Research On BDS And GPS Positioning Algorithm

The joint positioning technology of Beirdou(BDS)and GPS is a hot topic of current research,which is beneficial to promote the BDS to the whole world and lay a foundation for the deep integration of BDS in China and other navigation systems.Since the positioning and solving module is a key part of receiver positioning,this thesis mainly studies and simulates the BDS/GPS positioning algorithm.The main work and innovations are as follows:Based on the BDS/GPS dual-mode receiver positioning research method and navigation teclhnology,the single point positioning technology,smoothing algorithm,system compatibility and error sources in positioning are analyzed in this thesis.The BDS/GPS dual-mode receiver positioning model is established.According to the user's motion state,the system state model of static users and low dynamic users is given.Aiming at a number of BDS/GPS dual-mode satellites and the increase of redundancy.Under the premise of analyzing existing star selection algorithms,an improved satellite selection algorithm based on satellite angle is proposed.The algorithm uses the maximum value of the cost function constructed by the inter-satellites line of sight vector to exclude satellites that play the same role in low elevation angles.The simulation comparison shows that under the condition that the precision of DOP value is excellent,the improved satellite selection algorithm has less amount of computation than other satellite selection algorithms.The result of positioning has low error and high precision.In the BDS/GPS dual-mode positioning solution,the single-frequency carrier phase smoothing pseudo-range method causes the filter divergence problem due to the initial value misalignment and the ionospheric error accumulation,and the carrier phase smoothing pseudorange method based on Kalman filter is introduced.The method can avoid the risk of filter divergence and improve the reliability of the positioning result.Secondly,on the basis of studying the least squares method and Kalman filter method,the least squares method and Kalman filter algorithm are combined.By initializing the Kalman filter and treating the positive definiteness and symmetry of the covariance matrix,the effectiveness of the joint solution algorithm is guaranteed.The simulation results show that the algorithm has low positioning error and high stability.In this thesis,the algorithms researched are verified by four aspects:satellite visibility,accuracy factor value,positioning accuracy and positioning speed.The simulation results show that the BDS/GPS dual-mode positioning results have small error,real-time performance good and high stability.The DOP value is at most 2.6135 and the average error on all three axes are less than 2.2 meters.