eicker, and Benoit Meyssignac

With the release of the combined GRACE monthly gravity field time-series COST-G RL01 the Combination Service for Time-variable Gravity fields (COST-G) of the International Association of Geodesy (IAG) became operational in July 2019. We present the COST-G RL01 time-series and provide validation in terms of orbit fit, ice mass trends, lake altimetry and sea level budget. We identify weak points in the combined monthly gravity fields and discuss possible improvements of the combination strategy for future combinations.

While COST-G RL01 is based on sets of re-processed GRACE monthly gravity fields, COST-G also provides combinations of monthly Swarm high-low satellite-to-satellite tracking (hl-SST) gravity fields on an operational basis with a latency of 3 months. Combinations of GRACE-FO monthly gravity fields are in the process of operationalization. We provide a status report and first results of GRACE-FO combinations. Combined GRACE, Swarm and GRACE-FO gravity fields complement each other to provide a long-term time-series of mass variation in the system Earth.

How to cite: Meyer, U., Jäggi, A., Flechtner, F., Dahle, C., Mayer-Gürr, T., Kvas, A., Lemoine, J.-M., Bourgogne, S., Groh, A., Eicker, A., and Meyssignac, B.: Combination Service for Time-variable Gravity Fields (COST-G) – operations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10380, https://doi.org/10.5194/egusphere-egu2020-10380, 2020.

D1740 |
Karl Ulrich Schreiber, Jan Kodet, Thomas Klügel, and Torben Schüler

The toolbox of space geodesy contains a number of measurement techniques, which are globally distributed. In this diverse network fundamental stations are playing an important role as they are forming the backbone of the global geodetic observing system. They provide the ties for the combination of the techniques.

Until recently these ties were only considering the spatial relationship between the measurement techniques. Upon closer inspection it turns out that clocks are also playing an important role. Variable delays within the main techniques of space geodesy, namely SLR, VLBI, GNSS and DORIS are limiting the stability of the measurements and hence the entire observing system. This leads to the rather paradox situation, that each technique has to adjust the clock offsets independently. Although all main measurements systems on an observatory are usually based on the same clock, each technique provides different offsets, thus weakening the local ties. This reflects the fact that the clock adjustments are also contaminated with (variable) system specific delays. Increasing the coherence of time on these GGOS observatories disentangles erroneous system delays from local ties, thus strengthening the entire observing system. 

We have designed and built such a coherent time and frequency distribution system for the Geodetic Observatory Wettzell. It is based on a mode-locked fs- pulse laser, fed into a network of actively delay controlled two-way optical pulse transmission links. This utilizes the ultra low noise properties of optical frequency combs, both in the optical and electronic regime. Together with a common central inter- and intra- technique reference target time can provide consistency for the complex instrumentation of SLR and VLBI systems in situ, which was not possible before. This talk outlines the concept and its potential for GGOS.

How to cite: Schreiber, K. U., Kodet, J., Klügel, T., and Schüler, T.: Coherent Time and Frequency for an Improved Global Geodetic Observing System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16586, https://doi.org/10.5194/egusphere-egu2020-16586, 2020.

D1741 |
Xiaoya Wang, Zhongping Zhang, Fengchun Shu, Guangli Wang, and Kewei Xi

Chinese space geodetic networks were established in 1990s. The first SLR station in china was setup by Shanghai Astronomical Observatory (SHAO) in 1975 and now there are 7 SLR stations on operation in china. The observation accuracy has been improved from 1m to 8mm and the observation range has been extended from 1000km to 3600km for artificial satellites, 385000km for Lunar Range. The orbit determination accuracy has also been enhanced from several hectometer to 1-2 cm. And the products of SLR Terrestrial Reference Frame (TRF) and EOP is similar with that of other ILRS ACs and CCs. Currently 4 VLBI stations, including Seshan25, Kunming, Urumqi and Tianma65, participate in the IVS observing program. The total number of observing days was increased significantly in the past years. Shanghai VLBI correlator has been operational for the IVS data correlation since 2015. In addition to regular geodesy, we are also actively involved in the UT1 measurements and densification of the ICRF. We obtained first fringes between the two VGOS antennas at Shanghai in July 2019. A few more VGOS antennas will be built by collaborating with our partners in China or abroad. SHAO has provided the VLBI products such as POS+EOP to IVS. The first GPS station in China was setup in 1992 by JPL under the agreement between CAS and NASA, and now there are over 2000 GNSS stations running by CAS, China Earthquake Administration, Chinese Academy of Surveying & Mapping, China Meteorological Administration, Ministry of Education of the people’s Republic of China, Company and their subdivisions. From the ownership of Chinese GNSS network, we could see the comprehensive applications such as regional TRF densification, EOP measurement, meteorological service, earthquake displacement, ionospheric modelling, crustal movement monitoring, PNT and so on. The first DORIS station was set up in Wuhan in 2003 and now there are 2 DORIS sites in China. Chinese space geodetic networks and their application will be further developed in future.

How to cite: Wang, X., Zhang, Z., Shu, F., Wang, G., and Xi, K.: Status on Chinese Space Geodesy Networks and their Applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4324, https://doi.org/10.5194/egusphere-egu2020-4324, 2020.

D1742 |
Basara Miyahara

The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) provides the basis on which future advances in geosciences can be built. By considering the Earth system as a whole (including the geosphere, hydrosphere, cryosphere, atmosphere and biosphere), monitoring Earth system components and their interactions by geodetic techniques and studying them from the geodetic point of view, the geodetic community provides the global geosciences community with a powerful tool consisting mainly of high-quality services, standards and references, and theoretical and observational innovations. The mission of GGOS is: (a) to provide the observations needed to monitor, map and understand changes in the Earth’s shape, rotation and mass distribution; (b) to provide the global frame of reference that is the fundamental backbone for measuring and consistently interpreting key global change processes and for many other scientific and societal applications; and (c) to benefit science and society by providing the foundation upon which advances in Earth and planetary system science and applications are built. The goals of GGOS are: (1) to be the primary source for all global geodetic information and expertise serving society and Earth system science; (2) to actively promote, sustain, improve, and evolve the integrated global geodetic infrastructure needed to meet Earth science and societal requirements; (3) to coordinate with the international geodetic services that are the main source of key parameters and products needed to realize a stable global frame of reference and to observe and study changes in the dynamic Earth system; (4) to communicate and advocate the benefits of GGOS to user communities, policy makers, funding organizations, and society. In order to accomplish its mission and goals, GGOS depends on the IAG Services, Commissions, and Inter-Commission Committees. The Services provide the infrastructure and products on which all contributions of GGOS are based. The IAG Commissions and Inter-Commission Committees provide expertise and support for the scientific development within GGOS. In summary, GGOS is IAG’s central interface to the scientific community and to society in general. The whole figure of GGOS and its recent focus will be presented in the presentation.

