G2.1

The Global Geodetic Observing System (GGOS) is the contribution of Geodesy to the observation and monitoring of the Earth System. Geodesy is the science of determining and representing the shape of the Earth, its gravity field and its rotation as a function of time. A core element to reach this goal are stable and consistent geodetic reference frames, which provide the fundamental layer for the determination of time-dependent coordinates of points or objects, and for describing the motion of the Earth in space. Traditionally, geodetic reference frames have been used for surveying, mapping, and space-based positioning and navigation. With modern instrumentation and analytical techniques, Geodesy is now capable of detecting time variations ranging from large and secular scales to very small and transient deformations with increasing spatial and temporal resolution, high accuracy, and decreasing latency. GGOS has been working closely with components of International Association of Geodesy (IAG) to provide consistent and openly available observations of the spatial and temporal changes of the shape and gravity field of the Earth, as well as the temporal variations of the Earth’s rotation. These efforts make available a global picture of the surface kinematics of our planet, including the ocean, ice cover, continental water, and land surfaces, as well as estimates of mass anomalies, mass transport, and mass exchange in the System Earth. Surface kinematics and mass transport together are the key to global mass balance determination, and are an important contribution to understanding the energy budget of our planet. In order to play its vital role, GGOS has following missions; 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 geodetic 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, c) to benefit science and society by providing the foundation upon which advances in Earth and planetary system science and applications are built. For the mission, GGOS works tighter with components of the IAG, more specifically, IAG Services, IAG Commissions and IAG Inter-Commission Committees. The IAG Services provide the infrastructure and products on which all contributions of GGOS are based, and the IAG Commissions and IAG Inter-Commission Committees provide expertise and support to address key scientific issues within GGOS. Together with the IAG components, GGOS provides the fundamental infrastructure underpinning Earth sciences and their applications.

How to cite: Miyahara, B., Sánchez, L., and Sehnal, M.: The Global Geodetic Observing System (GGOS) – infrastructure underpinning Earth science, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3927, https://doi.org/10.5194/egusphere-egu21-3927, 2021.

This presentation gives a summary of the role and the activities of the Bureau of Products and Standards (BPS) to support IAG’s Global Geodetic Observing System (GGOS) in its goal to provide observations and consistent geodetic products needed to monitor, map and understand changes in the Earth’s shape, rotation and mass distribution. In its present structure, the two Committees “Earth System Modeling” and “Essential Geodetic Variables” as well as the Working Group “Towards a consistent set of parameters for the definition of a new GRS” are associated with the BPS. A key objective of the BPS is to keep track and to foster homogenization of adopted geodetic standards and conventions across all IAG components as a fundamental basis for the generation of consistent geometric and gravimetric products. Towards this aim, an updated 2^nd version of the BPS inventory of standards and conventions used for the generation of IAG products has been published in the Geodesist’s Handbook 2020. In the framework of the renewing of the GGOS website, the BPS supports the GGOS Coordinating Office in particular regarding the representation of geodetic products. Furthermore, the BPS contributes to the rewriting of the IERS Conventions as Chapter Expert for Chapter 1 “General definitions and numerical standards” and interacts with external stakeholders regarding standards and conventions, such as ISO, IAU, BIPM, CODATA and the UN GGIM Subcommittee on Geodesy, including its Working Group “Data Sharing and Development of Geodetic Standards”.

How to cite: Angermann, D., Gruber, T., Gerstl, M., Heinkelmann, R., Hugentobler, U., Sanchez, L., and Steigenberger, P.: The GGOS Bureau of Products and Standards, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4684, https://doi.org/10.5194/egusphere-egu21-4684, 2021.

Data publications with digital object identifiers (DOI) are best practice for FAIR sharing data. Originally developed with the purpose of providing permanent access to (static) datasets described in scholarly literature, DOI today are more and more assigned to dynamic data. These DOIs are providing a citable and traceable reference of 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 on Publishing Data in the Earth, Space and Environmental Sciences (COPDESS) and the Enabling FAIR Data project, data with assigned DOIs are fully citable in scholarly literature and many journals require the data underlying a publication to be available – even before accepting an article. Initial metrics for data citation allows data providers to demonstrate the value of the data collected by institutes and individual scientists.

