导航卫星历书拟合初值的选取与误差分析

Improvement on Initial Values Selection and Errors Analysis of Almanac Fitting of Navigation Satellites

研究了GPS历书拟合算法,针对常用算法拟合精度受初值影响较大,且迭代计算一般不能收敛于最小拟合误差的情况,提出了称为"二步法"的改进历书拟合算法。即首先进行短弧拟合,并将拟合结果作为长弧拟合的初值使用;取计算过程中的最小拟合误差对应值代替最终收敛值作为拟合结果。经多组GPS实际轨道拟合试验,结果表明"二步法"拟合精度一般能提高约50%。

Based on the study about the GPS almanac parameters fitting arithmetic, an improved method, so called ＂two step arithmetic＂, was introduced in this article for that instability fitting accuracy affected by the initial values and the non-least convergence errors through iterative calculations. It meant that a short arc orbit almanac should be firstly fitted, and the result wouldl be used as the initial value for the formal almanac fitting of the whole arc orbit. The almanac corresponding to the least error during iterating calculations should be selected as the final result, in the stead of the convergence one. The results from many examples on IGS GPS satellite orbits showed that the fitting position errors adopting the ＂two step arithmetic＂ were generally decreased by 50%.