How to cite: Miyahara, B.: Global Geodetic Observing System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13390, https://doi.org/10.5194/egusphere-egu2020-13390, 2020.

D1743 |
Martin Sehnal, Allison Craddock, and Kirsten Elger

The International Association of Geodesy’s (IAG) Global Geodetic Observing System (GGOS) is managed administratively by the GGOS Coordinating Office, based at the Austrian Federal Office of Metrology and Surveying (BEV). The director of GGOS Coordinating Office (CO) supports the Executive Committee, the Coordinating Board and the Science Panel as well as he ensures coordination of the activities of the various GGOS components like the Bureau of Products and Standards (BPS), the Bureau of Networks and Observations (BNO) and the three GGOS Focus Areas.

The Coordinating Office ensures information flow, maintains documentation of GGOS activities, and manages specific assistance functions that enhance the coordination across all areas of GGOS, including coordination among IAG Services and support for workshops. The Coordinating Office, in its long‐term coordination role, ensures that the GGOS components contribute to GGOS and its stakeholder community in a consistent and continuous manner. The Coordinating Office also maintains, manages, and coordinates the GGOS web- and social media presence as well as outreach and external engagement. In 2020 the current GGOS website (www.ggos.org) will be refreshed and redesigned to optimize usability and ease of navigation. The website will serve as a source of information about GGOS, geodetic data, products, and services, as well as other non-technical resources for the IAG community.

On behalf of the GGOS community, the Coordinating Office manages external relations and engagement with stakeholder organizations such as the Group on Earth Observations (GEO), the Committee on Earth Observation Satellites (CEOS) and the International Science Council (ISC) World Data System (WDS). In this capacity, the Office also identifies opportunities to link geodesy with relevant United Nations frameworks and other instruments of engagement, such as the Sendai Framework for Disaster Risk Reduction and the UN-GGIM-World Bank Integrated Geospatial Information Framework.

The Coordinating Office also works to identify opportunities for improved coordination and advocacy within the geodetic community, establishing the Working Group on “Digital Object Identifiers (DOIs) for Geodetic Data Sets” in 2019. This working group consists of more than 20 members affiliated with IAG Services, working to establish usage parameters and advocate for the consistent implementation of DOIs across all IAG Services and in the greater geodetic community.

How to cite: Sehnal, M., Craddock, A., and Elger, K.: GGOS Coordinating Office – Recent Achievements and Activities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6540, https://doi.org/10.5194/egusphere-egu2020-6540, 2020.

D1744 |
Detlef Angermann, Thomas Gruber, Michael Gerstl, Urs Hugentobler, Laura Sanchez, Robert Heinkelmann, and Peter Steigenberger

The Bureau of Products and Standards (BPS) supports GGOS in its goal to obtain consistent products describing the geometry, rotation and gravity field of the Earth. A key objective of the BPS is to keep track of adopted geodetic standards and conventions across all IAG components as a fundamental basis for the generation of consistent geometric and gravimetric products. This poster gives an overview about the organizational structure, the objectives and activities of the BPS. In its present structure, the two Committees “Earth System Modeling” and “Essential Geodetic Variables” as well as the newly established Working Group “Towards a consistent set of parameters for the definition of a new GRS” are associated to the BPS. Recently the updated 2nd version of the BPS inventory on standards and conventions used for the generation of IAG products has been compiled. Other activities of the Bureau include the integration of geometric and gravimetric observations towards the development of integrated products (e.g., GGRF, IHRF, atmosphere products) in cooperation with the IAG Services and the GGOS Focus Areas, the contribution to the re-writing of the IERS Conventions as Chapter Expert for Chapter 1 “General definitions and numerical standards”, the interaction with external stakeholders regarding standards and conventions (e.g., ISO, IAU, BIPM, CODATA) as well as contributions to the Working Group “Data Sharing and Development of Geodetic Standards” within the UN GGIM Subcommittee on Geodesy.

How to cite: Angermann, D., Gruber, T., Gerstl, M., Hugentobler, U., Sanchez, L., Heinkelmann, R., and Steigenberger, P.: The GGOS Bureau of Products and Standards, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7930, https://doi.org/10.5194/egusphere-egu2020-7930, 2020.

D1745 |
Carey Noll, Michael Pearlman, Dirk Behrend, Allison Craddock, Erricos Pavlis, Jérôme Saunier, Elizabeth Bradshaw, Riccardo Barzaghi, Daniela Thaller, Benjamin Maennel, Ryan Hippenstiel, Roland Pail, and Nicholas Brown

The GGOS Bureau of Networks and Observations works with the IAG Services (IVS, ILRS, IGS, IDS, IGFS, and PSMSL) to advocate for the expansion and upgrade of space geodesy networks for the maintenance and improvement of the reference frame and other applications, as well as for the integration with other techniques, including absolute gravity and sea level measurements from tide gauges. New sites are being established following the GGOS concept of “core” and co-location sites, and new technologies are being implemented to enhance performance in data yield as well as accuracy. The Bureau continues to meet with organizations to discuss possibilities, including partnerships, for new and expanded participation. The GGOS Network continues to grow as new stations join every year.

The Bureau holds meetings frequently, providing the opportunity for representatives from the services to meet and share progress and plans, and to discuss issues of common interest. It also monitors the status and projects the evolution of the network based on information from the current and expected future participants. Of particular interest at the moment is the integration of gravity and tide gauge networks and the forthcoming establishment of the new absolute gravity reference frame. 