This is especially relevant for the geodesy, because, geodesy researchers are often much more involved in operational aspects and data provision than researchers in other fields might be. Therefore, compared to other scientific disciplines, geodesy researchers appear to be producing less “countable scientific” output. Consequently, geodesy data and equipment require a structured and well-documented mechanism which will enable citability, scientific recognition and reward that can be provided by assigning DOI to data and data products.

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” in 2019. This 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.

The main objectives and activities of this working group are:

• (1) to identify what the community needs from consistent usage of DOIs for data in terms of being able to discover data, permanently cite data, and acknowledge the data providers
• (2) to develop recommendations for DOI minting strategies for different geodetic data types and granularity across IAG Services (static, dynamic, observational data, data products, combination products, networks)
• (3) to develop recommendations for a consistent method for data citation across all IAG Services, to support data providers, and to provide quantitative support detailing the use of geodetic datasets and other resources.
• (4) to develop recommendations for connecting metadata standards for data discovery (e.g. DataCite, ISO19115) with community metadata standards (GeodesyML, Station Logs)

This presentation will provide an update on recent topics and first recommendations from the GGOS DOI Working Group.

How to cite: Elger, K. and the GGOS DOI Working Group: News from the GGOS DOI Working Group, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15081, https://doi.org/10.5194/egusphere-egu21-15081, 2021.

In the correction for polar motion, terrestrial gravimetry and 3-D positioning follow different conventions. The 3-D positions were first corrected to refer to the "mean pole" (IERS Conventions up to 2010) and now to the "secular pole" (IERS Conventions update since 2018). In any case, the pole reference evolves in time and describes the track of secular or low-frequency polar wander. However, since 1988 terrestrial gravimetry follows the IAGBN (International Gravity Basestation Network) Processing Standards where the gravity values are corrected to refer to the IERS Reference Pole, a fixed quantity. This may lead to discrepancies when for instance gravity change rates from absolute gravity measurements are interpreted together with vertical velocities from GNSS. I discuss the size and geographical distribution of the possible discrepancies and how to account for them in geodynamical problems. The fixed reference of the IAGBN Processing Standards has served the gravity community well, by providing a stable system for terrestrial gravity for the last 30 years during which time the pole reference in the IERS Conventions has been revised several times. In fact, the recently proposed conventions for the International Gravity Reference System (IGRS) and the International Gravity Reference Frame (IGRF) maintain the IAGBN principle. However, it appears that with the adoption of the “secular pole” the reference in 3-D positioning may have become predictable for the foreseeable future. Therefore, it could be suggested that now is the time to harmonize terrestrial gravity with 3-D, by adopting the time-dependent secular pole as a reference for it as well, especially as this is already happening with satellite gravity. I argue that at present the practical drawbacks from such a change of reference would outweigh any theoretical advantages, and the harmonization, where necessary, can be simply performed a-posteriori to published gravity trends/values.

How to cite: Mäkinen, J.: On the correction for polar motion in gravimetry and in 3-D positioning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1853, https://doi.org/10.5194/egusphere-egu21-1853, 2021.

The International Association of Geodesy (IAG), as the organisation responsible for advancing Geodesy, introduced in 2015 the International Height Reference System (IHRS) as the global conventional reference system for the determination of gravity field-related vertical coordinates. The definition of the IHRS is given in terms of potential parameters: the vertical coordinates are geopotential numbers (C_P = W₀ ‐ W_P) referring to an equipotential surface of the Earth's gravity field realised by the conventional value W₀ = 62 636 853.4 m²s^‐2. The spatial reference of the position P for the potential W_P = W(X) is given by coordinates X of the International Terrestrial Reference Frame (ITRF). At present, the main challenge is the realisation of the IHRS; i.e., the establishment of the International Height Reference Frame (IHRF): a global network with regional and national densifications, whose geopotential numbers referring to the global IHRS are known. According to the objectives of the IAG Global Geodetic Observing System (GGOS), the target accuracy of these global geopotential numbers is 3 x 10^-2 m²s^-2. In practice, the precise realisation of the IHRS is limited by different aspects; for instance, there are no unified standards for the determination of the potential values W_P; the gravity field modelling and the estimation of the position vectors X follow different conventions; the geodetic infrastructure is not homogeneously distributed globally, etc. This may restrict the expected accuracy of 3 x 10^-2 m²s^-2 to some orders lower (from 10 x 10^-2 m²s^-2 to 100 x 10^-2 m²s^-2). This contribution summarises advances and present challenges in the establishment of the IHRS/IHRF.

