Abstract
Abstract: In this contribution, the processing strategies of real-time BeiDou System (BDS) precise orbits, clocks, and ionospheric corrections in the National BDS Augmentation Service System (NBASS) are briefly introduced. The Root Mean Square (RMS) of BDS predicted orbits are better than 10 cm in radial and cross-track components, and the accuracy of the BDS real-time clock is better than 0.5 ns for Inclined Geosynchronous Orbit (IGSO) and Mid Earth Orbit (MEO) satellites. The accuracy of BDS Geostationary Earth Orbit (GEO) orbits and clocks are worse than the IGSO and MEO satellites due to its poor geometry conditions. The real-time ionospheric correction is evaluated by cross-validation, and the average accuracy in the vertical direction is about 4 TECU. With these real-time corrections, the overall single and dual-frequency kinematic precise point positioning (PPP) performance in China are evaluated in terms of positioning accuracy at the 95% confidence level and convergence time. The BDS PPP positioning accuracy shows significant regional characteristics due to the geometry distribution of BDS satellites and the accuracy of ionospheric model in different regions. The BDS dual-frequency PPP positioning accuracy in high-latitude and western fringe region is about 0.5 m and 1.0 m in the horizontal and vertical component, respectively, while the horizontal accuracy is better than 0.2 m and the vertical accuracy is better than 0.3 m in the midlands. The convergence time of the BDS PPP is much longer than the GPS PPP and it needs more than 60 min to achieve the accuracy better than 10 cm in both horizontal and vertical directions for dual-frequency PPP. Similar with dual-frequency PPP, the positioning accuracy of the BDS single-frequency PPP in the fringe region is worse than other regions. The positioning in the midlands can achieve 0.5 m in horizontal component and 1.0 m in the vertical component. In addition, when GPS and BDS are combined, the positioning performance of both single-frequency and dual-frequency PPP can be greatly improved.
Highlights
In order to provide real-time precise positions which are demanded by many time-critical applications, such as geohazard early warning, the International GNSS service (IGS) [1] established aReal-Time Working Group (RTWG) in 2001 with the goal of providing real-time service (RTS)
EUREF reference stations, Abdelazeem et al develop a real-time regional ionospheric model (RT-RIM) over Europe, it was proved that the precise point positioning (PPP) performance by the RT-RIM in mid-latitude can be improved about 40% in comparison with the IGS global ionosphere maps (GIMs) [18]
It is noted that the accuracy of C07 and C10 is worse than other Inclined Geosynchronous Orbit (IGSO) in each direction, which is caused by the inaccurate solar radiation pressure (SRP) and the switch model for the yaw-attitude and the normal-attitude in eclipsing seasons
Summary
In order to provide real-time precise positions which are demanded by many time-critical applications, such as geohazard early warning, the International GNSS service (IGS) [1] established a. In order to reduce the positioning error caused by ionospheric delay, GNSS systems, such as GPS, BDS, and Galileo, provide ionospheric models via satellite broadcast messages, i.e., the Klobuchar and the NeQuick model [13,14,15]. By processing GPS observations from 60 IGS and EUREF reference stations, Abdelazeem et al develop a real-time regional ionospheric model (RT-RIM) over Europe, it was proved that the PPP performance by the RT-RIM in mid-latitude can be improved about 40% in comparison with the IGS GIM [18]. By using these real-time streams, Centre National d’Études Spatiales (CNES) provides publicly available real-time corrections for all the GNSS, including BDS.
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