伪距测量中的时标偏差影响分析

Analysis of influence of timescale deviation upon pseudorange measurement

伪距是卫星导航系统的基本观测量,是实现导航定位、精密定轨和精确授时的基础。基于伪距、钟差和时标偏差的概念与定义,讨论了时标偏差对卫星伪距测量的影响特性;在此基础上,给出了利用伪距O-C(观测值与计算值之差)进行时标偏差解算的计算模型;理论分析表明:时标偏差影响主要体现在伪距变率项;对于MEO卫星,时标偏差影响不仅会使真实的O-C曲线斜率变大、曲线变长,而且会使多个弧段O-C曲线呈现锯齿状,表现为每个弧段解算的参数不能用于跨弧段预报。最后,利用北斗试验系统MEO卫星实测数据进行了验证分析,试验结果表明:采用实测数据计算的时标偏差精度约在0.02s左右,不同弧段解算结果比较稳定,并且扣除时标偏差后的O-C计算结果也与理论结果具有较好的一致性,从而验证了本文时标偏差理论分析和计算模型的正确性。

The pseudorange is a basic observation in a satellite navigation system,and is the foundation of navigation and positioning,precise orbit determination and precise time transfer.According to the concepts and definitions of pseudorange,clock offset and timescale deviation,the influence of timescale deviation on the pseudorange measurement is discussed.By using the O-C（the difference between measured value and computed value） results of pseudorange measurements,a model for calculating timescale deviation is given.The academic analysis indicates that the influence of timescale deviation is mainly laid on the pseudorange changing rate.If the timescale deviation exists in the MEO satellite pseudorange measurements,the O-C curve will become longer,the slope of O-C curve will become larger,and the O-C curves of different observing arcs will become indention.As a result,the prediction parameters which are calculated with one observing arc will be wrong and can′t be used to other observing arcs.Finally,an experimental analysis is performed with the MEO satellite actual observing data of the compass navigation system.The results show that： 1） the accuracy of calculated timescale deviation is about 0.02 s;2） the timescale deviations for different observing arcs are stable;3） the O-C results with the timescale deviation removed are accordant with the theory results;4） the correctness of the academic analysis and computational model is validated.