基于位置观测的北斗广播星历速度精度分析

利用广播星历计算导航卫星的速度向量是GNSS高精度实时测速的必要条件.本文分析了仅以卫星位置向量为观测量的北斗广播星历的速度计算精度.从广播星历拟合过程出发，推导了北斗18参数模型的速度向量计算公式.基于北斗13颗在轨卫星一年的实际轨道数据，分析了全年广播星历计算卫星速度向量的精度.结果表明，利用18参数模型计算的速度误差最大在10-4m·-1量级；在相同拟合时段条件下，地球静止轨道（GEO）和倾斜地球同步轨道（IGSO）卫星的速度精度相当，高于中圆地球轨道（MEO）卫星.通过对位置残差序列分析，得出位置残差误差较小且变化趋势平稳是广播星历计算速度精度较高的原因.分析和计算结果验证了仅用位置观测量拟合北斗广播星历算法的有效性. 

Accuracy Analysis of Satellites Velocity with BDS Broadcast Ephemeris Based on Position Observationsormalsize

Using broadcast ephemeris to calculate the velocity vector of navigation satellites is a necessary condition for GNSS real-time velocity determination. In this paper, the accuracy of velocity vector calculated by Beidou broadcasting ephemeris only with position observations is analyzed, and the calculation formula of velocity vector with Beidou 18-element model is deduced. Based on one year data of 13 Beidou satellites in orbit, the accuracy of velocity vector calculated by broadcasting ephemeris is obtained. The results show that the maximal velocity error calculated by the 18-element model is in the order of 10-4m·-1. At the same fitting period, the velocity accuracy of GEO and IGSO satellites is higher than that of MEO. By analyzing position residual sequence, the conclusion is drawn that the velocity accuracy computed by broadcast ephemeris is very high because of little position residual with smooth change trend. The analysis and calculation results in this paper verify the effectiveness of fitting BDS broadcast ephemeris only using position observations.