中低纬地区混合LEO星座增强GNSS UPPP收敛性能评估

针对全球卫星导航系统（GNSS）精密单点定位（PPP）收敛时间过长的问题，提出了利用低轨卫星（LEO）几何结构变化快的优势，增强GNSS非差非组合PPP（UPPP）的收敛性能。选取中低纬度地区28个能接收GPS、GALILEO和BDS3信号的测站观测数据，比较了极轨和混合LEO星座的增强效果。结果表明：混合LEO星座增强GPS、GALILEO和BDS组合系统时，各测站收敛时间减少60%~80%，70%的测站收敛速度优于极轨星座。当混合LEO星座增强单BDS时，CL和GCL组合系统的收敛时间相当，ENU方向定位误差变化基本一致。收敛时间从10~20 min 下降至3 min以内，原因是混合LEO增强BDS定位时，大大改善了卫星的空间结构。

Hybrid LEO constellation augmented GNSS UPPP convergence performance evaluation in middle and low latitudes

To solve the problem of long convergence time of the global navigation satellite system(GNSS) precise point positioning (PPP), we augment the convergence performance of GNSS undifferenced and uncombined PPP(UPPP) by taking advantage of the fast geometry change of low Earth orbit(LEO). Observations from 28 stations capable of receiving GPS, GALILEO and BDS3 signals in middle and low latitudes are selected and the augmented effects of polar orbit and hybrid LEO constellations are compared. The results show that when GPS, GALILEO and BDS are augmented with the hybrid LEO constellation, the convergence time of each station is reduced by 60%~80%, and 70% of the stations converge faster than the polar orbit constellation. And when the hybrid LEO constellation augments the BDS, the convergence time of CL and GCL is identical, and so are their changes of positioning errors in the ENU direction. The convergence time decreases from 10~20 min to 3 min due to the faster change of the hybrid LEO constellation geometry, which improves the satellite spatial structure of BDS.