| The location service based on satellite navigation system can be applied to all aspects of transportation,and the demand for high-precision navigation and positioning services is increasing gradually.The traditional differential positioning technology can meet the positioning requirements,but it needs to deploy a certain density of differential base stations,which is not conducive to reducing the construction cost.Precise Point Positioning(PPP)uses a single satellite receiver to achieve high-precision measurement results,which can not only ensure positioning accuracy,but also reduce the use of differential base stations and reduce construction and maintenance costs.The traffic environment is complex and changeable,and the satellite positioning system is easily affected by tunnels and urban buildings,leading to the decrease of visible satellites,and the satellite positioning cannot meet the requirements of availability and continuity.The regional navigation system is a ground-based auxiliary positioning system similar to the satellite positioning system,which can assist the satellite positioning system to improve the positioning accuracy and continuity when the satellite signal is blocked.Therefore,in order to further improve the positioning accuracy and convergence speed of PPP,the ambiguity fixing method of precision point positioning is studied.A method of regional navigation system assisting precise point positioning has been studied to effectively solve the problem of positioning availability and continuity in the environment where the satellite signal is blocked.The main work includes:(1)The basic process of PPP and analyzes the main error sources and correction models of PPP are summarized in this thesis.On the basis of the single-differenced ionosphere-free PPP model,an extended Kalman filter algorithm based on ambiguity floating point solution is constructed to realize online estimation of motion state.(2)The reasons for the non-integer characteristic of PPP ambiguity is analyzed,also cascaded ambiguity fixing method is studied in this thesis.Firstly fixing the ambiguity of wide lane,then fixing the ambiguity of narrow lane,and finally fixing the single-differenced ionosphere-free ambiguity.The positioning performance of PPP with fixed ambiguity is verified and analyzed.(3)The carrier phase positioning method of the regional navigation system is studied in this thesis.Based on the single-differenced carrier phase observation,a combined positioning method of the regional navigation system/PPP is designed,and the positioning performance of the tight combination system under different number of available satellites is verified and analyzed.(4)The integrated positioning software of satellite/regional navigation system based on C# language is designed and developed,and its functional requirements and interface requirements are analyzed in this thesis.Then verifies three positioning algorithms: PPP,ambiguity fixing of PPP and tight integrated positioning of regional navigation system/PPP by using experimental data.The experimental results show that comparing with the floating solution,the convergence time of PPP fixed solution with cascaded ambiguity fixing method is reduced from 800 s to 750 s,the north error RMS is reduced from 0.053 m to 0.019 m,and the east error RMS is reduced from 0.09 m to 0.063 m.In the case that the number of available satellites does not meet the positioning conditions,the horizontal error of the regional navigation system/PPP tight combination positioning method is within 30 cm,which can ensure the availability of positioning in the signal blocking environment.This thesis contains 51 figures,9 tables,and 63 references. |
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