The Research On BDS Multipath Error

In recent years,Beidou satellite navigation and positioning system(BDS),which designed and developed by China independently,has been rapid development,and has owned the ability to provide users in the Asia-Pacific region with real-time high-precision positioning,navigation,timing services.With the continuous improvement of BDS system and the deepening of research,BDS already has the ability of high-precision positioning,and has been successfully applied to high-precision deformation monitoring.In the deformation monitoring of complex environment such as large buildings,bridges and dams,the BDS positioning results are susceptible to various errors.Usually,the tropospheric error,the ionospheric error,the receiver Clock error can been eliminated by double differenceing the observations between the stations and the inter-satellite.And the multi-path error formed by the signal interference caused by the station environment becomes an important error source that affects the positioning results.So how to weaken the impact of the error on the positioning results,becomes as an important issue which can not be ignored in BDS high-precision deformation monitoring.In this paper,a multipath error mathematical model,characteristic of BDS multipath error,filtering method,multipath error modeling and corrective measures are studied in this paper.The main work and achievements of this paper can be summarized as follows:1?The mathematical model of multipath error is studied,and the characteristics of cycle and frequency of multipath error are analyzed.The factors influencing the size of the multipath error are studied emphatically,and the reflection coefficient,the horizontal distance of the reflector to the receiver antenna and the incident angle of the reflected signal are given in detail,and the influence of the multi-path error is given.2?To obtain the characteristics of BDS multipath error,this paper summarizes the orbital characteristics of BDS satellite with different constellations,by observing the measured data,it is found that different constellations have different orbital repetitive periods,such as GEO and IGSO satellites.whose orbital repetition period are about 1 sidereal day,and the MEO's orbital repetition period are about 7 sidereal days.And the orbital repetition periods corresponding to each satellite have different time advances at different times.The single difference residual method is introduced in this paper.By analyzing the correlation between the single residuals of the carrier phase observations of each satellite in the adjacent two days,it is found that the position of the maximum value of the mutual correlation coefficient is corresponding to the time advances of the satellite orbital repetition period.It is verified that the multipath error is extracted and corrected by using the single-residual residual based on the carrier phase observations.3?This paper introduces the filtering method commonly used in multipath error modeling.The optimal wavelet basis function and the method of determining the optimal decomposition layers are summarized with the analog signal.The sym6 wavelet and the optimal decomposition layer are determined.And compared the filtering performance with EMD.Finally,the two methods are used to measure and correct the multipath error of BDS data.And verify the superiority of sym6 in reduce the BDS multipath error and improve the accuracy of positioning results.