Main components of GPS satellite positioning

GPS is mainly composed of three parts: space satellite constellation, ground monitoring station and user equipment.

The 1.GPS space satellite constellation consists of 2/kloc-0 working satellites and 3 in-orbit standby satellites. The 24 satellites are evenly distributed on six orbital planes, with an inclination of 55, an average altitude of 20200km and an operating period of 1 1 h58min. The satellite uses two L-band radio carriers to continuously send navigation and positioning signals to users. Navigation and positioning signals contain the position information of satellites, making them dynamic known points. In any place on the earth, at any time, above the altitude angle of15, an average of 6 satellites can be observed at the same time, up to 9 at most. GPS satellites generate two sets of codes, one is called C/A code (Coase/Acquisition Code11023 MHz) and the other is called P code (Procesecode10123 MHz).

2. The ground control part consists of a main control station, five global monitoring stations and three ground control stations. The monitoring station is equipped with an accurate cesium atomic clock and receiver, which can continuously measure all visible satellites. Satellite observation data obtained by the monitoring station, including ionospheric and meteorological data, are transmitted to the main control station after preliminary processing. The main control station collects the tracking data of each monitoring station, calculates the orbit and clock parameters of the satellite, and then sends the results to three ground control stations. The ground control station injects these navigation data and the commands of the main control station into each satellite running overhead. This injection is once a day for each GPS satellite, and the last injection is made before the satellite leaves the injection station. If a ground station fails, the navigation information pre-stored by the satellite can still be used for a period of time, but the navigation accuracy will gradually decline.

3.GPS user equipment consists of GPS receiver, data processing software and its terminal equipment (such as computer). According to a certain cut-off angle of the satellite height, the GPS receiver can capture the signal of the selected satellite to be measured, track the operation of the satellite, exchange, amplify and process the signal, and then calculate the three-dimensional coordinates of the GPS receiver center (station) through baseline calculation and network adjustment by computer and corresponding software. The structure of GPS receiver is divided into two parts: antenna unit and receiving unit. At present, various types of receivers are getting smaller and lighter, which is convenient for field observation.