The Research On Precise Point Positioning Of Beidou Navigation Satellite System

The technology of PPP(Precise Point Positioning) possesses the characteristic of high accuracy. With the precise satellite orbit and satellite clock offset products of global several observation stations, PPP can achieve the positioning accuracy of centimeter in static mode, accuracy of decimeter in dynamic mode. The majority of the research on PPP at the present is based on GPS or GLONASS. BDS(Beidou Navigation Satellite System) is developed by the government of China, beginning to offer the positioning and timing service for Asia-Pacific region. As the strategic industry, BDS plays a vital role in the protecting the social security and economic construction and promoting the informatization development. The main application of BDS is the high-precision positioning based on carrier phase observation in the future. In this paper, the key technology of PPP is researched, feasible project is proposed and the feasibility and accuracy of PPP based on BDS are discussed.The main work in this paper is summarized follows:The fundamental theory of PPP is expounded firstly, the principles, characteristics and implementation of the key technology such as the establishment of mathematical model, the error correction, cycle-slip detecting, Extended Kalman Filter(EKF) estimation and the fixing of ambiguity are researched.The combination of forward and backward filter is used to improve the accuracy of the EKF. The simulation and analysis are implemented in the paper. The combination method is successfully applied in the PPP application of BDS.The ambiguity is always not an integer of the ionosphere free model. In this paper, the method based on integer clock separates the FCBs from the ambiguity parameter, the wide lane ambiguity is fixed to integer, and thus the ambiguity of ionosphere free model is fixed. This method improves the accuracy of estimation and convergence time.The PPP software is developed in the paper, including the module of reading file, data pre-processing, error correction, EKF estimation, ambiguity resolution and results exporting. With the original data of BDS observation stations, the performance of the algorithms and the function of the software are verified and analysed.