GPS长距离和多测段定位中广播星历的改进方法

IMPROVEMENT OF GPS BROADCAST EPHEMERIDES USED FOR LONG BASELINE AND MULTI SESSION RELATIVE POSITIONING

本文分析了广播星历误差对ＧＰＳ长基线和多测段定位结果的影响，由此提出了旨在减弱卫星轨道误差对于相对定位精度影响的一种简便而又实用的方法，即先按卫星运动的力学模型建立状态方程，其初始状态向量由某组广播星历得出，由每组广播星历建立观测方程。由数值积分得出的参考轨道经由广播星历ｔｏｅ时刻的位置和速度观测值的最小二乘平差所得的改正后的轨道，不仅可消除各组广播星历间的不一致性，而且其精度也高于任何一组广播星历。利用所研制的软件对３个测段跨度约１０００ｋｍＧＰＳ网实测数据的计算结果表明，利用本文提出的方法得到的星历精度高于广播星历，而且是一种连续的轨道。

In this paper, the influences of error in GPS broadcast ephemerides on long baseline and multi session relative positioning are analyzed. One practical method is given to weaken these influences. The reference orbits are obtained by numerical integrating the satellite motion equations, while their initial conditions can be calculated from any group of broadcast ephemerides. The satellite state equations can be established according to their dynamical model. The observation equations are established with every groups of broadcast ephemerides. After least square estimating the improved orbits are got, and the inconsistency between broadcast ephemeris is no longer existed. The accuracy of refined orbits will be higher than any groups of broadcast ephemerides. With developed software, the processing results of a 3 session large network show that the orbits calculated with the method mentioned in this paper will be more precise than broadcast ephemerides, and accuracy of 10 -8 level in long baseline relative positioning can be desired.