Research On Theory And Realization Of Gnss Precise Point Positioning

The research of high-accuracy GNSS single point positioning is one of theGNSS advanced topics. Continuous improvement of the models of GNSS PrecisePoint Positioning (PPP) data processing makes PPP have been widely used invarious fields. However, the cycle slip detection and repair and ambiguity resolutionare still insufficient. GNSS PPP cycle slip detection and repair and a new ambiguityresolution method are proposed in this paper. A GNSS PPP software was developedto verify the reliability and validity of the proposed new methods. The main contentsand conclusions are as follows:1) The main difference between Precise Point Positioning and differentialpositioning is more error sources need to be corrected in the GNSS PPP solution. Weanalyzes the error characteristics and mechanism of GNSS PPP and the affections onthe solution. The optimal correction model of improve the accuracy of GNSS PPPwas determined by comparing the results of different experiments in differentmodels.2) Data preprocessing methods directly affect the convergence speed of Kalmanfilter and positioning accuracy and reliability of GNSS PPP, cycle slip detection andrepair is an essential issue. GNSS PPP Non-difference observation cycle slipdetection and repair were researched. A new method based on empirical modedecomposition (EMD) outlier detection cycle slip detection was proposed. In thismethod, the information of observation signal characteristic and its abnormality wasanalyzed. By detecting the signal abnormality to determine the values and locationsof the cycle slips. The applicability of the method was discussed by some examples;3) The TECR/MW combined cycle slip detection and repair algorithms werestudied in this paper. Generally speaking, the total electron contents rate (TECR)cannot accurately detect a larger sampling interval (eg.30s) cycle slips. An improvedmethod was proposed by using TECR predicted and measured values of the residualto eliminate TECR time items. Experimental results shows that: the improvedTECR/MW combined cycle slip detection and repair algorithm make full use of theadvantages of two algorithms and improve the efficiency of cycle slip detection andrepair. For any sampling interval, any size, and different combinations of cycle slipscan be detected and repaired effectively;4) The up-to-date methods for ambiguity resolution at a single receiver werereviewed. Then the relationship between float ionosphere free ambiguity, wide lane ambiguity and narrow lane ambiguity was analyzed and a new PPP ambiguityresolution without reference stations was proposed. The global IGS stations and astation in CUMT were selected to verify the new method. ITRF coordinates providedSOPAC and GAMIT solver results were used as the reference values of selected sites.Experimental results shows that: the proposed PPP ambiguity resolution algorithmnot only improves the positioning accuracy but also decreases the absolute residualsaccording to the reference coordinates.5) The differences between GLONASS and GPS data processing were alsoresearched. By analyzing the different of the GPS/GLONASS PPP and GPS PPP, theGPS/GLONASS PPP calculation was established. The results shows that theGPS/GLONASS satellite distribution can be optimized when GLONASS satellitesadded, when there are fewer GPS satellites the applicability of PPP can be improved.Due to the accuracy of GLONASS ephemeris and clock errors, accuracy ofGPS/GLONASS PPP positioning has not been significantly improved comparedwith GPS PPP.6) A GNSS PPP software with a welcome UI was developed with Matlab tools.The software can conduct GPS PPP, GNSS PPP float and fixed solution with twokinds of solution with solver mode. The proposed cycle slip detection and repair andambiguity resolution method were also validated by the software.