Gps Precise Point Positioning

Precise Point Positioning (PPP) is a new GPS technique developed in the last few years, which use precise ephemeris and precise saellite clock information .This methods uses undifferenced dual-frequency pseudorange and carrier phase observations, for stand-alone precise geodetic point positioning(static or kinematic) with centimeter precision in the Internatonal Terrestrial Reference Frame(ITRF). PPP is very useful for the orbit determination of LEO satellite, wide area geoscience rearch and national land resource investigation, which is the hot topic of GPS presenctely. This thesis focuses on the theory and algorithm of PPP.At the same time, it discusses the key technique in many ways ,including unknow parameter estimation, the defintion of random error model, and undifferenced data processing, etc. Finally a function made by MATLAB is used for verification and analysis for PPP related problems from a huge observation data.In the PPP methods, it use observations from IGS tracking station to calculate satellite orbit and satellite clock error firstly, then using satellite orbit and stallite clock error process stand-alone receiver station data. A final static positoning has an accuracy of centimeter and kinematic positioning with d-meter precision.Since PPP use undifferenced data, so the error cannot be estimated by differenced, only by model or estimation with position parameter. So, the problem of cycle slip detection and removal is more difficult than differenced model. This paper use of the M-W combination to probe and fix the widelane cycle slip effectively.The function directly utilizes 15 minutes interval precise satellite ephemeris and clock products provided by International GNSS Service(IGS) .Using Lagrange polynomial interpolation ,it can compute 3 dimension satellite coordiantes and precise satellite clock for the epoch when GPS signal is transmited . It is easier for realization compared with the method by mechanial orbit model and the performances are similar. By adopting the more accurate Niell model to correct the tropophere delay , it further increases positioning precision.Finally, by analyzing the computed result from data sets of IGS tracking stations ,the conclusion is summarized.