Real-time multi-frequency phase OSB estimation from BDS-3 PPP-B2b and Galileo HAS

Abstract To address the long convergence time of satellite-based Precise Point Positioning (PPP) using BDS-3 PPP-B2b and Galileo high accuracy service (HAS) in the Asia-Pacific region, this study investigates real-time multi-frequency phase OSB estimation and PPP-AR based on the integration of the two services. In the Asia-Pacific region, real-time orbit and clock corrections from PPP-B2b and Galileo HAS were first recovered and unified in reference. A tightly combined real-time phase OSB estimation method was then developed using observations from the complementary constellations, and a corresponding tightly combined real-time PPP-AR model was established. Four schemes were designed: PPP-B2b BDS-3/GPS, HAS Galileo/GPS, PPP-B2b BDS-3/GPS + HAS Galileo, and HAS Galileo/GPS + PPP-B2b BDS-3. Phase OSB products were estimated and ambiguities were fixed using 10 d of multi-frequency global navigation satellite system observations from 21 reference stations in the Asia-Pacific region. PPP/PPP-AR performance was validated using observations from 11 rover stations, and the influence of GPS precise ephemerides with different accuracies on phase OSB estimation was also analyzed. The results show that the integrated PPP-B2b/Galileo HAS schemes provided better satellite geometry than the single-service schemes. Among the tested schemes, B2b C/G + HAS E achieved the best positioning performance, with mean E, N, and U accuracies of 4.7 cm, 2.9 cm, and 7.6 cm, respectively, for the PPP-AR fixed solution, and a mean convergence time of 5.65 min. Compared with the float solution, the improvements were 27.7%, 17.1%, 16.5%, and 42.0%, respectively. In the Asia-Pacific region, HAS GPS showed data interruptions and a smaller number of visible satellites, which resulted in lower phase OSB sequence stability and PPP/PPP-AR positioning accuracy than PPP-B2b GPS. This explains the better performance of B2b C/G + HAS E than HAS E/G + B2b C. The proposed satellite-based PPP integration scheme uses satellite-broadcast corrections at the user end and does not require real-time correction transmission through terrestrial communication networks, providing a technical option for real-time high-precision positioning in areas with limited network access in the Asia-Pacific region.