The IAG Committees and Joint Working Groups play an essential role in the Bureau activity. The Standing Committee on Performance Simulations and Architectural Trade-offs (PLATO) uses simulation and analysis techniques to project future network capability and to examine trade-off options. The Committee on Data and Information is working on a strategy for a GGOS metadata system for data products and a more comprehensive long-term plan for an all-inclusive system. The Committee on Satellite Missions is working to enhance communication with the space missions, to advocate for missions that support GGOS goals and to enhance ground systems support. The IERS Working Group on Site Survey and Co-location (also participating in the Bureau) is working to enhance standardization in procedures, outreach and to encourage new survey groups to participate and improve procedures to determine systems’ reference points, a crucial aid in the detection of technique-specific systematic errors.
We will give a brief update on the status and projection of the network infrastructure of the next several years, and the progress and plans of the Committees/Working Group in their critical role in enhancing data product quality and accessibility to the users.   

How to cite: Noll, C., Pearlman, M., Behrend, D., Craddock, A., Pavlis, E., Saunier, J., Bradshaw, E., Barzaghi, R., Thaller, D., Maennel, B., Hippenstiel, R., Pail, R., and Brown, N.: GGOS Bureau of Networks and Observations: Network Infrastructure and Related Activities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22473, https://doi.org/10.5194/egusphere-egu2020-22473, 2020.

D1746 |
Michael R. Pearlman, Carey Noll, Erricos Pavlis, Toshimichi Otsubo, Jean-Marie Torre, Ulrich Schreiber, Georg Kirchner, and Michael Steindorfer Steindorfer

The International Laser Ranging Service (ILRS) is improving its services through network expansion and continuous upgrades of its modeling and analysis approaches. New ground stations are being deployed with higher repetition rate systems, more efficient detection, and increased automation; new technologies are also being adopted at some of its legacy stations. In addition, the roster of tracking missions is rapidly expanding. The top priority for the Service continues to be its contribution to the reference frame development, but of increasing importance is also the tracking of GNSS satellites, including the anticipated deployment of the new GPS III constellation over this decade. These requirements are being reflected in new system designs and updates. Stations are also being adapted to accommodate ground and space-time synchronization. A few stations continue with their lunar laser ranging activities while several others have begun testing their ability to do lunar ranging in the future. About a dozen stations are active in space-debris tracking for studies of orbital dynamics and reentry predictions. New tools and procedures have been implemented to improve the quality of SLR data and derived products, and to expedite the resolution of engineering issues. Work also continues on the design and building of improved retroreflector targets to maximize data quality and quantity.

 This paper will give an overview of activities underway within the Service, paths forward and presently envisioned, and current issues and challenges.

How to cite: Pearlman, M. R., Noll, C., Pavlis, E., Otsubo, T., Torre, J.-M., Schreiber, U., Kirchner, G., and Steindorfer, M. S.: Recent Progress and Plans for Improvement of ILRS Infrastructure and Data Product Delivery, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5613, https://doi.org/10.5194/egusphere-egu2020-5613, 2020.

D1747 |
Richard Gross

The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) provides the basis on which future advances in geosciences can be built. By considering the Earth system as a whole (including the geosphere, hydrosphere, cryosphere, atmosphere and biosphere), monitoring Earth system components and their interactions by geodetic techniques and studying them from the geodetic point of view, the geodetic community provides the global geosciences community with a powerful tool consisting mainly of high-quality services, standards and references, and theoretical and observational innovations. A new initiative within GGOS is to define Essential Geodetic Variables. Essential Geodetic Variables (EGVs) are observed variables that are crucial (essential) to characterizing the geodetic properties of the Earth and that are key to sustainable geodetic observations. Once a list of EGVs has been determined, requirements can be assigned to them such as the accuracy with which the variables need to be determined, their spatial and temporal resolution, latency, etc. These requirements on the EGVs can then be used to assign requirements to EGV-dependent products like the terrestrial reference frame. The EGV requirements can also be used to derive requirements on the systems that are used to observe the EGVs, helping to lead to a more sustainable geodetic observing system for reference frame determination and numerous other scientific and societal applications.

For the Earth's rotation, the essential variables can be considered to be the five Earth orientation parameters (EOPs), namely, the x- and y-components of polar motion (xp, yp), the x- and y-components of nutation/precession (X, Y), and the spin parameter UT1. Related to these five Essential Earth Rotation Variables are the sub-variables of their time rates-of-change and the derived variables of the excitation functions (χx, χy, and length-of-day). The Essential Earth Rotation Variables are currently observed by the operational techniques of lunar and satellite laser ranging, very long baseline interferometry, global navigation satellite systems, and Doppler orbitography and radiopositioning integrated by satellite. In the future, the emerging techniques of ring laser gyroscopes and superfluid helium gyroscopes can be expected to routinely observe parameters related to the Essential Earth Rotation Variables. The GGOS requirements on the five Essential Earth Rotation Variables (that is, on the five EOPs) are "ERP-001-EOP: Earth Orientation Parameters will be determined with an accuracy of 1 mm, a temporal resolution of 1 hour, and a latency of 1 week; near real-time determinations of the Earth Orientation Parameters will be determined with an accuracy of 3 mm" (Plag and Pearlman, 2009, p. 223). Currently, the best-determined EOPs have an accuracy of about 1 mm, a temporal resolution of about 1 day, and a latency of about 2 weeks (Ray et al., 2017; http://www.igs.org/products). Thus, while the GGOS accuracy requirement on the Essential Earth Rotation Variables is currently being met, at least for some of the variables, the GGOS resolution and latency requirements are not being met.

How to cite: Gross, R.: Essential Geodetic Variables: Earth Orientation Parameters, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2434, https://doi.org/10.5194/egusphere-egu2020-2434, 2020.

D1748 |
Kirsten Elger, Glenda Coetzer, and Roelf Botha and the GGOS DOI Working Group

Only four years after the implementation of digital object identifiers (DOIs) for unambiguously identifying and linking to online articles, the first DOI for digital datasets was registered in 2004. Originally developed with the purpose of providing permanent access to (static) datasets described in scholarly literature (to allow reproducibility and scrutiny of research results), DOIs today are increasingly used for dynamic datasets (e.g. time series from observational networks, where new data values are added frequently given that the originally published data will not change), collections or networks. These DOIs (and other persistent identifiers) are mainly assigned for providing a citable and traceable reference to various types of sources (data, software, samples, equipment) and means of rewarding the originators and institutions.

