Approaches to Realize and Maintain National Terrestrial Reference Frame Based on BDS Data

The realization and maintenance of the China geodetic coordinate system 2000 (CGCS2000) depends on GPS technologies, and therefore is a national security risk. BDS began offering services to customers in the Asia-Pacific region in December 2012. It provides a good opportunity to realize and maintain the national terrestrial reference frame (TRF) using BDS system. We focus on how to use BDS observations of BDS/GPS stations with dual-mode receivers to realize the National TRF, aligned to the international terrestrial reference frame (ITRF). Results show that the precision of the horizontal velocity derived from BDS data are comparable to those derived from GPS data at about 2-3 mm/a, using more than two years of observation data. The RMS of the station coordinate residuals, with the linear velocity removed, are better than 0.8 cm and 1.7 cm for the horizontals and verticals, respectively. The current precision of BDS data can allow observation of seasonal displacements in the verticals. System errors related to the longitude and latitude are found in the coordinate differences between BDS and GPS data based on PPP mode. Thus, the current BDS system can be used to realize and maintain the national terrestrial reference frame at cm level.