GNSS观测值统一表达及组合PPP解算性能分析

针对GNSS多系统组合进行PPP定位的问题,推导了GNSS观测值统一表达式;进而给出了基于UofC模型的多系统组合PPP的函数模型和随机模型;最后采用6个IGS观测站24 h观测数据对7种组合模型的PPP进行解算,并从收敛率、收敛速度和定位精度等方面进行了统计分析。实验结果表明,当观测时长为60 min时,GPS/GLONASS/BDS组合PPP收敛性能最好,收敛率为91.7%,平均收敛时间为16.1 min;而BDS PPP收敛性能最差,收敛率仅为32.7%,平均收敛时间为38.4 min。可见,多系统组合有利于提高精密单点定位的解算性能。对于定位精度,在观测时长较短时(如0.5 h),GPS/GLONASS/BDS组合PPP整体上具有最优的定位精度,(N,E)方向偏差和标准差分别为(0.3,0.5)cm和(1.9,4.3)cm;短时间内对流层参数与垂直方向的强相关性,将致使U方向精度较差。

Uniform Expression of Multi-GNSS Observation and Performance Analysis of the Combined Precise Point Positioning

In order to evaluate the performance of multi-GNSS precise point positioning,the uniform expression of multi-GNSS observation is first derived.Then,the UofC function and stochastic models are introduced.Finally,the static solutions of seven different PPP models are obtained based on the observations from 6 IGS tracking stations.The statistical results show that the GPS/GLONASS/BDS PPP has a best convergence percentage when the observation duration is short.For the 1 h-duration observation data sets,the convergence percentage and mean convergence time of GPS/GLONASS/BDS PPP are 91.7% and 16.1 min,respectively.While the convergence percentage and mean convergence times of BDS PPP are 32.7% and 38.4 min,which is the worst.Moreover,the position biases and standard deviations for the GPS/GLONASS/BDS PPP are both better than (0.3,0.5) cm and (1.9,4.3) cm respectively in north and east direction,and the accuracy in the up direction is low because of the strong correlation between the up component and the tropospheric delay.