As a result of international groups, like the Coalition for Publishing Data in the Earth and Space Sciences (COPDESS) and the Enabling FAIR Data project, datasets with assigned DOIs are now fully citable in scholarly literature - many journals require the data underlying a publication to be available before accepting an article. Initial metrics for data citation are available and allow data providers to demonstrate the value of the data collected by institutes and individual scientists – which makes them even more attractive.

This is especially relevant in the framework of evaluation criteria for institutions and researchers, that usually only consider scientific output in the form of scholarly literature and citation numbers. Compared to other scientific disciplines, geodesy researchers appear to be producing less “countable scientific” output. Geodesy researchers, however, are much more involved in operational aspects and data provision than researchers in other fields might be. Geodesy data and equipment therefore require a structured and well-documented mechanism which will enable citability, scientific recognition and reward that can be provided by assigning DOI to data, data products and scientific software.

To address these challenges and to identify opportunities for improved coordination and advocacy within the geodetic community, the International Association of Geodesy’s (IAG) Global Geodetic Observing System (GGOS) has established a Working Group on “Digital Object Identifiers (DOIs) for Geodetic Data Sets”. The GGOS DOI Working Group (with more than 20 members) officially started with a first meeting during December 2019, co-located to the AGU Fall Meeting. Beginning with an assessment of DOI minting strategies that are already implemented, the GGOS DOI Working Group is designated to establish best practices and advocate for the consistent implementation of DOIs across all IAG Services and in the greater geodetic community.

How to cite: Elger, K., Coetzer, G., and Botha, R. and the GGOS DOI Working Group: Why do Geodetic Data need DOIs? First ideas of the GGOS DOI Working Group, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17861, https://doi.org/10.5194/egusphere-egu2020-17861, 2020.

D1749 |
Toshimichi Otsubo, Basara Miyahara, Yusuke Yokota, Shinobu Kurihara, Hiroshi Munekane, Shun-ichi Watanabe, Takayuki Miyazaki, Hiroshi Takiguchi, Yuichi Aoyama, Koichiro Doi, Yoichi Fukuda, Koji Matsuo, Takaaki Jike, Takehiro Matsumoto, and Ryuichi Ichikawa

Since the establishment in 2013, GGOS Japan, formerly known as GGOS Working Group of Japan, has actively contributed to domestic and international space-geodetic activities.  Until it was established, six Japanese agencies with their own backgrounds and missions had individually conducted geodetic observations of GNSS, VLBI, SLR, DORIS and gravimetry in Japan and Antarctica.   GGOS Japan was established to strengthen the collaboration between the agencies and to get connected to international organizations such as IAG and GGOS.

Its core members consist of a chair, a secretary, a lead of the outreach working group, a lead of the DOI working group and representatives of five core techniques.  It is supported by tens of people in Japan and also by its parent entity, IAG subcommittee in Japan.

This presentation will cover our achievement such as assembling our site list, hosting various domestic/international meetings, planning a special issue in a domestic journal, producing its leaflet and website and so on.  Since 2017 it has been approved as an GGOS Affiliate and it is remarkable that Basara Miyahara was elected as GGOS President in 2019.

How to cite: Otsubo, T., Miyahara, B., Yokota, Y., Kurihara, S., Munekane, H., Watanabe, S., Miyazaki, T., Takiguchi, H., Aoyama, Y., Doi, K., Fukuda, Y., Matsuo, K., Jike, T., Matsumoto, T., and Ichikawa, R.: GGOS Japan: Uniting Space Geodetic Activities in Japan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3244, https://doi.org/10.5194/egusphere-egu2020-3244, 2020.

D1750 |
Michael Schmidt and Ehsan Forootan

Space weather means a very up-to-date and interdisciplinary field of research. It describes physical processes in space mainly caused by the Sun’s radiation of energy. The manifestations of space weather are multiple, for instance, the variations of the Earth’s magnetic field or the changing states of the upper atmosphere, in particular the ionosphere and the thermosphere.

The main objectives of the Focus Area on Geodetic Space Weather Research (FA GSWR) are (1) the development of improved ionosphere models, (2) the development of improved thermosphere models and (3) the study of the coupled processes between magnetosphere, ionosphere and thermosphere (MIT). 

Objective (1) aims at the high-precision and the high-resolution (spatial and temporal) modelling of the electron density. This allows to compute a signal propagation delay, which will be used in many geodetic applications, in particular in positioning, navigation and timing (PNT). Moreover, it is also important for other techniques using electromagnetic waves, such as satellite- or radio-communications. Concerning objective (2), satellite geodesy will obviously benefit when working on Precise Orbit Determination (POD), but there are further technical matters like collision analysis or re-entry calculation, which will become more reliable when using high-precision and high-resolution thermospheric drag models. Objective (3) links the magnetosphere with the first two objectives by introducing physical laws and principles such as continuity, energy and momentum equations and solving partial differential equations.     

To arrive at the above described objectives of the FA GSWR one new Joint Study Groups (JSG) and three Joint Working Groups (JWG) have been installed recently. In detail, these groups are titled as JSG 1: Coupling processes between magnetosphere, thermosphere and ionosphere, JWG 1: Electron density modelling, JWG 2: Improvement of thermosphere models, and JWG 3: Improved understanding of space weather events and their monitoring by satellite missions. Other implemented IAG Study and Working Groups within the IAG programme 2019 to 2023 will provide valuable input for the FA GSWR. In this presentation we provide the latest investigations and results from the above mentioned Joint Study and Working Groups JSG 1, JWG 1, JWG 2 and JWG 3 of the FA GSWR.

How to cite: Schmidt, M. and Forootan, E.: GGOS Focus Area on Geodetic Space Weather Research – Current Status, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20304, https://doi.org/10.5194/egusphere-egu2020-20304, 2020.

