三频电离层延迟改正中多路径误差和观测噪声的削弱算法

多频测距系统可以借助多频观测数据削弱电离层延迟的影响,但多频改正算法在改正电离层延迟项的同时会不同程度地放大多路径误差、观测噪声等伪距误差的影响。其中利用三频数据可以将电离层延迟改正至二阶项,也可以只改正至一阶项,分别称为三频二阶改正和三频一阶改正。首次推导了利用三频观测数据削弱伪距中多路径效应和观测噪声等误差的算法,使三频电离层延迟改正中伪距误差的影响大大减小。通过对三频实测数据的处理和分析验证了算法的有效性并给出了一些有益的结论和建议:在利用三频观测数据进行电离层改正时,首先改正伪距中的多路径误差和观测噪声,然后采用三频二阶改正算法将电离层延迟改正至二阶项,将有效提高伪距改正精度。如果不能有效削弱这些误差的影响,宜采用三频一阶改正或双频改正。

An Algorithm of Multipath Error and Observation Noise Weakening in Triple-frequency Ionospheric Delay Correction

The ionospheric delay can be weakened by multi-frequency observations,but pseudorange errors such as multipath errors and observation noises are magnified to different degrees due to using multi-frequency methods.Hereinto,by triple-frequency observations the ionospheric delay can be corrected to the second order or only the first order,which are named triple-frequency of one order correction and triple-frequency of two order correction respectively.The algorithm of weakening the multipath errors and observation noises using triple-frequency observations is provided in this paper,which greatly decreases the effects of pseudorange errors in calculating the triple-frequency ionospheric delay correction.By processing triple-frequency experimental observations,the algorithm is validated and some useful conclusions and advises are summarized: to correct the ionospheric delay using triple-frequency observations,firstly the multipath errors and observation noises should be weakened from the pseudoranges,and then the ionospheric delay is corrected.In this way the precision of corrected pseudorange will be improved.If the errors can't be weakened efficiently,the algorithm of triple-frequency of one order correction or dual-frequency correction is more suitable.