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

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.