How to cite: Sanchez, L., Huang, J., Barzaghi, R., and Vergos, G. S.: Towards a Global Unified Physical Height System, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1500, https://doi.org/10.5194/egusphere-egu21-1500, 2021.

The maintenance of leveling benchmark is both laborious and costly due to distortions caused by geodynamic activities and local deformations. It is necessary to realize geoid-based vertical datum, which also enables calculation from ellipsoidal heights obtained from GNSS to orthometric heights that have physical meaning. It can be considered as an important step for height system unification as it eliminates the problems stem from the conventional vertical datum. The ongoing height modernization efforts in Turkey focus to improve quality and coverage of the gravity data, eliminate errors in existing terrestrial gravity measurements in order to achieve a precise geoid model. Accuracy of the geopotential model is crucial while realizing a geoid model based vertical datum as well as unifying the regional height systems with the International Heights Reference System. In this point of view, we assessed the accuracies of recently released global geopotential models including XGM2019e_2159, GECO, EIGEN-6C4, EGM2008, SGG-UGM-1, EIGEN-6C3stat, and EIGEN-6C2 using high order GNSS/leveling control benchmarks and terrestrial gravity data in Turkey. The reason for choosing these models in the validations is their relatively higher spatial resolutions and improved accuracies compared to other GGMs in published validation results with globally distributed terrestrial data. The GNSS/leveling data used in validations include high accuracy GNSS coordinates in ITRF datum with co-located Helmert orthometric heights in regional vertical datum. 100 benchmarks are homogeneously distributed in the country with the benchmarks along the coastlines. In addition, the terrestrial gravity anomalies with 5 arc-minute resolution were also used in the tests. In order to have comparable results, residual terrain effect has been restored to the GGM derived parameters. Numerical tests revealed significant differences in accuracies of the tested GGMs. The most accurate GGM has the comparable performance with official regional geoid model solutions in Turkey. The drawn results in the study were interpreted and discussed from practical applications and height system unification points in conclusion.

How to cite: Çevikalp, M. R., Erol, B., Mutlu, B., and Erol, S.: Accuracy Assessment of Recent High-Degree Global Geopotential Models Using Geodetic Control Points and Terrestrial Gravity Data in Turkey, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11929, https://doi.org/10.5194/egusphere-egu21-11929, 2021.

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 2021 VGOS has achieved an operational state involving nine international VGOS stations. Further VGOS stations are currently being 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 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. These 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 was done using VieSched++ and the subsequent steps (correlation, fringe-fitting, database creation) were carried out at the Onsala Space Observatory using DIFX and HOPS. The resulting VGOS databases were  analysed with several VLBI analysis software packages, involving nuSolve, c5++ and ASCOT. In this presentation, we give an overview on the VGOS-B series, present our experiences, and discuss the obtained results. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X Intensive sessions (INT1/INT2), as well to the final values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin~B. 
The VGOS-B series achieve 3-4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X INT series.  Furthermore, the root mean square (RMS) agreement with respect to the IERS Bulletin B is 30-40 % better for the VGOS-B results than for the INT1/INT2 results.

How to cite: Haas, R., Varenius, E., Diamantidis, P.-K., Matsumotu, S., Schartner, M., and Nilsson, T.: VGOS Intensives Ishioka-Onsala, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12916, https://doi.org/10.5194/egusphere-egu21-12916, 2021.

Geospatial Information Authority of Japan has a VLBI antenna (ISHIOKA) and an IGS station (ISHI) at the Ishioka Geodetic Observing Station. The Ishioka VLBI antenna has participated in the IVS sessions and IGS station ISHI has continuously provided the GNSS data.

