| With improvement of service capability of BeiDou Navigation Satellite System,BeiDou application promotion has made great progress.Users are increasingly demanding the precision positioning performance of BeiDou.In recent years,scholars focus on a systematic error in the BeiDou pseudorange observations.This error estimated by observation data of different stations and different receiver types shows consistency to the same satellite,which associated with satellite elevation and frequency,people named it the satellite-induced pseudorange multipath bias.Nowadays,research on the methods to correct this bias is not completely.Further research should be done to improve positioning accuracy and reliability of BeiDou system.Focus on the above problems,this paper aimed on eliminating and weakening the satellite-induced pseudorange multipath bias of BeiDou system,analyzed and discussed the generation mechanism and error characteristics of the bias,proposed an advanced method to extract the bias,and established the error correction model,analyzed the effectiveness of the correction model by a variety of experiments.The main contents of this paper are as follows:(1)The variation trend of the BeiDou MW combination sequence is studied.The mechanism of the satellite-induced pseudorange multipath bias is analyzed.The calculation method of multipath combination is introduced.Then the multipath error variation characteristics of the BeiDou satellite are analyzed and compared with.other navigation satellite systems.The difference between the receiver multipath error and the satellite-induced pseudorange multipath bias is clarified.(2)The multipath combination sequence which can reflect the multipath deviation of the satellite-induced pseudorange multipath bias is calculated.The experiment shows that it has systematic deviation characteristics.By analyzing the influence of satellite type,signal frequency,station location,satellite elevation,observation time and other factors on this systematic deviation,it shows that it has a greater correlation with the elevation and signal frequency,which lays the foundation for the next step of modeling.(3)The improved method for the satellite-induced pseudorange multipath bias is proposed.The global continuous piecewise polynomial fitting formula is derived and the satellite-induced pseudorange multipath bias correction model is established.The effectiveness of the proposed correction model is verified by multiple sets data.The results show that the system deviation in multipath combination sequence and MW sequence can be basically eliminated after the correction of the satellite-induced pseudorange multipath bias.In single frequency precise point positioning,the improvement effect of this model is better than that of the Wanninger Beer model. |
