Design And Implement Of Simulation System For GPS Observed Data

GPS is an all-weather and high-precision global positioning system, with a widerange of application markets and development prospects. Satellite navigation signalsimulator is used to simulate the various scenes of GPS satellite signals, plays animportant role in the development and testing of GPS receivers. Because of some keytechnology is sensitive to this subject, the domestic research institutions is stillness. Thispaper is researched on the satellite navigation signal simulator of GPS.The task of this subject is research and simulation of the key technology for theGPS signal simulator, including complete the conversion of time system and coordinatesystem, deal with the broadcast ephemeris, extrapolate the satellite orbit, transmissionerror and the observation value. Combined with the software interface, it could acquirethe observation data with any modification of observation time, location, environmentand other parameters.Firstly, this paper researched the mathematical model of GPS observation data.Time systems, coordinate systems and the conversion formulas between them have beengiven. After that is about the satellite orbit, it analyzed the principle and orbitalparameters of satellite operation, the structure, content and the ephemeris of GPS.According to the error correction of receivers, the various sources of error in thesimulation system is analyzed, such as GPS satellite clock error, ephemeris error,ionosphere delay error and tropospheric delay error, to make the simulation morerealistic.Then, based on the structure and function of the satellite navigation signalsimulators, it put forward the requirements and basic framework of the simulationsystem for GPS observation data. According to the algorithm, the implementation ofeach module in detail is discussed, included the processes: using the acquired ephemeristo extrapolate satellite position, determination of satellite visibility, iterative calculationfor pseudo-range observations and orbit fitting. The hybrid programming of the Matlaband VC++6.0software is developed, to realize visualization operations of this GPS navigation signal simulation system. The observation point have been set, the systemcould carry out the simulation result.At last, the simulation software needs to be tested. With the observation data isobtained, unit level validations of satellite orbit, atmosphere propagation delay andpseudo-range that generated by simulation system were carried out, to verify therationality of the design and validity of the key algorithm.The main result of this research is using software programming to achieve a morecomplete, feasible navigation signal simulation system for GPS. This simulation systemis used for generic type receiver test, and it could continue to expand and research, evendesign and development for other global positioning system with the similar principles.