D1751 |
Laura Sanchez and Riccardo Barzaghi

The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG), providing precise geodetic infrastructure and expertise for monitoring the System Earth, promotes the standardization of height systems worldwide. The GGOS Focus Area "Unified Height System” (GGOS-FA-UHS, formerly Theme 1) was established at the 2010 GGOS Planning Meeting (February 1 - 3, Miami, Florida, USA) to lead and coordinate these efforts. Starting point was the results delivered by the IAG Inter-Commission Project 1.2 "Vertical Reference Frames" (IAG ICP1.2 VRF), which was operative from 2003 to 2011. During the 2011-2015 term, different discussions focussed on the best possible definition of a global unified vertical reference system resulted in the  IAG resolution for the "Definition and realization of an International Height Reference System (IHRS)” that was approved during the 2015 General Assembly of the International Union of Geodesy and Geophysics (IUGG) in Prague, Czech Republic. The immediate objectives of the GGOS-FA-UHS are (1) to outline detailed standards, conventions, and guidelines to make the IAG Resolution applicable, and (2) to establish the realization of the IHRS, i.e., the International Height Reference Frame (IHRF). This contribution summarizes the main achievements of the GGOS-FA-UHS and provides a review of the open questions that need to be resolved in the near future.

How to cite: Sanchez, L. and Barzaghi, R.: Activities and plans of the GGOS Focus Area Unified Height System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8625, https://doi.org/10.5194/egusphere-egu2020-8625, 2020.

D1752 |
Elizabeth Bradshaw, Andy Matthews, Kathy Gordon, Angela Hibbert, Sveta Jevrejeva, Lesley Rickards, Simon Williams, and Philip Woodworth

The Permanent Service for Mean Sea Level (PSMSL) is the global databank for long-term mean sea level data and is a member of the Global Geodetic Observing System (GGOS) Bureau of Networks and Observations. As well as curating long-term sea level change information from tide gauges, PSMSL is also involved in developing other products and services including the automatic quality control of near real-time sea level data, distributing Global Navigation Satellite System (GNSS) sea level data and advising on sea level metadata development.
At the GGOS Days meeting in November 2019, the GGOS Focus Area 3 on Sea Level Change, Variability and Forecasting was wrapped up, but there is still a requirement in 2020 for GGOS to integrate and support tide gauges and we will discuss how we will interact in the future. A recent paper (Ponte et al., 2019) identified that only “29% of the GLOSS [Global Sea Level Observing System] GNSS-co-located tide gauges have a geodetic tie available at SONEL [Système d'Observation du Niveau des Eaux Littorales]” and we as a community still need to improve the ties between the GNSS sensor and tide gauges. This may progress as new GNSS Interferometric Reflectometry (GNSS-IR) sensors are installed to provide an alternative method to observe sea level. As well as recording the sea level, these sensors will also provide vertical land movement information from one location. PSMSL are currently developing an online portal of uplift/subsidence land data and GNSS-IR sea level observation data. To distribute the data, we are creating/populating controlled vocabularies and generating discovery metadata.
We are working towards FAIR data management principles (data are findable, accessible, interoperable and reusable) which will improve the flow of quality controlled sea level data and in 2020 we will issue the PSMSL dataset with a Digital Object Identifier. We have been working on improving our discovery and descriptive metadata including creating a use case for the Research Data Alliance Persistent (RDA) Identification of Instruments Working Group to help improve the description of a time series where the sensor and platform may change and move many times. Representatives from PSMSL will sit on the GGOS DOIs for Data Working Group and would like to contribute help with controlled vocabularies, identifying metadata standards etc. We will also contribute to the next GGOS implementation plan.
Ponte, Rui M., et al. (2019) "Towards comprehensive observing and modeling systems for monitoring and predicting regional to coastal sea level." Frontiers in Marine Science 6(437).

How to cite: Bradshaw, E., Matthews, A., Gordon, K., Hibbert, A., Jevrejeva, S., Rickards, L., Williams, S., and Woodworth, P.: Sea level in the Global Geodetic Observing System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3054, https://doi.org/10.5194/egusphere-egu2020-3054, 2020.

D1753 |
Thomas Gruber, Jonas Ågren, Detlef Angermann, Artu Ellmann, Christoph Gisinger, Jolanta Nastula, Xanthi Oikonomidou, and Markku Poutanen

Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national levelling networks and therefore define a height system of a country. Thus, sea level research across countries is closely linked to height system unification and needs to be regarded jointly. The project aims to make use of a new observation technique, namely SAR positioning, which can help to connect the GNSS basic network of a country to tide gauge stations and as such to link the sea level records of tide gauge stations to the geometric network. By knowing the geoid heights at the tide gauge stations in a global height reference frame with high precision, one can finally obtain absolute sea level heights of the tide gauge stations in a common reference system and can link them together. By this method, on the one hand national height systems can be connected and on the other hand the absolute sea level at the tide gauge stations can be determined. By analyzing time series of absolute sea level heights their changes can be determined in an absolute sense in a global reference frame and the impact of climate change on sea level can be quantified (e.g. by ice sheet and glacier melting, water inflow, global warming). The paper presents the main scientific questions to be addressed by the project, introduces the idea of using SAR transponders for this application and describes the observation network implemented for this feasibility study.

How to cite: Gruber, T., Ågren, J., Angermann, D., Ellmann, A., Gisinger, C., Nastula, J., Oikonomidou, X., and Poutanen, M.: Geodetic SAR for Height System Unification and Sea Level Research in the Baltics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3132, https://doi.org/10.5194/egusphere-egu2020-3132, 2020.

D1754 |
Shuang Yi and Nico Sneeuw

Global terrestrial water storage (TWS) is an indicator of the integrated impact of climate variability on the environment. Accurate assessments of global TWS also facilitate the understanding of disturbances in global sea level rise. Gravity satellite GRACE has proved to be an effective tool in monitoring global TWS changes. With the latest observations of GRACE and GRACE Follow-on, we estimated the global TWS from April 2002 to October 2019, and found contrasting variations in global TWS before and after 2010. Before 2010, the global TWS was almost stable with variations that contribute only a few millimeters of sea level change; while the stability is ceased after the 2010/11 La Nina and three drastic fluctuations of up to 10 millimeters sea level contribution have occurred since then. We find these TWS changes have a good linear relationship with the global precipitation trend, rather than the accumulation of net precipitation, indicating that the precipitation trend is the main driving force of the recent global TWS instability. We further investigate the sensitivities of TWS to precipitation in basins.

