Research On Ambiguity Fixing Algorithm Of Precise Point Positioning In Beidou Navigation System

Precision single point positioning is the technology of using a single GNSS dual frequency receiver to realize real-time or post-post-secondary high precision positioning by using the precise ephemeris and the precise clock difference,for short,PPP.The precise point positioning technology is mainly based on the GPS system.At present,there are relatively few researches on the combination of Beidou and Beidou and GPS PPP.In this paper,we use the existing PPP models and algorithms to design the solving strategy,carry out the Beidou precise point positioning research,analyze the positioning accuracy and convergence time.1.The basic theories and methods of precise point positioning are studied in depth.The linear combination of observation values and their respective characteristics are studied.2.The error sources and correction methods of precise point positioning observations are analyzed in detail.The parameter estimation method and mathematical model of precise point positioning are studied,mainly involving cycle slip detection and Calman filtering.3.We studied the fuzzy location algorithm for precise point positioning,including decimal fraction partial ambiguity degree algorithm and integer clock ambiguity algorithm.4.Based on the RTKLIB package,the precision single point positioning solution strategy is designed,using the traditional non ionosphere model,using the extended Calman filter(EKF)method to estimate the parameters,using the non ionospheric combined observation value,the satellite cut-off angle is 15 degrees,using the Saastamoinen model to correct the troposphere and the LLI cycle jump detection method,considering the model and the formula of the error correction and parameter estimation.Method.5.The precise point positioning of Beidou and Beidou combined with GPS is realized on RTKLIB.The experimental data of Beidou and GPS are tested and compared with two aspects of positioning accuracy and convergence time.The results show that the accuracy and convergence time of the combined observation value of the Beidou and GPS dual systems are better than that of the Beidou single system.Therefore,Beidou and GPS dual system combination observation is more conducive to improve precision and shorten the convergence time of precise point positioning.