Research On GPS/BDS Combined Dynamic Precise Point Positioning

Precise point positioning does not need a reference station,but only needs a receiver to obtain high positioning accuracy.Because precise point positioning has the advantages of high accuracy,not affected by baseline length and low operation cost,it is widely used in navigation,positioning,engineering measurement and other fields.At present,the research of static precise point positioning has become mature,while the research of dynamic precise point positioning is still insufficient due to the complex motion process.The traditional single satellite positioning system can not cope with some complex environment(urban canyon,etc.).In some complex environment,the satellite structure distribution is poor and the number of available satellites is relatively small,and the accuracy and reliability of satellite navigation and positioning has a direct relationship with the number of satellites tracked,so the multi satellite system combined positioning can solve this problem well.Based on this,this paper makes a deep research on GPS/BDS combined dynamic precise point positioning.The main research contents and results are as follows:(1)This paper systematically summarizes the basic principle of precise point positioning,including basic observation,time and space system,common PPP model,cycle slip detection.This paper introduces the common error sources and correction methods of satellite,receiver and propagation path in precise point positioning.(2)Two kinds of GPS/BDS dynamic precise point positioning models,uncombined and ionosphere free,are derived,and the positioning performance of the two PPP models in dynamic positioning is compared.The result shows that in dynamic precise point positioning,the convergence and positioning accuracy of the ionosphere free model is slightly higher than that of the uncombined model,but both models can achieve the positioning accuracy of horizontal better than 0.05 m and vertical better than 0.1m,and both models can guarantee the accuracy requirements of dynamic positioning.At the same time,the convergence and positioning accuracy of GPS/BDS combined dynamic precise point positioning are improved compared to GPS and BDS single systems.(3)In this paper,the square root information filter is used as a parameter estimation method in GPS/BDS dynamic precise point positioning,and compared with the common extended kalman filter.The result shows that the square root information filter is superior to the extended kalman filter in positioning accuracy,convergence and computational efficiency.(4)Through three experiments of static simulation dynamic(different satellite cut-off angles),short-distance walking,and vehicle urban environment,the positioning performance of GPS/BDS dynamic precise point positioning in a complex environment is evaluated.The result shows that GPS/BDS combined dynamic precise point positioning has more visible satellites and better satellite spatial structure than GPS and BDS single system.At the same time,compared with GPS and BDS single system,the improvement of positioning accuracy and convergence of GPS/BDS combined system is more obvious in the case of signal occlusion than in the case of no occlusion,which indicates that the combined system PPP is very suitable for solving the problem of poor positioning accuracy of single system in complex environment.