How to cite: Yi, S. and Sneeuw, N.: Emerging instability in global terrestrial water storage since 2010, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17922, https://doi.org/10.5194/egusphere-egu2020-17922, 2020.

D1755 |
Pascale Ferrage, Laurent Soudarin, and Frank Lemoine

The DORIS system recorded its first measurement on February 3rd, 1990, from the SPOT-2 remote sensing satellite. 30 years after, the system is at its best. DORIS has proven greatly valuable for geodesy and geophysics applications: measuring tectonic plate motions, determination of the rotation and the gravity parameters of the Earth, contributing to the international reference system. Technological and methodological improvements have allowed the improvement in the estimates of the positions of the DORIS tracking ground stations, the Earth rotation parameters and other geodetic variables such as the geocenter and the scale of the ITRF.
The International DORIS Service (IDS) was created in 2003 under the umbrella of the International Association of Geodesy (IAG) to foster scientific research related to the French DORIS tracking system and to deliver scientific products, mostly related to the International Earth rotation and Reference systems Service (IERS). Since its start, the organization has continuously evolved, leading to additional and improved operational products from an expanded set of DORIS Analysis Centers. IDS is now based on a reinforced structure with two Data Centers, six Analysis Centers, four Associate Analysis Centers, and a Combination Center. Using the experience gained in the preparation of the ITRFs, many improvements were made all along both in data analysis and on technical aspects. After the IDS Retreat held in June 2018, the IDS GB worked on the development of a strategic plan for the IDS. In the coming years, IDS will focus on growing the community, extending the DORIS applications, and improving the technology, the infrastructure and the processing.
This presentation addresses the recent achievements made by IDS and how the service is preparing the future.

How to cite: Ferrage, P., Soudarin, L., and Lemoine, F.: The International DORIS Service is preparing the future, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21595, https://doi.org/10.5194/egusphere-egu2020-21595, 2020.

D1756 |
Xavier Collilieux, Clément Courde, Bénédicte Fruneau, Mourad Aimar, Guillaume Schmidt, Isabelle Delprat, Damien Pesce, and Guy Wöppelmann

Geodetic observatories play a fundamental role in the determination of the International Terrestrial Reference System releases. They host several geodetic permanent instruments whose coordinates can be determined at the centimeter level or better. They comprise Global Navigation Satellite System (GNSS) permanent antenna/receivers, Satellite Laser Ranging (SLR) stations, Very Long Baseline Interferometry (VLBI) telescope and Doppler Orbitography Integrated by Satellite (DORIS) beacons. The Calern site of the Observatoire de la Côte d’Azur (OCA) is an example of such a multi-technique site located in the South of France. It hosts a DORIS beacon, a SLR/LLR station and two GNSS permanent stations.


In the process of determining coordinates of geodetic instruments in a unified reference frame, the relative positions of the instruments at co-location sites are integrated in the ITRF combination. Thanks to the additional measurements obtained from local surveys, it is possible to determine global biases between coordinates determined by individual space geodetic techniques, and express them in the same reference system. An additional fundamental assumption of the combination process is that stations located on the same site do not move with respect to each other. Spaceborne Synthetic Aperture Radar Interferometry (INSAR technique), is an interesting tool to evaluate that hypothesis as it allows measuring ground displacements in the line of sight of the satellite,  and has been used only occasionally in the past for this purpose,. Notably, the Persistent Scatterer (PS) Interferometry enables determining time series of ground displacements on particular scatterers exhibiting phase stability in a stack (or series ?) of SAR images. To ensure the existence (or presence ?) of such PS, artificial corner reflectors can be installed.


We present the procedure that we adapted from Parker et al. (2007) to install and validate the installation of a corner reflector at OCA observatory, close to the currently operating GNSS, SLR and DORIS stations, specifically designed for Sentinel-1 satellite. An initial local tie survey was carried out to assess the stability of the reflector through time.

How to cite: Collilieux, X., Courde, C., Fruneau, B., Aimar, M., Schmidt, G., Delprat, I., Pesce, D., and Wöppelmann, G.: Radar Corner Reflector installation at the OCA geodetic Observatory (France), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5201, https://doi.org/10.5194/egusphere-egu2020-5201, 2020.

D1757 |
Rüdiger Haas, Eskil Varenius, Grzegorz Klopotek, Periklis-Konstantinos Diamantidis, Saho Matsumoto, Matthias Schartner, and Jan Tobias Nilsson

The VLBI Global Observing System (VGOS) is the VLBI contribution to GGOS. During the last years, several VGOS stations have been established, the VGOS observation program has started, and by 2020 VGOS has achieved an operational state involving eight international VGOS stations. Further VGOS stations are currently installed, so that the number of active VGOS stations will increase drastically in the near future. In the end of 2019 the International VLBI Service for Geodesy and Astrometry (IVS) decided to start a new and so-far experimental VGOS-Intensive series, called VGOS-B, involving Ishioka (Japan) and Onsala (Sweden). Both sites operate modern VGOS stations with 13.2 m diameter radio telescopes, i.e. ISHIOKA (IS) in Japan, and ONSA13NE (OE) and ONSA13SW (OW) in Sweden. In total 12 VGOS-B sessions were planned to be observed between December 2019 and February 2020, one every week, in parallel and simultaneously to legacy S/X INT1 Intensive sessions that involve the stations KOKEE (KK) on Hawaii and WETTZELL (WZ) in Germany. The 1-hour long VGOS-B sessions consist of more than fifty radio source observations, resulting in about 1.6 TB of raw data that are collected at each station. The scheduling of the VGOS-B sessions is done at Vienna University of Technology using VieSched++ and the subsequent steps (correlation, fringe-fitting, database creation) are planned to be carried out at the Onsala Space Observatory using DIFX and HOPS. The resulting VGOS databases are planned to be analysed with several VLBI analysis software packages, involving nuSolve, c5++ and ivg::ASCOT. In this presentation, we give an overview on the VGOS-B series, present our experiences, and discuss the obtained results.

