A Simplified BDS Broadcast Ephemeris and State Space Representative (SSR) Matching Method for BDS-Only Real-Time Precise Point Positioning (PPP)

Abstract

As opposed to the GPS real-time precise point positioning (PPP) with sophisticated orbit/clock recovery method, BDS real-time PPP applications were limited by the fact that no internationally recognized BDS issue of data (IOD) calculation and matching method was defined. This paper proposes a simplified BDS broadcast ephemeris and state space representative (SSR) matching method for the BDS precise orbit and clock recovery in real time. Unlike the existing method, the proposed method does not need to perform IOD calculation which involves several bitwise operations. Instead, it only needs to monitor the BDS SSR IOD updating status. Comparison result shows that the proposed method can reduce 6.97% computational time for the 24-hour real-time orbit/clock product recovery. Using the proposed matching method, Centre National d’Études Spatiales (CNES) BDS real-time orbit and clock product from day of year (DOY) 119 to 128 2018 were evaluated. By comparing the 10-day dataset with German Research Centre for Geosciences Potsdam (GFZ) final products, we could see that BDS real-time orbit accuracies were greatly improved, i.e. 1.644-6.143 m real-time precise orbit for Geosynchronous Earth Orbit (GEO) satellites, 0.059-0.286 m for Inclined Geosynchronous Satellite Orbit (IGSO)/Medium Earth Orbit (MEO) satellites. In the meantime, 0.12-2.32 ns real-time clock precision was obtained. Both static and kinematic tests were adopted to evaluate BDS-only real-time PPP using CNES real-time corrections. The results indicated that cm-level horizontal and < 0.1 m vertical precisions were obtained in static experiment. As for the kinematic test, < 0.1 m horizontal and dm-level vertical precisions were obtained in an unmanned aerial vehicle experiment.