Abstract
To satisfy the demands of civil aviation organizations and other users of satellite navigation systems for high-precision and high-integrity service performance, many countries and regions have established satellite-based augmentation systems (SBAS) referring to the Radio Technical Commission for Aeronautics (RTCA) service standards and agreements. The BeiDou SBAS (BDSBAS) provides both single-frequency service, which augments Global Positioning System (GPS) L1 C/A signal, and dual-frequency multi-constellation (DFMC) service, which augments BeiDou Navigation Satellite System (BDS) B1C and B2a dual frequency signals presently, meeting the requirements of the RTCA DO-229D protocol and the SBAS L5 DFMC protocol requirements, respectively. As one of the main error sources, the pseudorange bias errors of BDSBAS monitoring receivers were estimated and their effect on the performance of the BDSBAS service was analyzed. Based on the user algorithms of SBAS differential corrections and integrity information, the service accuracy, integrity, and availability of the BDSBAS were evaluated using real observation data. The results show that the maximum of monitoring receiver pseudorange bias errors between L1P and L1P/L2P can reach 1.57 m, which become the most important errors affecting the performance of the BDSBAS service. In addition, the results show that the pseudorange bias of GPS BlockIII is the smallest, while that of GPS BlockIIR is the largest. Compared with the positioning accuracy of the open service of the core constellation, the positioning accuracy of the BDSBAS service can be improved by approximately 47% and 36% for the RTCA service and DFMC service, respectively. For RTCA services, the protection limit (PL) calculated with the integrity information can 100% envelop the positioning error (PE) and no integrity risk event is detected. The service availability of BDSBAS for APV-I approach is approximately 98.8%, which is mainly affected by the availability of ionospheric grid corrections in the service marginal area. For DFMC service, the integrity risk is not detected either. The service availability for CAT-I approach is 100%. Improving the availability of ionospheric grid corrections is one of the important factors to improve service performance of BDSBAS RTCA service.
Highlights
BeiDou SBAS (BDSBAS) uses the L1P and L2P dual-frequency pseudorange data of the monitoring receivers to calculate Global Positioning System (GPS) clock differential corrections, and these corrections are used by where PL1CA is the pseudorange of L1CA; differential code biases (DCB) p1c1 is the DCB between L1CA and L1P; GPS L1C/A single-frequency users to correct the satellite clock errors
To weaken the influence of the pseudorange bias on satellite-based augmentation systems (SBAS) correction, the pseudorange where doriclk is the satellite clock correction calculated with GPS L1P/L2P, and the dclk bias difference (α L1P − α L1P/L2P ) between the L1P single-frequency and L1P/L2P dualis the satellite clock correction broadcasted by be RTCAand service, whichfrom has the deducted frequency ionospheric-free combination should estimated corrected the pseudorange bias
Where doriclk is the satellite clock correction calculated with GPS L1P/L2P, and the dclk is the satellite clock correction broadcasted by SBAS Radio Technical Commission for Aeronautics (RTCA) service, which has deducted the pseudorange bias
Summary
When the GNSS continues to expand its application areas, high-end users, such as those in precision agriculture, ports, and civil aviation, have introduced higher standards of use requirements for its positioning accuracy, integrity, and availability [4] In this case, some countries and regions have established satellite-based augmentation systems (SBAS). The error sources that affect the BDSBAS mainly include clock–ephemeris errors, ionospheric delay, tropospheric delay, multipath noise, and the pseudorange bias, and there are already some effective correction methods to eliminate these observation errors. We receive the SBAS product broadcast by GEO satellites through the user receiver, and we evaluate and analyze the user’s positioning performance, availability, continuity, and integrity.
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