How to cite: Haas, R., Varenius, E., Klopotek, G., Diamantidis, P.-K., Matsumoto, S., Schartner, M., and Nilsson, J. T.: VGOS Intensives Ishioka-Onsala, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13687, https://doi.org/10.5194/egusphere-egu2020-13687, 2020.

D1758 |
Helene Wolf, Matthias Schartner, Johannes Böhm, and Andreas Hellerschmied

Observing extragalactic radio sources is an integral part of Very Long Baseline Interferometry (VLBI) but observing satellites also provides a variety of new possibilities. Interesting scientific applications can be found in providing space ties instead of using local ties for connecting reference frames of different space-geodetic techniques. To generate schedules including observations to satellites a dedicated module has been implemented in the new scheduling software VieSched++.

This newly developed module determines possible satellite observations considering several observation conditions, such as the visibility from the selected station network and antenna slew rates. A schedule including observations to quasars and satellites can be generated in a semi-automatic mode. The scheduling of the satellite scans is done manually by the user who can select and adjust the possible satellite observations before adding them to the schedule. The remaining part of the schedule is filled automatically by the software VieSched++ using the general optimization algorithm with observations to quasars. In this poster an overview of the current status of the satellite scheduling module in VieSched++ is given, as well as an outlook to highlight future plans. 

How to cite: Wolf, H., Schartner, M., Böhm, J., and Hellerschmied, A.: Satellite Scheduling with VieSched++ : current status and future plans, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13254, https://doi.org/10.5194/egusphere-egu2020-13254, 2020.

D1759 |
Ryuichi Ichikawa, Hideki Ujihara, Shinsuke Satoh, Yusaku Ohta, Basara Miyahara, Hiroshi Munekane, Taketo Nagasaki, Osamu Tajima, Kentaro Araki, Takuya Tajiri, Hiroshi Takiguchi, Takeshi Matsushima, Nobuo Matsushima, Tatsuya Momotani, and Kenji Utsunomiya

We have started to develop a next-generation microwave radiometer to be used in millimeter-wave spectroscopy for the high-resolution and high-precision monitoring of water vapor behavior. The new radiometer will be suitable for not only space geodetic techniques such as VLBI and GNSS, but also field measurements to monitor, for example, volcanic activities and cumulonimbus cloud generation. The planned front-end system for our new microwave radiometer has a wide bandwidth feed of 20–60 GHz. A signal from the feed is separated into two linear orthogonal polarized signals using an orthomode transducer (OMT); one is in the 20–30 GHz feed and the other is in the 50–60 GHz feed. We are now planning to cool the wideband feed, OMT, and LNA for each signal at 77 K using a Stirling cryocooler to improve the signal-to-noise ratio. We assembled a room-temperature 20–30 GHz receiver without the cooling system until the middle of 2019 as a first step of our development. We implemented the new receiver into the 3.7 m dish at Okinawa Electromagnetic Technology Center, National Institute of Information and Communications Technology (NICT), and carried out the first measurements using this receiver for validation tests in October 2019. Quick-look data obtained by the new receiver shows good power signals for the expected receiving band of 18–28 GHz. We are now developing another receiver for a higher band of 50–60 GHz, and we are going to implement the second one into the new prototype radiometer by the end of this fiscal year.

How to cite: Ichikawa, R., Ujihara, H., Satoh, S., Ohta, Y., Miyahara, B., Munekane, H., Nagasaki, T., Tajima, O., Araki, K., Tajiri, T., Takiguchi, H., Matsushima, T., Matsushima, N., Momotani, T., and Utsunomiya, K.: Development of novel ground-based microwave radiometer for earth science -results of the first measurements-, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18305, https://doi.org/10.5194/egusphere-egu2020-18305, 2020.

D1760 |
Allison Craddock, Gary Johnston, Felix Perosanz, Rolf Dach, Charles Meertens, Michael Moore, and Mayra Oyola

For over twenty-five years, the International Global Navigation Satellite System (GNSS) Service (IGS) has carried out its mission to advocate for and provide freely and openly available high-precision GNSS data and products.

The IGS is an essential component of the IAG’s Global Geodetic Observing System (GGOS), where it facilitates cost-effective geometrical linkages with and among other precise geodetic observing techniques, including: Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), and Doppler Orbitography and Radio Positioning Integrated by Satellite (DORIS). These linkages are fundamental to generating and accessing the International Terrestrial Reference Frame (ITRF).  As it enters its second quarter-century, the IGS is evolving into a truly multi-GNSS service, and at its heart is a strong culture of sharing expertise, infrastructure, and other resources for the purpose of encouraging global best practices for developing and delivering GNSS data and products all over the world.

This poster will present an update on current IGS products and operations, as well as highlights on recent organizational developments and community activities. The impacts and benefits of global cooperation and openly available data will be emphasized, and information about the IGS stations and network, contributions to the International Terrestrial Reference Frame solutions, and product applications will be presented. A summary of IGS products, with emphasis on analysis, coordination, applications, and their availability will be described. Information about efforts to form new groups supporting product generation within IGS open data and product policies will be included. Information about the themes and topics of discussion for the upcoming 2020 IGS Workshop in Boulder, Colorado, USA will also be provided.

How to cite: Craddock, A., Johnston, G., Perosanz, F., Dach, R., Meertens, C., Moore, M., and Oyola, M.: Twenty-Five Years of the International GNSS Service, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6153, https://doi.org/10.5194/egusphere-egu2020-6153, 2020.

