The Research Of GPS Real-time PPP Technology

This paper has researched on related technologys of GPS real-time precise pointpositioning(real-time PPP). it includes the method of ultra-rapid precise ephemeris’s receiving intime which issued by IGS, and utral-rapid precise ephemeris interpolation,and the mathematicmodal and its error’s correction,and data pretreatment and parameter estimation,etc. Inaddition,the paper has reaserched data acquiring and analysis base on OEM card,and used it inprocedure of real-time precise point positioning.Real-time precise point positioning with precise point positioning of the greatest differenceis that the former acquiring the current epoch result in real-time processing,and the latter is to getthe result after the whole observation finished and processing.The main content and conclusions in this paper is Showing as follows:(1) Real-time Precise Point Positioning Model and Error Correction.This paper introduced two observation model of the real-time precise point positioning, theone was the model modal of ionosphere free and another was the UofC model. It was to use halfsum of phase and pesudorang model as the observation model to process in paper. The model ofhalf sum of phase and pesudorang can effectively to reduse the ionosphere delay and observationnoise in observation data.(2) Utral-rapid Ephemeris Acquring in Real-time.Because precise ephemeris has been stored in FTP of IGS on internet,and its name andstorage path has a certain rules.So the paper include the technology of how to get the ultra-rapidephemeris from IGS in real-time.(3) The Selection and Comparison of Ultra-rapid Ephemeris Interpolation.This paper has reaserched that interpolation‘s minimum fit order of the result come up tosufficient accuracy which has get from processing used Lagrange interpolation,continuedfraction interpolation,Aitken interpolation and least square fitting function respectively.And tohave a comparision and analysis from the execution time and location effect of all interpolationalgorithm,the conclution shows that the result which has gotten from processing used continuedfraction interpolation is poor and it can not be used in real-time precise point positioning.(4) Rectangular Areas of Least Squares Surface Fitting Extrapolating Ionospheric Grid Value.This paper introduced steps how to extrapolate ionospheric gird value used rectangularareas of least squares surface fitting. From the computational example,it can be used toextrapolating ionospheric grid value and it would Provides an effective route for ionosphericdelay correction of single-frequency real-time precise point positioning. (5) Cycle Slip Detection and Restoration.This paper mainly reaserchs include the multi-frequency carrier-phase/pseudorangecombination to detect the cycle slip and gross error.Through the computational example,theresult shows it is not only to a series of large cycle slip but also to a series of small cycle slip canbe precisely detected and repaired by this method.(6) Parameter Estimation and Integer Ambiguity ResolutionThis paper mainly reaserchs include introducing Kalman Filter and integer ambiguityresolution used kalman filter.According to the deficiency of the traditional kalman filter,thepaper finaly choose Forward and Reverse Kalman Filter as the parameter Estimation method.(7) Application of GPS Real-time PPP Base on OEM Board Card.This paper has reaserched on data extraction and analysis base on NovAtel OEMV-2boardcard,and add a real-time precise point positioning module in software RTPPP. The procedure ofthe module decoding the current positon of the receiver’s antenna through acquisition andanalysis original observation from OEM board card is the final form of the real-time PPP.(8) Software Design and Compiling of Real-time PPP.Base on technology of real-time precise point positioning, this paper has designed andcompiled the software of GPS real-time precise point positioning. The software is in addition toreal-time precise point positioning function outside,it still has the function of TimeConversion,Coordinate Transformation,Serial Ports Debugging,Ephemeris Extracting,Ionospheric Grid Extracting and IGS Data File Downloading and so on.(9) Software Accuracy Evaluation.To identify the positioning accuracy of GPS real-time precsize point positioningsoftware,this paper has done a series of experiments,it contains static positioning experiment anddynamic positioning experiment. In dynamic positioning experiment,it contains static copydynamic positioning experiment,airborne experiment,Ship experiment and Rigid body rotationexperiment. From these experiments,the result show the accuracy of static and dynamicpoisoning were0.02~0.09m and0.5~2.0m respectively.So,it was in precision of sub-secimeterfor static positioning and in precision of sub-meter to meters for dynamic positioning.