The Development of the New Analysis Strategy of GEONET

Abstract:

1. Overview of GEONET and its analysis strategy

Geospatial Information Authority of Japan has operated a dense GNSS observation network system, named GEONET, which consists of more than 1,300 CORS covering most region of Japan. The daily coordinate of each site from 1996 is calculated by the 4th analysis strategy developed in 2009 and is provided as the “F3 solution” via FTP site. Nowadays, F3 coordinate is vital infrastructure not only for crustal deformation monitoring but also for location based service and various scientific activities. We are now developing the new strategy in order to provide more accurate coordinates aligned to ITRF2014. The preliminary results named "F5 solution" were released on March 24th, 2020 in advance of the official edition. In our poster, we will give an overview of our new strategy and show the remarkable differences between F3 and F5 coordinates with some examples.

2. Differences between F3 and F5 coordinates

2.1. The reference frame

ITRF2014 (IGS14) is employed in the new analysis strategy instead of ITRF2005 (IGS05), which is used in the current strategy. There has been a clear discrepancy between them due to the co- and post-seismic deformation of the 2011 Tohoku-oki earthquake and the improvement of space geodesy technique. Comparing with the IGS daily SINEX coordinates, which is aligned to ITRF2014 (IGS14/IGb14), systematic offset of about 2cm appeared in F3 is removed at TSKB (see the figure below).

2.2. The reference site analysis

The coordinates of each GEONET site is estimated with fixing the particular GEONET site named Tsukuba-1. The coordinates of Tsukuba-1 sometimes jump up because only a small number of fiducial sites located in the East Asia are used for the analysis and the observation data in those sites sometimes misses. In order to generate the stable time series data of the fixed site, we increase the number of fiducial site covering not only East Asia but also whole earth in the new strategy.

3. Future perspective

The official results will be released in 2021FY and will include the data of 1990s and 2000s though the data period of preliminary results starts from January 2017. We keep on processing the past data and evaluating them until the official release.