D1761 |
Seiichi Shimada

GEONET tracking data is analyzed applying Galileo and/or GPS satellite systems, using GAMIT/GLOBK software. We adopt ITRF2014 reference frame and CODE precise orbit obtained in the GMEX experiment. For the fiducial sites, we use 14 IGS sites in and around East Asia both Galileo and GPS analyses. At the IGS sites in this area, number of sites, whose coordinates and velocity are determined in Altamimi et al.(2016) and also tracking Galileo satellites, is very limited. In the current version of the GAMIT/GLOBK program, the solar radiation pressure model of the Galileo satellites has limited accuracy, which results in large errors in the analysis using the Galileo satellites. Preliminary results from 10-day Galileo satellites analysis of the 2018 DOY 300-309 show that the weighted rms of the N-S component of the repeatability of 1276 GEONET site coordinates is 5.5 mm, the E-W component 4.5 mm, and the U-D component 9.0 mm. On the other hand, for those from GPS satellites show that those weighted rms of the N-S component is 1.6 mm, E-W component 1.3 mm, and U-D component 3.5 mm. Therefore, the repeatability of the GEONET site coordinate solution of the composite solution of GPS and Galileo satellites has hardly improved: the weighted rms of the N-S component is 2.7 mm, E-W component 2.0 mm, and U-D component 3.7 mm. The presentation will show the results applying the new Galileo satellite solar pressure model (ECOMC model) included in the updated GAMIT/GLOBK program released in the near future, as well as the period of analysis more than one year. 

How to cite: Shimada, S.: Data analysis of GEONET network data applying Galileo Satellite System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22256, https://doi.org/10.5194/egusphere-egu2020-22256, 2020.

D1762 |
Carine Bruyninx, Andras Fabian, Juliette Legrand, and Anna Miglio

The IGS (International GNSS Service) site log format is the worldwide standard for exchanging GNSS station metadata. It contains, among other things, a description of the GNSS site and its surroundings, the contact persons, and an historical overview of the GNSS equipment. This information is valuable for reliable GNSS data analysis and interpretation of the results.

This IGS site log is also used within the EUREF Permanent Network (EPN, Bruyninx et al., 2019) and the GNSS component of the European Plate Observing System (EPOS, https://www.epos-eu.org/). However, due to their specific needs, these networks collect additional GNSS metadata. For example, within the EPN, individual receiver antenna calibration values are collected, as well as the information on the data provided by the station. EPOS is collecting in addition data licences. Within the Creative Commons permitted licence scheme, two licences will be adopted by EPOS, CC:BY and CC:BY:NC. Both licenses require that the data user acknowledges (cites) the data owner. To facilitate this data citation, EPOS recommends attributing Digital Object Identifiers (DOI) to the GNSS data and therefore also includes the DOI in the collected GNSS station metadata.

Many IGS and EPN stations also contribute to EPOS and therefore it is imperative to harmonize the collection and distribution of the additional metadata. The GeodesyML (http://geodesyml.org) format already allows including more metadata compared to the IGS site log format. In this poster, we will review the challenges and propose how to tackle them. We will finish by showing the choices made within the “Metadata Management and Distribution System for Multiple GNSS networks” (M3G) which collects and disseminates GNSS station metadata within both the EPOS and EPN networks.

Bruyninx C., Legrand J., Fabian A., Pottiaux E. (2019) GNSS Metadata and Data Validation in the EUREF Permanent Network. GPS Sol., 23(4), https://doi: 10.1007/s10291-019-0880-9          

How to cite: Bruyninx, C., Fabian, A., Legrand, J., and Miglio, A.: GNSS Station Metadata Revisited in Response to Evolving Needs, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18634, https://doi.org/10.5194/egusphere-egu2020-18634, 2020.

D1763 |
Georgios S. Vergos, Riccardo Barzaghi, Sylvaint Bovalot, Elmas Sinem Ince, Adrian Jäggi, Mirko Reguzzoni, Hartmut Wziontek, and Kevin Kelly

Through its structure the International Gravity Field Service (IGFS) promotes the interaction, cooperation and synergy between the Gravity Services, namely the Bureau Gravimétrique International (BGI), the International Service for the Geoid (ISG), the International Geodynamics and Earth Tides Service (IGETS), the International Center for Global Earth Models (ICGEM), the International Combination Service for Time-variable Gravity Fields (COST-G) and the International Digital Elevation Model Service (IDEMS).

Furthermore, via its Central Bureau hosted at the Aristotle University of Thessaloniki (Greece), IGFS provides a link to the Global Geodetic Observing System (GGOS) Bureaus in order to communicate their requirements and recommendations to the IGFS-Centers. Moreover, IGFS provides a coordination host for the utilization of gravity-field related products and services towards their inclusion within a GGOS consistent frame meeting the necessary precision and accuracy requirements.

In this work, an outline is given on the recent activities of IGFS, namely those related to the contributions to the implementation of: the International Height Reference System/Frame; the Global Geodetic Reference System/Frame; the new Global Absolute Gravity Reference System/Frame and rhe combination of temporal monthly global gravity field models. Particularly, the impact that these activities have and will have in improving the estimation of the Earth’s gravity field, either at global and local scale, is highlighted also in the framework of GGOS.

How to cite: Vergos, G. S., Barzaghi, R., Bovalot, S., Ince, E. S., Jäggi, A., Reguzzoni, M., Wziontek, H., and Kelly, K.: The IGFS gravity field observations and products contributions to GGOS infrastructure , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10126, https://doi.org/10.5194/egusphere-egu2020-10126, 2020.

D1764 |
Christoph Förste, Elmas Sinem Ince, Sven Reissland, Kirsten Elger, Frank Flechtner, and Franz Barthelmes

The more than 15-year-old ICGEM is one of the five services coordinated by the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG). It is hosted by GFZ German Research Centre for Geosciences in Potsdam, Germany. The aim of the ICGEM service is to provide the scientific community with a state-of-the-art archive of static and time variable global gravity field models of the Earth in a standardized format with a possibility to assign DOI number. Furthermore, ICGEM contains an interactive calculation and visualization service of gravity field functionals. Development and maintenance of such a unique platform is crucial for the scientific community in geodesy, geophysics, oceanography and climatology and has a positive impact in governmental institutions and industrial practice. This poster covers the maintenance, recently established new features and future plans of the ICGEM Service. New features include the calculation of gravity field functionals at a list of user-defined distributed points and new topographic gravity field models, whereas the future plans aim to meet the needs of the scientific community. As an add-on, ICGEM provides also access to the gravity field models of some other celestial bodies (Mars, Venus, and Earth’s moon).

How to cite: Förste, C., Ince, E. S., Reissland, S., Elger, K., Flechtner, F., and Barthelmes, F.: The International Centre for Global Earth Models (ICGEM), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3511, https://doi.org/10.5194/egusphere-egu2020-3511, 2020.