What are the four major satellite navigation systems in the world?

1. American Global Positioning System (GPS). It consists of 24 satellites, which are distributed on six orbital planes, and the intersection points are 60 degrees apart, and the accuracy is about 10 meter. It is used for military and civilian purposes, and the second generation satellite system is currently being tested. American Global Positioning System (GPS) is the most widely used and mature navigation and positioning system in the world. At present, there are 30 and 4 kinds of navigation satellites in the GPS space segment. 1in March, 1994, a navigation constellation consisting of 24 satellites was launched, marking the official completion of GPS.

2. Russian GLONASS: Strong anti-interference ability. It consists of 24 satellites with an accuracy of about 10 meter. Dual-use, the service scope is designed to expand to the whole world by the end of 2009. It is also a dual-purpose navigation and positioning satellite system developed and controlled by the military. Although its positioning accuracy is slightly lower than that of GPS and Galileo, it has the strongest anti-interference ability. GLONASS was initiated by the Soviet Union in 1976.

3. Galileo system in Europe. It consists of 30 satellites, and its positioning error is less than 1 m, which is mainly used for civil use. The first experimental satellite was successfully launched in 2005. It is expected that location service will be opened before 2008; Galileo positioning system is a satellite positioning system under construction in the European Union, which is called "European version of GPS". Galileo launched a total of 30 satellites, of which 27 were working satellites and 3 were backup satellites. In addition to 30 medium-altitude circular orbit satellites, the system also has two ground control centers.

4. China Beidou system. It consists of 5 geostationary orbit satellites and 30 non-geostationary orbit satellites. The positioning accuracy is 10 meter. It is planned to cover China and its surrounding areas around 2008, and then gradually expand into a global satellite navigation system.

Beidou satellite navigation system is a global satellite navigation system independently developed and operated in China. The goal of system construction is to build an autonomous, open and compatible Beidou satellite navigation system with advanced technology, stability and reliability and global coverage. Beidou satellite navigation system consists of three parts: space segment, ground segment and user segment.