Theoretical Basis of GPS Vehicle Satellite Positioning

　　1. Overview of System Implementation Theory

　　GPS currently has 24 satellites in the space satellite constellation, including 21 working satellites and three spare satellites in orbit. Each satellite is equipped with 4 high-precision electronic clocks, which provide high-precision time standards for GPS positioning. User equipment is mainly composed of GPS receiving hardware and data processing software, as well as microprocessor and its terminal equipment.

　　The GSM network is the most widely used wireless communication network in China. It has fast transmission speed, low price for single data transmission, does not occupy voice, and its two-way transmission performance can easily realize information collection and remote control of the collection station equipment, and realize remote control and telemetry. Therefore, it is very reasonable to use GSM for wireless communication.

　　2. System implementation scheme design

　　In the design, Trimble's GPS module is used for car positioning, and two Siemens GSM modules are used for wireless data transmission between the car and the PC. The setting of the car part is completed through key input, and the current information is displayed by liquid crystal. , and use the serial port to communicate with the GSM module on the PC, and then display it on the electronic map based on the VB platform.

　　This system realizes the simulation operation of GPS vehicle positioning system. Using GSM as the data transmission medium, the experimental car replaces the actual vehicle, and the PC is used as the vehicle control center to process the position information of the car and instruct the movement of the car. After the software test system, the collection of the position of the car is realized, and the command can also be received and executed by the car.

　　The author's innovation point: integrate the three technologies of single-chip microcomputer, GPS and GPRS, and apply it to the vehicle monitoring system reasonably and effectively, realize the real-time monitoring and dispatching of the vehicle, and improve the safety and operation efficiency of the vehicle. The system has been running on our school's campus patrol car system, saving nearly 10,000 yuan for the school. Practice has proved that the communication function of the system is reliable and reasonable in design.

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GPS navigation satellite has a high-precision atomic clock for time service