We conducted co-location surveys in November 2018 and September 2020 to determine a local tie vector between the Ishioka VLBI antenna and the IGS station ISHI. In the surveys, we determined the position of ISHI w.r.t. four surrounding reference pillars by angle/distance measurements and leveling. To determine the position of the VLBI antenna reference point w.r.t. the pillars, we adopted the “inside method” (Munekane, 2019), where the position of the VLBI reference point is determined by observing mirror installed inside the AZ cabin from the fixed point inside the cabin; its position is determined by angle/distance measurements from the pillars. We plan to finish the calculation early this year and submit the results to IERS ITRS Center so as to contribute to the ITRF2020.

In this presentation, we will outline the inside method and compare the results in 2018 and 2020.

How to cite: Takagi, Y., Ueshiba, H., Nakakuki, T., Matsumoto, S., Hayashi, K., Yutsudo, T., Mori, K., and Kobayashi, T.: VLBI-GNSS co-location survey at the Ishioka Geodetic Observing Station in 2018 and 2020, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-810, https://doi.org/10.5194/egusphere-egu21-810, 2021.

A growing number of geodetic VLBI stations participate in the VLBI Global Observing System (VGOS). Multiple sites operate both new VGOS telescopes and legacy S/X VLBI telescopes. At Onsala Space Observatory, Sweden, we operate two 13.2 m diameter VGOS radio telescopes, ONSA13NE (OE) and ONSA13SW (OW), as well as the 20~m legacy S/X telescope ONSALA60 (ON). Transitioning from the legacy system and providing continuity of the terrestrial and celestial reference frames necessitate establishing ties between S/X and VGOS telescopes. Since spring 2019, we have carried out more than 20 short-baseline (550 m) interferometric observations at X-band to establish local-tie vectors between ON, OE and OW. The obtained data were correlated at Onsala Space Observatory using DiFX, post-processed using HOPS and analysed with nuSolve and ASCOT. In this presentation we given an overview of the observations, analysis, and results of these local-tie experiments. We investigate the impact of modeling e.g. gravitational deformation, and the possibility of using phase-delays to improve the precision. Finally, we present a comparison with preliminary results from two other methods: global mixed-mode observations and classical local-tie measurements.

How to cite: Varenius, E., Haas, R., Diamantidis, P., and Nilsson, T.: Short-baseline interferometry at Onsala Space Observatory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14266, https://doi.org/10.5194/egusphere-egu21-14266, 2021.

Over the last years, ideas have been proposed to install a Very Long Baseline Interferometry (VLBI) transmitter on one or more satellites of the Galileo constellation. Satellites transmitting signals that can be observed by VLBI telescopes provide the opportunity of extending the current VLBI research with observations to geodetic satellites. These observations offer a variety of new possibilities such as high precision tying of space geodetic techniques but also the direct determination of the absolute orientation of the satellite constellation with respect to the International Celestial Reference Frame (ICRF) and have implications on the determination of long-term reference frames. 

This contribution provides a visibility study of the Galileo satellites from a VLBI network. The newly developed satellite scheduling module in VieSched++ is used to determine the time periods during which a satellite is observable from a VLBI network. The possible satellite observations are evaluated through the number of stations from which a satellite is observable. Moreover, the impact on determining the orientation of the satellite constellation, caused by the observation geometry, is investigated with using the UT1-UTC Dilution of Precision (UDOP) factor.

How to cite: Wolf, H., Böhm, J., Schartner, M., and Hugentobler, U.: Visibility study of Galileo satellites from a VLBI network, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5824, https://doi.org/10.5194/egusphere-egu21-5824, 2021.

Recently, the GNSS-A (Global Navigation Satellite System – Acoustic combination technique) seafloor geodetic observation technology, developed in the Hydrographic and Oceanographic department in Japan Coast Guard (JCG), was upgraded to be able to monitor a subseafloor interplate coupling condition of about 1 cm/year and an interplate shallow slow slip event of about 5 cm (e.g., Yokota et al., 2018, Scientific Data; Ishikawa et al., 2020, Front. Ear. Sci.). By observing such small-scale seafloor crustal movements, GNSS-A technology makes a decisive contribution to subduction seismology and disaster prevention sciences (e.g., Yokota et al., 2016, Nature; Yokota and Ishikawa, 2020, Sci. Adv.). This technology was achieved by connecting high-precision underwater acoustic ranging technology and high-rate GNSS on a vessel at sea surface.

