Study On Single-frequency GPS Precise Point Positioning

Precise Point Positioning is a high-precision GPS single point positioning technology, it only uses a GPS receiver's observations, combined downloaded from the IGS stations precise satellite ephemeris and precise satellite clock error file, using the observed received pseudorange and carrier phase observations to calculate to get the receiver's exact coordinates in the earth coordinate system, the positioning accuracy can be achieved even centimeters. According to the observing of receiver, the method has a difference of dual-frequency precise point positioning and single-frequency precise point positioning. In the single-frequency precise point positioning, you need to get to the precise satellite orbit and satellite clock error value, then consider the the various sources of error impacting on positioning results and the corresponding correction modeling. In the post-processing it can also be combined with IGS stations's precise ephemeris to obtain high-precision satellite orbit, combined with IGS stations's satellite clock errors file to get effectively clock error correction. Other error sources have the corresponding correction models, in which the ionosphere delay error on the single-frequency single point positioning accuracy is the maximum, it should be carried out in-depth study. In calculating process, preprocessing work is gross errors detection, cycle slip detection and repair, phase-smoothed pseudorange data, and then the next work is estimating the unknown parameters using the Kalman filter. The single-frequency precise point positioning research work of this paper are:(1) introduced the single-frequency precise point positioning of the basic content, including the establishment of observation equations, observations'combined method, error sources and correction of model.(2) The impact of ionospheric delay has the greatest impact on the single frequency PPP, this article focuses on introducing a variety of ionospheric correction models, the ionospheric grid model interpolation methods and the establishment of a small region of the ionosphere model fitting methods introduction. Using case analysis, getting that by adding the unknown parameters of ionospheric parameters can achieve good results.(3)discussed the single-frequency precise point positioning's three methods of detecting the cycle jump:pseudorange/carrier combination method, the carrier rate of change and the stars intercropping difference Polynomial. Calculated with examples show s that the satellite intercropping difference polynomial method is better than the other two methods results, recommended when making cycle slip detection with a variety of methods to combine. (4) introduced the single-frequency precise point positioning's mathematical model and parameter estimation methods, focusing on the standard Kalman filter to estimate the unknown parameters. Introduced the robust Kalman filter for the case that the observed data may has gross error in the process of calculating parameters. Program with matlab throughout the single frequency PPP process.