Performance evaluation of BDS-3 PPP-B2b precise point positioning service

A new precise point positioning (PPP) service has been provided by BeiDou global navigation satellite system (BDS-3). The correction parameters, including precision orbit correction, clock offset correction and differential code bias, are transmitted by PPP-B2b signal from BDS-3 geosynchronous orbit satellites. This research conducts a comprehensive evaluation of the accuracy, availability, matching characteristics of PPP-B2b corrections and real-time PPP performance for BDS-3. It is found that PPP-B2b corrections can significantly improve the discontinuous orbit and clock errors caused by broadcast ephemeris updating. The PPP-B2b real-time orbit has slightly better accuracy than the broadcast orbit, and its RMS errors are 6.8 cm, 33.4 cm and 36.6 cm in the radial, along-track and cross-track components for the medium earth orbit (MEO) satellites. However, the accuracy of real-time orbit of the inclined geostationary orbit satellites is about two times poor than that of the MEO satellites. The PPP-B2b real-time clock offset achieves an accuracy of 0.2 ns, improved by about 85.1% compared to the broadcast clock offset. Restricted by the regional tracking network, the accuracies of the PPP-B2b real-time orbit and clock offset are slightly poor than those of the Centre National d’Études Spatiales RT products. The availability of PPP-B2b correction in China is better than 80%, and at least 7 visible satellites with available PPP-B2b corrections can be guaranteed. It should be noted that there exists a temporary mismatching state between the orbit and clock offset corrections each time when the Issue of Data for Correction parameter changes. Test results show that an accuracy of 11 cm in horizontal and 17 cm in vertical after convergence can be achieved by BDS-3 dual-frequency real-time kinematic PPP, and the B1C/B2a ionospheric-free (IF) combination shows better positioning accuracy than the B1I/B3I IF combination. The real-time kinematic PPP employing B1C/B2a IF combination can converge to 27.8 cm in horizontal and 36 cm in vertical in 30 min, while the B1I/B3I combination achieves 42.8 cm and 53 cm in the two components at the same positioning time, respectively.