Algorithm And Software Development Of GPS Virtual Reference Station

This dissertation made a specialized research on Algorithm of GPS virtual reference station, formed a system info from baseline solution of reference stations to generation and transmitting of virtual observations, and developed my software.The High precision differential positioning of GPS, goes through a phase of single based real time kinemtic differential system, runs to current phase of Network-RTK, VRS technology just is a research focus and development frontier in this field, it is one of the most latest promising concept,in a broad sense of using multiple reference stations. It calculates all kinds of errors through baselines among reference stations, and eliminates or lessens these errors by using some algorithm,which is applicable for centimeter-level accurate differential GPS positioning in real time environment.As opposed to the conventional single station applications,VRS technique lead to substantial improvements for positioning and navigation on the accuracy,service area coverage and system robustness.The realization of the VRS system also has to solve two basal questions, one is the generation of observed value (code pseudorange and carrier phase) of the virtual station, which depends on the accurate simulation of spatial correlative error; the other is the implement of data link, which guarantees the wireless communication between the control center and the user's receivers.This dissertation deeply analyzes algorithms on generation and broadcasting of VRS observations; in the field of ambiguity solution of baseline in network, firstly, analyzes influence of residual error of troposphere on baseline ambiguity solution, and uses least-square estimate and LAMBDA method, secondly, studies and achieved An Ambiguity Searching Method for Network RTK Baselines between Base Stations at Single Epoch, and compared the two methods; In the field of detection and reparation for cycle slips of carrier phase, improved a method which detects cycle-slip by L1 and L2 carrier phase, and achieves another method by selecting weighting matrix and fitting; compared two methods of generating virtual pseudorange and selected the better one; analyzes and calculates all kinds of spatial-correlation errors, and interpolates errors by using 1inear interpolation model; generated virtual observations of high precision; makes a research of data link of network RTK, RTCM SC-104 format is researched and a program of Coding/Decoding of RTCM data is developed. Developed an experimental software of VRS based on the algorithm to Verify the correctness and validity of the algorithm.