Research On Mitigating GNSS Multi-path Error By Sidereal Filtering Method Based On Un-difference Error Corrections

With the development of GNSS,the fusion of multi-system and multi-frequency observation data will be the development trend of GNSS precise location service in the future.The phase measurement error due to multipath effect is highly correlated with the station environment,and multipath error can't be eliminated by conventional differential methods,and there is also a lack of effective high-precision mathematical models to describe it,multipath error has always been one of the main error sources affecting GNSS precision data processing.This paper mainly focuses on the problem of weakening the influence of multi-path error in short baseline measurement,and the following work has been done:(1)Theoretical analysis of the mechanism and effect of multipath error.Firstly,the mechanism of multipath error in observation environment is theoretically analyzed and deduced,the influence of multipath error on the amplitude and frequency of carrier signal is further analyzed,the variation of multipath error caused by different material signals and reflecting point distances is simulated.(2)Analyzed and evaluated the orbital repetition period of different constellation satellites in GPS,BDS and GALILEO.Several methods for calculating satellite orbital repetition period are summarized,and some suggestions for improving the above methods are put forward.The characteristics of satellite orbital repetition period of these navigation satellite systems are systematically analyzed through data experiment,it is pointed out that the orbital repetition period jump of BDS GEO and IGSO satellites is related to orbital maneuver.(3)The sidereal filtering method is improved,and sidereal filtering method based on un-differential error corrections is proposed.The traditional sidereal filtering method based on observational domain needs to computing SD residuals from DD residuals.There are some shortcomings in the use of single-difference corrections.To solve these problems,sidereal filtering method based on un-differential error corrections is proposed.The consistency between the un-differential error corrections method and the single-difference corrections is proved theoretically.(4)Sidereal filtering method based on un-differential error corrections is analyzed through experiments.Data experiments were carried out to compare the results of DD residuals,one-hour static positioning and dynamic positioning of the whole day before and after multi-path error correction.Through the above experiments,it is found that after using sidereal filtering method based on un-differential error corrections,the average improvement of DD residuals in the GPS,BDS and GALILEO is about 40%;for static positioning test results,the average improvement rate of XYZ is 60% in high multipath environment and 26% in normal environment;for the results of dynamic positioning test,the average improvement rate of NEU is 45% in high multipath environment and 20% in normal environment.Expected experimental results are achieved,and the validity of sidereal filtering method based on un-differential error corrections is proved.