Components 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 30 non-geostationary orbit satellites, providing two types of services, namely, open service and authorized service.

2. Ground control center system: it includes the main control, orbit measurement station, altimetry station, correction station and calculation center.

3、User equipment: According to the different user machines and application environments and functions of BeiDou, there are usually five types of BeiDou user machines: ordinary type. This type of user machine can only carry out positioning and point-to-point communication, which is suitable for general vehicles, ships and portable and other users' positioning and navigation applications, and can receive and send positioning and communication information, and communicate with the central station and other user terminals in both directions.

Communication type. Suitable for field operation, hydrological measurement, environmental testing and other types of data acquisition and data transmission users, can receive and send short messages, telegrams, and the central station and other user terminals for two-way or one-way communication.

Timing type. Suitable for users of timing, calibration, time synchronization, etc. It can provide tens of nanoseconds of time synchronization accuracy.

Command type. Command-type user machine is for a certain number of users of the higher group management department used, in addition to all the functions of the ordinary user machine, but also be able to broadcast broadcast information and receive the center of the control system sent to the user's location of the communication information. Command-type user machine can be divided into one, two, three. Among them, the first level of command-type user machine, the user under the jurisdiction of the ordinary user machine; the second level of command-type user machine, the user under the jurisdiction of the first level of command machine users; three levels of command-type user machine, the user under the jurisdiction of the second level of command machine users.

Multi-model user machine. This kind of user machine can not only receive Beidou satellite positioning and communication information, but also utilize GPS system or GPS augmentation system for navigation and positioning, which is suitable for users with high requirements for position information.