Estimating the orbit error of BeiDou GEO satellites to improve the performance of multi-GNSS PPP ambiguity resolution

摘要

The Chinese BeiDou Navigation Satellite System (BDS) contains five geostationary earth orbit (GEO) satellites, which maintain almost stationary with respect to the earth. The accuracy of GEO orbit is very poor, which has negatively influenced multi-GNSS precise point positioning (PPP) integer ambiguity resolution (IAR). To overcome this problem, we estimate GEO orbit error corrections together with the narrow-lane fractional cycle bias (FCB), which is used to refine the orbit. We also estimate systematic bias in current GLONASS and BDS precise satellite clock products. Then, this solution is validated with combined GPS, GLONASS, and BDS PPP-IAR. A 7-day dataset of 45 stations was used in the experiment. It is demonstrated that, after considering GEO satellite orbit errors, the narrow-lane FCB estimates have comparable quality for each system. For kinematic PPP with an observation time of 6 min, only 14.7% of cases could be fixed by GPS alone, whereas the percentage decreased to 7.5% for GPS + GLONASS + BDS without considering GEO orbit errors. In contrast, if we consider that error, the percentage for GPS + GLONASS + BDS improved substantially to 96.9%.