The operation of the car navigation system mainly relies on the global positioning system (GLOBAL POSITIONING SYSTEM, GPS for short).
GPS is composed of three parts: space satellites, ground monitoring and user reception. There are 24 satellites in space forming a distribution network, which are distributed on 6 quasi-synchronous orbits with a tilt angle of 55° and 20,000 kilometers above the ground. Each orbit has 4 satellites. GPS satellites orbit the earth every 12 hours, enabling any place on the earth to receive signals from 7-9 satellites at the same time. There are 1 main control station and 5 monitoring stations on the ground responsible for the monitoring, telemetry, tracking and control of satellites. They are responsible for observing each satellite and providing observation data to the main control station. After receiving the data, the master control station calculates the precise position of each satellite at each moment, and transmits it to the satellite through 3 injection stations, and the satellite transmits the data to the ground through radio waves to the user receiving end equipment .