Overview of China's Beidou Navigation and Positioning System

The BeiDou navigation and positioning system (referred to as the BeiDou system) consists of three parts: the space constellation, the ground control center system and the user terminals.

1. Space constellation

The space segment of China's Compass/BeiDou navigation system (COMPASS) under construction is planned to consist of five geostationary orbit satellites and thirty non-geostationary orbit satellites, providing two types of services, namely, open service and authorized service. The satellites are 36,000km away from the ground and are located over the equator at 80 and 140 East longitude, respectively, to carry out the task of relaying two-way radio signals between the ground control center and the user terminals. There is also a backup satellite positioned over the equator at 115.5 East. The satellite weighs 980kg and has a lifetime of not less than 8 years.

2、Ground Control Center System

The ground control center of BeiDou system includes the main control, orbit measurement station, altimetry station, correction station and calculation center, which is mainly used to measure and collect correction navigation and positioning parameters, complete orbit measurement and adjust the satellite's operation orbit, attitude, prepare ephemeris, form user positioning correction data and position the user, i.e., it is responsible for the transmission and reception of the radio signals as well as monitoring and managing the whole working system.

3、User equipment

According to the BeiDou user machine and the application of different environments and functions, usually there are five types of BeiDou user machine:

Ordinary type, communication type, timing type, command type and multi-model user machine.