Research Of Differential BDS Positioning Based On Double-frequency

Beidou Navigation Satellite System(BDS)is one of the Global Navigation Satellite System(GNSS),established and managed by China independently.With the capable navigation service area covering the Asia-Pacific region,BDS can serve a comparable positioning accuracy compared to GPS.In addition,BDS is the first and the only GNSS that has two available civilian signals in use.BDS plays an important role in civil and military affairs and the high accuracy positioning based on BDS has become the research hotspot.The research focus on the BDS high accuracy positioning,involving of the Differential Beidou System(DBDS)and the double-frequency combined positioning.This paper began with a detailed introduction to BDS,including satellite system,coordinate system,time system,signal structure and ranging code characteristics.Decoding of data format RINEX3.02 and data transmission format RTCM10403.2 were also introduced in this part.In the next part,the principle of navigation positioning and errors affecting positioning were analyzed.Several classical error correction models were compared with advantages and disadvantages,from which adopted model is determined.After determining the three steps of positioning,the satellite position was calculated,and the user position was calculated by Iterative Least Square(ILS)algorithm with the pseudorange corrected by the adopted error-off model.In the Differential BDS(DBDS)part,DBDS was introduced involving of several mainstream differential techniques with advantages and disadvantages.Pseudorange DBDS of Single base station technique was adopted to operate the contrast experiment of B1 I and B2 I frequency.Positioning result was measured by the positioning error and the RMS error.In the combined positioning part,double-frequency combined algorithms were introduced including smoothing pseudorange based on carrier phase.Then,three pseudorange combined algorithms were designed to operate combined positioning experiments.The efficiency of three algorithms was verified by contract experiment.The experimental analysis was focus on the effects of DBDS and combined positioning.Finally,a complete double-frequency combined DBDS based on single base station was established with 3D positioning accuracy raised up to decimeter-level from meter-level which proved the high-accuracy and high-stability of the DBDS based on double-frequency model.