Abstract: To mitigate the issue of poor accuracy during the convergence phase of precise point positioning (PPP),we investigates the improvement of positioning accuracy using the RTS (Rauch-Tung-Striebel) backward smoothing algorithm. The evaluation of static PPP using the forward Kalman filter indicates that BDS can achieve an accuracy of 2.6mm,2.0mm,7.8mm in N、E、U direction. The GPS+Galileo combined PPP can achieve the best accuracy,which is 1.7mm,2.1mm,3.4mm in the N、E、U direction. The kinematic PPP using the RTS smoothing method indicate that an accuracy of 3.3mm,3.4mm,9.0mm can be achieved for the BDS PPP in the N、E、U direction. Introducing the GPS,GLONASS,or Galileo observations can improve the accuracy of BDS PPP by more than 50%. The analysis of on-vehicle dynamic testing further indicates that utilizing the reverse RTS smoothing algorithm for PPP calculations can achieve positioning accuracies of 0.028meters in the north direction (N),0.015 meters in the east direction (E),and 0.033 meters in the up direction (U).

Key words: BDS, precise point positioning, Kalman filtering, RTS backward smoothing