The GNSS-A, which is carried out all over the world, especially in the Pacific Rim, has been constructed for observation of plate boundary subduction processes and fault movement processes. Unlike the GNSS network, GNSS-A has never contributed to global geodesy within the framework of the Global Geodetic Observing System (GGOS). However, it can be a unique observation method for the construction of the International Terrestrial Reference Frame (ITRF). It can make an important contribution in determining the movement and Euler pole on an oceanic plate that have few land area.

In the future, if an extensive seafloor geodetic observation network as shown by Kato et al. (2018, JDR) will be established, there is a possibility of constructing a next-generation reference frame that completely explains the plate motion on the earth's surface. This presentation will present the current state of the GNSS-A ability and cost and future prospects for the contribution to global geodesy.

How to cite: Yokota, Y., Ishikawa, T., Watanabe, S., and Nakamura, Y.: GNSS-A seafloor geodetic observation capability in 2021 and its applicability to global geodesy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4527, https://doi.org/10.5194/egusphere-egu21-4527, 2021.

Atmospheric waves excited by strong surface explosions, both natural and anthropogenic, often disturb upper atmosphere. In this letter, we report an N-shaped pulse with period ~1.3 minutes propagating southward at ~0.8 km/s, observed as changes in ionospheric total electron content using continuous GNSS stations in Israel and Palestine, ~10 minutes after the August 4, 2020 chemical explosion in Beirut, Lebanon.  The peak-to-peak amplitude of the disturbance reached ~2% of the background electrons, comparable to recently recorded volcanic explosions in the Japanese Islands. We also succeeded in reproducing the observed disturbances assuming acoustic waves propagating upward and their interaction with geomagnetic fields.

Keywords: Chemical explosion, Beirut, N-shaped pulse, Total electron content

How to cite: Kundu, B., Senapati, B., Matsushita, A., and Heki, K.: Atmospheric wave energy of the 2020 August 4 explosion in Beirut, Lebanon, from ionospheric disturbances, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1936, https://doi.org/10.5194/egusphere-egu21-1936, 2021.

The huge amount of water vapor in the atmosphere caused disastrous heavy rain and floods in early July 2018 in SW Japan. Here I present a comprehensive space geodetic study of water brought by this heavy rain done by using a dense network of Global Navigation Satellite System (GNSS) receivers. 

First, I reconstruct sea level precipitable water vapor above land region on the heavy rain. The total amount of water vapor derived by spatially integrating precipitable water vapor on land was ~25.8 Gt, which corresponds to the bucket size to carry water from ocean to land. I then compiled the precipitation measured with a rain radar network. The data showed the total precipitation by this heavy rain as ~22.11 Gt.

Next, I studied the crustal subsidence caused by the rainwater as the surface load. The GNSS stations located under the heavy rain area temporarily subsided 1-2 centimeters and the subsidence mostly recovered in a day. Using such vertical crustal movement data, I estimated the distribution of surface water in SW Japan. 

The total amount of the estimated water load on 6 July 2018 was ~68.2 Gt, which significantly exceeds the cumulative on-land rainfalls of the heavy rain day from radar rain gauge analyzed precipitation data. I consider that such an amplification of subsidence originates from the selective deployment of GNSS stations in the concave places, e.g. along valleys and within basins, in the mountainous Japanese Islands.

How to cite: Arief, S.: Topographic amplification of crustal subsidence by the rainwater load of the 2018 heavy rain in SW Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16260, https://doi.org/10.5194/egusphere-egu21-16260, 2021.

The Metadata Management and Distribution System for Multiple GNSS Networks (M³G, https://gnss-metadata.eu), hosted by the Royal Observatory of Belgium, is one of the services of the European Plate Observing System (EPOS, https://www.epos-eu.org) and EUREF (http://euref.eu).

M³G provides the scientific as well as the non-scientific community with a state-of-the-art archive of information on permanently tracking GNSS stations in Europe, including the station description, the GNSS networks the stations contribute to, whether station observation data are publicly available, and how to access them. 

