The Clock Constant Bias in BeiDou PPP-B2b signals: estimation and impact analysis on precise positioning and time transfer

Abstract The performance of precise point positioning (PPP) is closely related to the quality of precise products and can be degraded by the Constant Clock Bias (CCB) present in PPP-B2b corrections. To address this issue, a datum-unified CCB extraction method based on reference station networks is proposed. By incorporating virtual CCB constraints, a full-rank PPP model constrained by CCB is established. Its impact on precise positioning and time transfer was validated using a reference network in the Asia-Pacific region. The results indicate that CCB is a satellite-dependent bias, independent of station distribution, and exhibits high temporal stability with an overall standard deviation better than 0.3 ns. However, significant day-boundary jumps were observed in GPS satellites. After accounting for CCB, both static and kinematic PPP convergence performance is improved, and the distribution of post-fit residuals became more concentrated. In terms of time transfer, the accuracy is improved by approximately 18%–54% across links of different lengths (944 km, 1381 km, 3066 km, and 4438 km), with an overall time transfer accuracy better than 0.3 ns. Furthermore, both short-term and long-term stability of time transfer were enhanced to varying degrees. At averaging times ranging from 960 s to 61 400 s, the stability of all links is improved by an average of 16%–39%, achieving a time transfer stability on the order of 10 −15 .