Research And Implementation Of Combined BDS/GPS Precise Point Positioning

Precise point positioning(PPP) is a position technology to obtain the high precision positioning coordinate of fixed point by calculating the observation data including the precise satellite ephemeris and satellite clock error that collected by single GNSS receiver.With its single operation,the PPP technology can operate without distance limitations and also can obtain many advantages station products such as fixed point coordinate, troposphere delay, ionosphere and others that has broad prospects for development.PPP play an important role in many fields such as surveying and mapping.Though it has many advantages,there exists many problems such as too many parameters in the solution model, long time to convergence and having lower positioning accuracy than the difference differential positioning.Today is an age that coexists multiple satellite navigation and positioning systems.The vigorous development of satellite navigation and positioning system brings both opportunities and challenges. Given the PPP problem, the research of the multiple satellite navigation systems combination to solve PPP question for improving the positioning accuracy and reducing the convergence time is one urgent question to solve.Basedon the study of the basic theory of GPS and BDS, this paper firstly describes the basic principle of BDS/GPS combination of PPP and gives the observation equation of BDS/GPS combination of PPP, and then deduces the BDS/GPS combination of standard single point positioning model and its solution process;according to the difference in the solution of dual frequency PPP and single frequency PPP, this paper deduces two case of BDS/GPS combination of PPP model respectively and summarizesthe parameter estimation methods.The error source of the PPP and its solving methods are described systematically in this paper.Based on the BDS/GPS combinationof PPP theory, this paper analyzes the performance of BDS/GPS combinationdual frequency PPP and the single frequency PPPby processing experimental data.In BDS/GPS combination of dual frequency PPP,when we have favorable conditions of satellites, the addition of BDS cannot help GPS to get better solution results in convergence time and accuracy, but when the GPS satellite number is less, the addition of BDS to the GPS have improvement in the convergence process;in the BDS/GPS combination of single frequency PPP, when we have favorable conditions of satellites, adding BDS to GPS has little effect to the convergence time in the solution but significantly improves the positioning accuracy. Under the condition of less number of GPS satellites, BDS data, whether in the position of convergence time, or in the positioning accuracy, can play a significant role and get a good result.