The BDS-3 navigation satellite system of China was completely accomplished in July 2020,then starting to provide services for global users.GNSS stations in the China seismic experiment site(CSES)have been receiving BDS-3 satellite data ever since,and accumulated observational data for more than 2 years,providing an important platform in acquiring observa-tional data for the application of BDS-3 in exploring crustal movement in Sichuan-Yunan area.To assess the current precision of the BDS-3 positioning and its performance in crustal movement monitoring,we first evaluate the quality of BDS-3 observational data according to the relationship of multi-path effect and signal-to-noise ration with elevation angles.Using GAMIT/GLOBK(version 10.7),we have processed the simultaneously recorded BDS-3 and GPS data separately to obtain coordinate time series for each station.Fitting the time series of three coordinate components separately with a functional model which encompasses linear,annual,semi-annual and other terms by the maximum probability estimation method,we obtain velocity,amplitude and phase for E,N and U components of the coordinate time series.Furthermore,we evaluate the precision of BDS-3 and GPS by comparative analysis of the fitting results.Finally we discuss the possible factors which could influence the positioning precision of BDS-3,and regional features of the horizontal velocity field derived from BDS-3 observations.The results show that the quality of raw data for BDS-3 observations is comparable with GPS data.The data fitting for BDS-3 and GPS time series shows that the average value of root mean square(RMS)of the BDS-3 residual time series are 4.42,4.25 and 8.34 mm for the E,N and U components,respectively,larger than those of GPS data.Systematic difference is identified of about 2 mm/a in E direc-tion between velocity fields of BDS-3 and GPS.The velocity fields,and the annual and semi-annual signals derived from BDS-3 and GPS data do not show obvious differences in regional distribution.We think that currently the factors affecting the posi-tioning precision of BDS-3 are the relatively lower precision of satellite orbit and clock difference products,the shortage of em-pirical solar pressure and satellite antenna phase center correction for BDS-3 and so on.The difference between the velocity fields of BDS-3 and GPS is due to the inconsistence of their reference frames.We expect that,with the continuous accumulation of BDS-3 observational data and the improvement of the data processing models,the positioning precision of BDS-3 will en-hance with time,and the BDS-3 will be used independently from GPS to provide geodetic products of high-precision for monito-ring crustal movement at CSES.
维普
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