Applying recent 10-year GPS measurement data from some nationwide GPS networks, several regional GPS monitoring networks and the Asia-Pacific Regional Geodetic Project (APRGP), this paper gives out a combined, consistent and unified velocity field solution in ITRF97 by rotation transformation of regional GPS network results. In order to study the characteristics of present-time intra-plate crustal deformation of China, we have constructed a new present-time plate motion model named ITRF97VEL. The model can better describe present-time features of global plate motion than the geological model NNR-NUVEL1A. Based on the present time plate motion model ITRF97VEL, deformation velocities of more than 260 GPS sites are determined. The results show the crustal motion in China is especially inhomogeneous. The crustal deformation in the west of China is far stronger and more complicated than that in the east of China taking the N-S seismic belt of China as a boundary. The deformation velocity gradually reduces from south to north in the west of China by energy release in several W-E direction arc suture zones. The Qinghai-Xizang Plateau is shortening in north-south direction and extending in west-east direction due to the strong shove of Indian plate.The shortening of about 15 mm/a and 9-13 mm/a is accommodated across Hymalayan block and the west Tian Shan respectively. Within southern Tibet,between the longitudes of 80 • E to 91 • E,there is E-W extension of 20.2±1.2 mm/a. The slip rates of KJFZ in south Tibet and Altyn Tagh fault are 2-3 mm/a and 4-6 mm/a respectively. Our GPS results indicate there is a less than 7 mm/a shortening within the Longmen Shan. These results support the supposition of crustal thickening.

Quality control systems for satellite laser ranging observations have been developed at a number of analysis institutes worldwide, using various software packages of precise orbit determination and data analysis. Satellite laser range observations, primarily from the two LAGEOS satellites but also from other satellites in low-Earth-orbits and up to GNSS altitude, are being processed on a sub-daily to weekly basis. The generated quality control reports are widely used to detect various kinds of problems and quickly provide anomalous information to laser ranging stations. They have been effective in shortening the time to return to normal when anomalous data are detected and in quantifying the performance of laser ranging stations. Consequently, a rapid feedback loop has now been incorporated in the modern satellite laser ranging operation.

No abstract

No abstract

Chinese BeiDou Navigation Satellite System (BDS) as a mixed constellation, consists of not only Medium Earth Orbit (MEO) satellites but also Inclined Geosynchronous Orbit (IGSO) and Geostationary Earth Orbit (GEO) satellites, of which the GEO satellites remain visible and stationary in the Asia-Pacific region almost all the time so as to better ensure the reflected signals' stability and continuity, compared to using only MEO satellites in previous GNSS-R remote sensing research. This paper demonstrates ocean altimetry capability using reflected signals from BDS GEO satellite with coastal experiments conducted in Weihai, Shandong, China on July 6 and July 9, 2019. By using only one GEO satellite, the precision of DDM (Delay Doppler Map) and phase altimetry is up to decimeter (close to millimeter) level. And the results show that BDS GEO-R technique can be used to monitor small changes in ocean altimetry with high temporal resolution.