Local tie survey of the SLR and GNSS stations at the Shimosato Hydrographic Observatory

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.