基于方差分量估计的不同截止高度角下的组合单点定位

BDS/GPS/GLONASS组合系统定位时,由于系统间卫星测距精度的差异性,需要合理确定卫星间权比,Helmert方差分量估计常被用于确定不同类观测值间权比;而当观测值含有粗差时,Helmert方差分量估计定位结果容易被粗差污染或收敛失真,出现大的偏差。文中基于Helmert方差分量估计,引入等价权因子IGGIII函数,建立抗差Helmert方差分量估计权函数模型,对比分析其在低截止高度角10°、15°和20°下,在BDS/GPS/GLONASS组合系统定位中的应用及定位精度,并讨论分析在高截止高度角30°和40°下,组合系统和单系统BDS的定位精度。实验结果表明:当观测值无明显粗差时,Helmert方差分量估计和抗差分量估计的定位精度相当,略低于高度角权函数的定位结果,点位精度RMS优于2.5m;含粗差时,抗差解定位精度最高;当截止高度角为30°时,BDS单系统定位精度RMS优于5m,而组合系统RMS接近3m;为40°时,组合系统平面精度RMS优于2m,三维精度RMS优于6m,而单系统不能定位。

Combined single point positioning with different cut-off elevation angle using variance component estimation

When the combination of BDS/GPS/GLONASS system is positioned,due to the difference of the accuracy of satellite ranging between systems,a reasonable determination of weight ratio between satellites is needed.Helmert variance component estimation is often used to determine weight ratio of different observations.However,when the observations contain gross errors,the positioning results of Helmert variance component estimation are easy to be contaminated by gross errors or convergence distortion.This paper,based on Helmert variance component estimation,introduces the equivalent weight factor IGGⅢ function,to establish weight function model of robust Helmert variance component estimation,comparing and analyzing its application and positioning accuracy in combined of BDS/GPS/GLONASS system positioning under low cut-off angles of 10°,15°and 20°.Then it discusses and analyzes the combination system and BDS positioning accuracy with the high cut-off elevation angle of 30°and 40°.Experimental results show that:when observations have no significant gross errors,the positioning accuracy of Helmert variance component estimation and robust component is quite similar,and slightly lower than that of elevation angle weigh function,of which the positioning accuracy is better than 2.5 m;while containing outliers,the positioning accuracy of robust solution is the highest;when the cut-off elevation angle is 30°, the positioning accuracy of the BDS single system is better than 5 m,while that of the combination system is nearly 3 m;when is 40°,its horizontal accuracy is better than 2 m,and 3D accuracy is better than 6 m, while the single system can't be positioned.