Research On GNSS Multi-system High Precision Pseudo-range Single Point Positioning

In the modern applications of global navigation satellite system(GNSS),the accuracy and robustness of positioning technology are the key factors of the positioning system.Pseudorange single-point positioning(SPP)utilizes the pseudo-range observation of the satellite can easily achieve high robust meter-level positioning accuracy with a single receiver.Therefore,pseudo-range single-point positioning still plays a vital role.However,the traditional SPP algorithm can only achieve meter-level positioning accuracy,which is not enough to satisfy the demands of some modern applications.With the rapid growth of GNSS,the user receiver can obtain some error correction files related to the satellite through the Internet,such as precise orbit and precise clock error files,to improve SPP’s positioning accuracy.In recent years,SPP positioning algorithm has been studied in an endless stream,including adding new observations,changing parameter estimation methods,and introducing additional constraints.Aiming at the application scenarios where the receiver altitude can be obtained in advance as a priori value,such as hydrology and vehicle surface activities in the airport,etc.,this paper proposes a pseudo-range single-point positioning algorithm based on altitude constraints,which has high accuracy and high robustness.This algorithm can further improve the performance of SPP positioning and enhance the robustness of SPP positioning technology.The thesis focuses on the non-linear altitude-constrained pseudo-range single point positioning algorithm.The main contents are as follows:Firstly,based on the basic GNSS positioning principle and error correction methods,the SPP’s basic theories are systematically summarized,including the common pseudo-range observation model and linearization methods,error correction,and parameter estimation methods for navigation.Secondly,a quadratic equality constraint is introduced,and the prior altitude constraint is incorporated into the SPP algorithm.Therefore,a new SPP positioning method based on the least squares with a quadratic equality constraint is proposed.SPP experiments are carried out using the actual GNSS satellite observation data.The results show that compared with the unconstrained SPP,this method can greatly improve the positioning accuracy and has higher robustness,which is independent of carrier phase measurement.Thirdly,considering that a prior altitude value usually contains a certain error in the actual measurement process,thus an SPP algorithm with weighted altitude constraint evolved from the SPP algorithm with quadratic equality constraint is proposed.Furthermore,the way of solving the nonlinear constrained LS estimation is introduced.The SPP’s positioning performance is verified by experiments.Fourthly,introducing a method of SPP positioning solution based on the moving horizon estimation(MHE).Combined with the nonlinear altitude constraint equation,the constrained MHE algorithm is used to solve the unknown parameters in SPP positioning,so as to further improve the performance of SPP positioning.The results show that the MHE filter estimation algorithm can greatly improve SPP’s positioning accuracy.