电离层约束的BDS单频精密单点定位研究

Research on BDS Single-Frequency Precise Point Positioning with Ionosphere Constraint

单频精密单点定位无法通过不同频率观测值的线性组合来消除电离层误差,如何处理电离层误差成为单频精密单点定位(precise point positioning,PPP)的难点。本文将IGS(International GNSS Service)GIM(global ionosphere map)产品作为虚拟电离层观测量,建立电离层约束的单频PPP模型;虚拟电离层观测量的先验方差分别采用常数约束、时空约束和逐步松弛约束3种方法确定。通过4个IGS站连续10 d的BDS数据,对标准PPP和3种不同先验方差的电离层约束PPP进行单频PPP的对比实验。结果表明,常数约束和时空约束的PPP定位精度低于标准PPP,而逐步松弛约束的PPP定位精度与标准PPP相当;电离层约束PPP收敛性能明显优于标准PPP,4个测站收敛时间平均减少了16.2%。

The ionosphere errors can’t be eliminated through the linear combination of different frequency observations in single-frequency precise point positioning.The ionosphere error is a difficulty in single-frequency PPP.In this study,the single-frequency PPP model with ionosphere constraint is established in which IGS GIM products are used as virtual ionospheric observations.The prior variances of virtual ionospheric observations are determined by three methods:constant constraint,space-time constraint and step-by-step relaxation constraint.Based on 10-days BDS data from 4 IGS stations,a single-frequency PPP comparison experiment was conducted for standard PPP and three ionosphere-constrained PPP with different prior variances.The results show that(1)the positioning accuracy of PPP with constant constraint and time-space constraint is lower than that of standard PPP,while that of PPP with step-by-step relaxation constraint is almost equivalent to that of standard PPP;(2)the convergence performance of PPP with ionosphere constraint is better than that of standard PPP,and the convergence time is reduced by 16.2%on average.