灰色模型修正及其在实时GPS卫星钟差预报中的应用研究

An Improved Grey Model for the Prediction of Real-Time GPS Satellite Clock Bias

在GPS实时精密单点定位中,卫星钟差的实时可靠预报是实现GPS实时高精度单点定位的关键之一.星载GPS原子钟频率高,非常敏感,极易受到外界及其本身因素的影响,从而很难掌握其复杂细致的变化规律,这些属性符合灰色系统理论的特点.因此,考虑将钟差的变化过程看作一个灰色系统.在探讨二次多项式和灰色模型卫星钟差预报局限性基础上,提出了利用改进的灰色模型实时预报GPS卫星钟差的研究,最后利用3个不同时段的GPS卫星钟差资料进行不同采样间隔钟差预报精度分析、灰色模型指数系数与预报精度的关系、与二次多项式预报精度比较分析,总结不同卫星钟差类型与模型指数系数的一般关系,并与IGS最终钟差星历产品比较,验证本文提出的改进预报模型的可行性和有效性.为实时GPS动态精密单点定位提供较高精度的卫星钟差产品.

In real-time GPS precise point positioning(PPP),real-time and relia- ble satellite clock bias(SCB)prediction is a key to implement real-time GPS PPP.It is difficult to hold the nuisance and inenarrable performance of space-borne GPS satellite atomic clock because of its high-frequency,sensitivity and impressionable,it accords with the property of grey model(GM)theory,i.e.we can look on the variable process of SCB as grey system.Firstly,based on limits of quadratic polynomial(QP)and tradi- tional GM to predict SCB,a modified GM(1,1)is put forward to predict GPS SCB in this paper;and then,taking GPS SCB data for example,we analyzed clock bias predic- tion with different sample interval,the relationship between GM exponent and predic- tion accuracy,precision comparison of GM to QP,and concluded the general rule of dif- ferent type SCB and GM exponent;finally,to test the reliability and validation of the modified GM what we put forward,taking IGS clock bias ephemeris product as refer- ence,we analyzed the prediction precision with the modified GM,It is shown that the modified GM is reliable and validation to predict GPS SCB and can offer high precise SCB prediction for real-time GPS PPP.