Research On BDS/GPS Dual-mode Positioning Algorithms

With the continuous development of navigation technology,many navigation systems coexist today.At home and abroad,the multi-mode localization algorithm has been studied,and some research results have been achieved.However,in multi-mode positioning,there are differences among multiple navigation systems.At the same time,with the increase of the number of observable satellites,the probability of outliers and the amount of computation in the process of PVT calculation by the receiver will also increase,which will affect the positioning accuracy and real-time performance of the receiver.Therefore,this paper studies BDS/GPS dual-mode positioning algorithm to reduce the impact of system differences between BDS/GPS on PVT solution,remove the observation of outliers and select appropriate satellites to participate in PVT soluti on,so as to ensure the positioning accuracy and real-time performance of the receiver.In this paper,the theory of BDS/GPS dual-mode localization algorithm is studied.Firstly,data fusion is the first step to realize multi-mode positioning.This paper analyses the data fusion method of BDS/GPS dual-mode positioning,focusing on the influence of data fusion method on TTFF.Secondly,the least square method is a commonly used PVT method for navigation and positioning,but it also has the disadvantage of no t linking the two time positioning together,which leads to the disorder of positioning results.Aiming at this problem,this paper studies the implementation of Kalman filter in BDS/GPS dual-mode positioning in detail,describes the specific modeling process and implementation steps,and analyzes the advantages of Kalman filter in the PVT solution of BDS/GPS dual-mode positioning through simulation experiments.Thirdly,this paper analyses the influence of outliers on PVT solution when pseudo-range and Doppler observations occur,and studies the outlier detection algorithm,uses the relationship between information variance matrix and observations in Kalman filter to judge outliers,and verifies the validity of the detection algorithm through simulation exp eriments.Fourthly,the computational pressure of dual-mode receivers will be increased and the real-time performance will be affected by the simultaneous observation of multi-mode receivers.In this paper,a star-picking algorithm based on pseudo-gravity center is studied.The simulation results show that the star-picking algorithm in this paper is more sensitive to the spatial distribution of satellites than the star-picking algorithm based on azimuth and elevation angle.Satellite observations participating in the PVT solution can ensure the positioning accuracy and meet the real-time requirements.In order to verify the feasibility and validity of the above research in the actual receiver,all the above simulation algorithms in MATLAB are implemented on the BDS/GPS dual-mode receiver based on SoCFPGA,and the experimental results show that the algorithm can achieve better positioning accuracy and real-time performance in practical application.