Research On Methods Of BDS Carrier Phase Multipath Error Processing

GNSS high-precision positioning is affected by a series of errors,one of the significant errors is Multipath error.In the case of short baseline,the ionospheric delay error and tropospheric delay error over the two stations at the two ends of the baseline have strong correlation.The differential technique can eliminate the effects of receiver clock error and satellite clock error,while the ionospheric delay error and tropospheric delay error are also greatly weakened.However,the carry phase multipath error is mostly determined by the environments around the station,but the environment around the station at the two ends of the same baseline is different,it is difficult to eliminate the influence of multipath error by relative positioning technology.BeiDou Navigation Satellite System(BDS)already has the capability to realize global positioning,push BDS applying in high-precision positioning is an inevitable research trend.Therefore,this paper mainly studies the multipath error processing in BDS carrier phase observation.The main contents are as follows:(1)Analyze the causes of multipath error in carrier phase observation,and deduce the multipath error function model when the reflecting surface are horizontal and vertical.In particularly,we discuss the magnitude of the carrier phase multipath error and its spatiotemporal environment characteristics,discuss how the reflection coefficient,distance,etc.affect it by experiments(2)The BDS satellite repetition period is studied from the two aspects of aspects repetition period and orbit repetition period.The GEO satellites are analyzed from the perspective of single-difference observations to verify its periodic characteristics.The multipath error model is extracted from the single-difference observation domain.By using different weighting strategies extracting single difference residual solution,experiment shows that single difference residual is not sensitive to different weighting strategies;the maximum correlation coefficient method is used to verify the periodic repeating characteristics of satellite multipath error.The BDS GEO/IGSO satellite multipath error repetition period is about one day.The second day's multipath error sequence will have a 236 seconds advancement than the first day's multipath error sequence.The MEO satellite multipath error repetition period is about in 7 days,it also repeated with an advance amount,and its value is around 1700 seconds.The difference between the multi-path error repeat period advance value and the satellite orbit repeat period advance value varies from several seconds to several tens of seconds.(3)A multi-path error correction method in BeiDou carrier phase observation range combined with Vondrak filter and modified sidereal filtering algorithm is proposed,which is compared with the multi-path error correction method of the observation range combined with wavelet filtering and modified sidereal filtering algorithm.The experimental results show that the wavelet and Vondrak filtering methods can effectively filter the random noise and extract the accurate repetitive multipath error model.After applying modified sidereal filtering algorithm to the BDS single-difference observation domain and correcting the multipath error,the positioning accuracy has significant improved.The Vondrak filter modeling method is slightly better than the wavelet method.