ALBERT

Description: This presentation covers the 10 year history of GGOS Japan. As many as six Japanese national institutes have been operating large-size geodetic facilities with VLBI and/or SLR in Japan and also in Antarctica, and they had been involved in each geodetic service rather independently. In 2013, we initiated "GGOS Working Group" in Japan to enhance the communications among the Japanese institutes and global geodesists and also to encourage collaboration beyond each technique. GGOS Japan is basically a loose network, but it has a chair, a secretary, an outreach representative, working groups (currently active: Data DOI working group) and representatives of each geodetic technique (VLBI, SLR/LLR, GNSS, DORIS and gravimetry). We regularly host annual meetings and sometimes small meetings with focused issues. We have also involved in organising or supporting scientific sessions in domestic and international conferences. During the 10 years history, it was positioned as a GGOS Affiliate in 2017 and we renamed it as "GGOS Japan" in 2019. Basara Miyahara was elected as the GGOS President in 2019. GGOS Japan's webpages are being updated on the GGOS Website, and we have contributed to GGOS YouTube channels. We often set focused activities. We are currently working on the review of ITRF2020 from an operating point of view, and we are also working on a possible best location for a future GGOS Cores site in Japan. In the future we hope to collaborate with international communities, in particular with other GGOS Affiliates.

Description: The Geospatial Information Authority of Japan (GSI) has operated two space geodetic techniques, VLBI and GNSS, at the Ishioka Geodetic Observing Station (hereafter Ishioka). We regularly conduct local-tie surveys to determine the local-tie vector connecting those techniques. In 2021, we submitted the results of the surveys to the International Earth Rotation and Reference Systems Service (IERS) to contribute to the construction of the International Terrestrial Reference Frame (ITRF). In ITRF2020, Ishioka was registered as one of the IERS stations for the first time. Reference points of VLBI antennae generally cannot be measured directly and thus need to be estimated in the local-tie survey. In Ishioka, we estimate the position of the reference point of the VLBI antenna by a method called the ‘inside method’, in which targets attached to the inner wall of the azimuth cabin are used for observation. This method is applied only to the specific antenna with an observation pillar constructed in it, but this method is effective to improve efficiency of local-tie survey. We combine the results of the inside-method observation and various other observations using total stations, geodetic leveling and static GNSS, and calculate the local-tie vector with the software called pyaxis. In this report, we will compare the local-tie vector obtained from the surveys with that derived from the ITRF2020 after describing the outline of the local-tie survey technique at Ishioka.