Since its first public release (2018), M³G has been under continuous development, to respond to the evolving needs of the GNSS community, to progress towards FAIR data principles and comply with GDPR. 

M³G offers APIs and an interactive user interface where any GNSS station manager, after registration, can insert all information relative to its GNSS stations and make this information publicly available. Consequently, the commitment of station managers to insert GNSS station metadata in M³G and their willingness to keep the information up to date is crucial for the success of M³G.

At the moment, M³G is used by 127 GNSS agencies and includes data from more than 2500 GNSS stations all over Europe, and more still in the process of being collected.

We will illustrate the rationale underlying M³G, the data that it provides and how these data can be accessed.

How to cite: Fabian, A., Bruyninx, C., Miglio, A., and Legrand, J.: M3G: an expanding catalogue of permanently tracking GNSS stations in Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11655, https://doi.org/10.5194/egusphere-egu21-11655, 2021.

The Japan Coast Guard (JCG) operates Satellite Laser Ranging (SLR) and GNSS observation at the Shimosato Hydrographic Observatory (SHO) in Wakayama Prefecture, Japan. The SLR and GNSS observation results obtained at the SHO are submitted to the ILRS and the IGS, respectively, and have contributed to the development of the International Terrestrial Reference Frame (ITRF). The SHO, operating two types of global geodetic observation, is now one of the sites of the Global Geodetic Observing System (GGOS).

Observation sites such as the SHO that operate multiple geodetic techniques function as co-location sites, where the different geodetic techniques can be linked together by precisely determining the local tie between these techniques. In November 2020, the JCG and the Geospatial Information Authority of Japan (GSI) have performed a local tie survey at the SHO to determine the local tie between the SLR telescope and the GNSS station. In our survey, we mounted several targets on the SLR telescope, which we observed from four survey sites that were temporarily set in the SHO. During the survey, we rotated the telescope along the azimuth and the elevation axes at fixed intervals, observing the target positions for each rotation angle. The measured target positions form arcs, from which we can estimate the rotation axes of the telescope; the origin of the axes was determined as the center of the SLR telescope. For the calculation of the local tie, we used the software pyaxis, developed by Land Information New Zealand (LINZ).

In our presentation, we will show the methods of our survey and calculation described above, and the estimated local tie vector. As of January 2021, we are preparing to submit the co-location SINEX file to the IERS, to contribute to the construction of the upcoming ITRF2020.

How to cite: Watanabe, S., Nakamura, Y., Yokota, Y., Suzuki, A., Ueshiba, H., and Seo, N.: Local tie survey of the SLR and GNSS stations at the Shimosato Hydrographic Observatory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4544, https://doi.org/10.5194/egusphere-egu21-4544, 2021.

National Centre for Geodesy (NCG) has been established in IIT Kanpur, India with the vision of acting as a hub of excellence in geodetic research at the National and International level. Working towards its mission, it has initiated this state-of-the- art establishment for improving the space geodetic infrastructure of the country and encouraging more researches in the geodesy field. The presentation will discuss the current status of the planned core site and its future establishments. It will provide detailed description of all the facilities installed in the site right now, and the future extensions. This new core-site will house facilities for three technologies – Space, Time and Earth gravity domain. The main purpose of establishing this site is for improving the realization of terrestrial and celestial reference frames, Earth Orientation Parameters (EOPs) and other data products essential for understanding the Earth’s environment. This co-located site with four space geodetic techniques will help in the International campaign for determination of TRF with 1mm accuracy and 0.1 mm/yr. stability. Moreover, this site location will improve the uniformity in geographical distribution of the ITRF observatories and the necessity of this station has been confirmed by simulation modelling.

Keywords: NCG, India, Core site, TRF, stability, uniformity.

How to cite: Dhar, S., Tiwari, A., Balasubramanian, N., Devaraju, B., Dikshit, O., Prakash, J., Mishra, P., Agarwal, D., Sharma, V., Varade, D., Laha, A., Kumar, A., Singh, S., Bihari Narayan Singh, A., Goyal, R., and Kumar, V.: Establishment of State-of-the-Art Geodesy Village in India: Current status and Outlook, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16068, https://doi.org/10.5194/egusphere-egu21-16068, 2021.