Key Technology Research Of GPS/BDS/GLONASS/Galileo Combined Pseudorange Point Positioning

With the development of the four global satellite navigation and positioning system,multi system data joint location becomes an inevitable trend.In this paper,the problems in the four system combined pseudo-range point positioning is studied and the positioning accuracy and stability are improved through the optimized design.It includes ionospheric delay correction,DCB correction,multipath error correction and the construction of stochastic model.Finally,the overall positioning performance of the whole system combined pseudo-range point positioning is analyzed.(1)The results show that the effect of the ionospheric delay correction by ionosphere-free is better than the model correction.The highest positioning accuracy of the ionosphere-free can be increased by 52% than model correction and the stability is enhanced.Therefore,the ionosphere-free is an ideal choice for dual frequency data.(2)The results of the satellite clock error correction by TGD parameters and DCB data are compared.The positioning results show that the DCB correction is better than TGD correction,and the positioning accuracy is increased by 10%.(3)The method that based on the satellite altitude angle is proposed for multipath effect.Through the experiment,it is proved that this method is feasible for the pseudo-range point positioning,and the highest positioning accuracy can be increased by 30%.Compared with the method of the double frequency pseudorange-carrier combined based on the cycle jump detection,the new method is more convenient in computation and higher positioning accuracy.(4)According to the characteristics of the different systems and the differences accuracy of the different satellites,a minimum of difference prior stochastic model is proposed.The results show that the model is better than the equal weight and the weight based on satellite elevation,and the highest positioning accuracy is increased by about 14% in this experiment.The estimation of Helmert variance component is used to calculate the weight ratio between the different systems.The results show that the robust solution estimation of Helmert variance component improve the positioning accuracy and weaken the influence of the gross error,the positioning accuracy is increased by about 10%.(5)Through the system optimization,the overall positioning accuracy of the four system combined pseudo-range point positioning is increased by 50% and the positioning accuracy is the highest than other combination methods.In complex environment,the positioning accuracy can reach 2m in horizontal and 5m in vertical.