Initial Assessment of the BDS-3 PPP-B2b RTS compared with the CNES RTS

Abstract

In 2020, the BeiDou navigation satellite system (BDS) initiated a real-time service (RTS) for precise point positioning (PPP) using the B2b signal for users in China and its surrounding areas. A decimeter-level accuracy is expected to be achieved using a single receiver. In this study, the PPP-B2b service is experimentally analyzed based on 7 days of corrections and compared with the RTS provided by the Centre National d Etudes Spatiales (CNES). The availability and completeness of these two RTS products are first evaluated based on the quality of the observation-specific bias (OSB), the satellite orbit and clock offset products. The signal-in-space ranging error (SISRE) is also calculated and evaluated. PPP-B2b can provide stable service in Asia and has better availability and completeness for BDS-3 than does CNES, though the opposite is true for GPS. The analysis reveals a nonnegligible constant satellite-specific bias in the PPP-B2b clock offset for GPS and a smaller bias for BDS-3; this bias is absent in the CNES products. The SISREs of the PPP-B2b products are affected by this bias, but the SISRE STD is comparable to that of the CNES products. Positioning experiments are carried out for the PPP-B2b and CNES products using six stations evenly distributed across China. The kinematic PPP results of BDS-3-only positioning, achieving accuracy at the centimeter level using PPP-B2b, are in good agreement with the GPS-only results using CNES. The abnormal average convergence time exceeding 60 min for GPS confirms that the satellite-specific bias in the PPP-B2b clock offset degrades the pseudorange accuracy, which should be improved in the near future.