Precise Point Positioning Related Technical Problem Research

GPS Precise Point Positioning(PPP) is a hot research, PPP is easy to operate, and does not depend on the other reference stations, it plays an important part in the near-earth satellite orbit determination and investigation. therefore,PPP is good in theoretical significance and practical value. PPP requires precise satellite orbit and satellite clock error, and it needs to download precise ephemeris and precise clock provided from IGS. In addition,we need to interpolate ephemeris and clock error to get the data information. There have been a variety of methods for interpolation which can be achieved with a relatively high accuracy. It also need to get the precise distance of the satellite which is related to the station errors, satellite related errors and propagation path related errors.So we must make the corrections such as the earth’s rotation correction, satellite antenna phase deviation, Ionospheric delay and tropospheric delay. Moreover,week jump and large gross error signal may occur in the dissemination process,so data must be preprocessed. Parameter estimation is also important in PPP,which purpose is to calculate the unknown parameters. There are many methods such as Kalman filtering, least squares and sequential adjustment right now. Based on the above knowledge,I carried out the study. The main research of this thesis are as follows:First:To investigate three position models for PPP:the traditional model, UofC model and no ambiguity model. It analyzes error correction model and data preprocessing methods which are required in PPP.It also introduces and compares the data preprocessing methods and parameter estimation methods.Second:In this thesis, high order difference method, phase minus code pseudo-range, Ionosphere residual error method and the M-W have been applied in cycle slip detection.And analysis of these four methods are compared. The M-W and Ionospheric residuals are composed in this thesis so that it better to detect cycle slip.Third:The size of the rotation of the earth model corrections, the effect of the relativity theory and the tropospheric delay correction are analyzed.Meanwhile, it studies the main factors that affect the size of the error.Fourth:Comparing the impact of the different initial values of the Kalman filtering, according to the experimental data, the relationships of noise array, matrix of the process noise, gain matrix and prediction covariance matrix are studied.Fifth:This thesis based on matlab7.0as a programming tool to uses the least squares estimation and Kalman filter algorithm for data processing. Kalman filtering has high solution precision, and after convergence the single epoch is also high precision.So kalman filtering is not only suitable for static single-point positioning but also suitable for the kinematic single point positioning. Using rapid ephemeris and final ephemeris for Kalman filter calculation, we find that using the final ephemeris is better than rapid ephemeris, but the rapid ephemeris and the final ephemeris solver are basically the same. So in the case of a less demanding and time emergency,we can directly use the rapid ephemeris.