The Preliminary Realization and Evaluation of CTRF2020 Based on New BDS3 Technology

The current research of the international and regional coordinate reference framework is mainly realized by GPS technology. The launch of the last BDS3 satellite on June 23 of 2020 marked the completion of the global deployment of BDS. Therefore, it is urgent to study and establish the corresponding coordinate reference framework. We aim to preliminarily realize and evaluate the BDS3/COMPASS terrestrial reference framework (CTRF2020). CTRF2020 reference epoch is 2020.0, and it can be expressed with the coordinates and velocities of a series of reference sites at the epoch of 2020.0. Firstly, the evaluation of the actual service performance of BDS in the global region reflects the high visibility and change trend of BDS satellite in recent three years, which provides basic input data for CTRF2020. Then, the BDS observations of about 100 global stations in the recent three years are calculated by PPP and NET solution, to obtain the global high-precision BDS coordinate time series. Then, the BDS time series of the two solutions are fitted and compared with the IGS14 velocity field. The results show that the series accuracy of PPP-BDS and NET-BDS solutions is equivalent, and there is an mm-level systematic deviation with IGS14 solutions. The horizontal series fitting accuracy of PPP-BDS and NET-BDS solutions is better than that of the vertical direction, the accuracy of NET-BDS solution is slightly better than PPP-BDS, and the difference of fitting accuracy is 0.12, 0.13, and 0.50 mm in the NEU direction. The velocity field accuracy of PPP-BDS and NET-BDS solution is the same, and the overall three-dimensional velocity difference is less than 0.2 mm/a. The velocity fields of PPP-BDS and NET-BDS solution have little difference from IGS14, and the overall difference is less than 0.5 mm/a. Finally, we give the limitations and improvement direction of CTRF2020. The preliminary realization and evaluation of CTRF2020 may be expected to provide a reference for the future realization of a comprehensive terrestrial reference framework dominated by BDS3 technology and supplemented by multi-source space geodetic technology.