Authors:Min Li Tianhe Xu Meiqian Guan Fan Gao Nan Jiang

来源出版物：GPS Solutions DOIhttps://doi.org/10.1007/s10291-021-01217-9出版年：December 2021

Abstract:GNSS signals are blocked in forests, urban canyons, and indoors. Precise positioning can hardly be guaranteed in these challenging environments. A low earth orbit (LEO) constellation serving as a navigation system can provide stronger signal power to ground receivers due to its shorter transmission path than GNSS. The fast motion of LEO satellites contributes to the fast change of spatial geometry, allowing for rapid convergence of precise point positioning (PPP), and is efective in detecting carrier phase cycle slips. This study comprehensively analyzed the LEO-constellation-augmented multi-GNSS for real-time PPP in various challenging environments, including the blocking of satellite signals, cycle slips, the two issues occurring simultaneously, and signifcant multipath efects. An improved cycle slip detection and fxing algorithm taking advantage of LEO satellites is proposed. The GPS, BDS, and a 96-satellite polar-orbiting LEO constellation are designed, and observations at a mid-latitude station are simulated. The results show that the inclusion of LEO satellites shortens the convergence time and signifcantly improves the cycle slip fxing performance of multi-GNSS PPP. Three to four visible LEO satellites can shorten the GPS/BDS/LEO (GCL, C is the designation used in RINEX for BDS) PPP convergence time to 4 min compared to 20 min for the GPS/BDS (GC) solutions. Additionally, the correct cycle slip fxing time shortens from 3.3 min for the GC solution to 0.8 min for the GCL solution. When LEO satellites are free of cycle slips, the GNSS integer cycle ambiguities can be instantaneously fxed, and PPP instantaneous re-convergence is obtained. When signifcant multipath efects are considered, the time for GNSS/LEO frst correct fxing is 3 min longer. The PPP solutions are noisier because the relatively shorter continuous observation time of LEO satellites is not benefcial for the smooth of multipath errors. In the case of GNSS and LEO satellites under both signal shielding and cycle slips, the GNSS/LEO PPP re-convergence and cycle slip fxing both degrade when the cut-of elevation increases from 20° to 40°, since LEO satellites are almost out of sight at a cut-of elevation of 40°. It is concluded that the inclusion of LEO satellites considerably improves the GNSS PPP in terms of the (re-)convergence and cycle slip fxing performance.

Keywords:Low earth orbit · Signal shielding · Cycle slips · Multipath · Precise point positioning · Real-time

Citations：Li, M., Xu, T., Guan, M.et al.LEO-constellation-augmented multi-GNSS real-time PPP for rapid re-convergence in harsh environments.GPS Solut26,29 (2022).