Regional Orbit Improvement Techniques Applied to a Japanese Fixed-Point GPS Network

Abstract

Bock and Shimada (1990) introduced the concept and some experimental examples of the GPS fixed-point networks for deformation measurements. The measurement applying such a fixed-point GPS network is one of the promising technique to monitor crustal movements for the purpose of geodynamic study. The Kanto-Tokai ten-point dedicated, GPS fixed-point network (NIED network) in central Japan is the first one of those networks in the world, established in April 1988 (Shimada et al., 1989). Shimada and Bock (1991) estimated the positions of the NIED network sites with respect to the terrestrial reference frame using world-wide GPS tracking data collected during the Global Orbit Tracking Experiment (GOTEX-1) campaign carried out in November 1988. They then computed the positions of the network stations from the first sixteen months of network data by applying weighted constraints on the site positions and on the available satellite ephemerides (“regional orbit improvement techniques”) and a simultaneous two-session analysis for each data window, and obtained crustal deformations during the initial sixteen months of data. In the analysis, they used the GAMIT GPS software developed at Massachusetts Institute of Technology and Scrips Institution of Oceanography (King and Bock, 1991). They demonstrated the validity of the regional orbit improvement techniques for the fixed-point regional network, reducing the cost required to obtain the regional deformations and the measurement error caused by the broadcast orbit ephemeris.