Besides GPS and Beidou, what other satellite navigation systems are there in the world?

Satellite navigation system refers to a system that uses satellites to provide autonomous geo-spatial positioning. It allows small electronic receivers to transmit time signals along the line of sight through satellite radio and determine their positions (longitude, latitude and altitude/altitude) with high precision (several centimeters to several meters). The system can be used to provide position, navigate or track the position of an object with a receiver (satellite tracking). The signal also enables the receiver to calculate the current local time to a high accuracy and allows time synchronization.

At present, the most important satellite navigation systems in the world include: Global Positioning System (GPS) in the United States, Global Satellite Navigation System (GLONASS) in Russia, Beidou Satellite Navigation System (BDS) in China [and Galileo in the European Union]. Japan's Quasi-Zenith Satellite System (QZSS) and India's Regional Navigation Satellite System (IRNSS) are planned to be launched in 223.

GPS is the second generation satellite navigation system in the United States. It is developed on the basis of meridian satellite navigation system, and it adopts the successful experience of meridian system. The United States began to develop it in the 197s, which lasted for 2 years and cost 2 billion dollars. Finally, it was fully built in 1994, which is a new generation of satellite navigation and positioning system with all-round real-time three-dimensional navigation and positioning functions in the sea, land and air.

After nearly 2 years of practice, GPS has won the trust of surveying and mapping workers with its remarkable characteristics of all-weather, high precision, automation and high efficiency, and has been successfully applied to geodesy, engineering survey, aerial photogrammetry, vehicle navigation and control, crustal movement monitoring, engineering deformation monitoring, resource survey, geodynamics and other disciplines, thus bringing a profound impact to the field of surveying and mapping.

GLONASS is a satellite positioning system managed by the Russian Space Agency. At first, it took the former Soviet Union 2 years to launch 76 GLONASS satellites. However, unlike the GPS system in the United States, different satellites can be distinguished according to carrier frequency (GPS is code division multiple access (CDMA), and satellites can be distinguished according to modulation codes). The frequencies of the two carriers broadcast by each GLONASS satellite are L1=1,62+.5625k(MHz) and L2=1,246+.4375k(MHz) respectively.

By 1995, Russia had only completed the networking of 24 medium-high circular orbit satellites plus one spare satellite, costing more than 3 billion US dollars, and the satellite network was controlled by the Russian Ministry of Defense. The GLONASS space segment also consists of 24 satellites. Russia has adopted an open policy of military and civilian use and no encryption for GLONASS system. The positioning accuracy of GLONASS system is 16m horizontally and 25m vertically. Its application is far less popular than GPS. In the previous period, due to economic difficulties, the satellites in orbit were retired one after another. Now there are only six satellites available in orbit, so they can't be networked independently and can only be used in conjunction with GPS.

Galileo satellite navigation system is a global satellite navigation and positioning system developed and established by the European Union. Announced by Council of Europe in February 1999, Council of Europe and ESA are jointly responsible. The plan was first announced in 1999, with the aim of getting rid of Europe's dependence on the US GPS and breaking its monopoly. The project will launch 32 satellites with a total investment of 3.4 billion euros. The plan has been postponed several times because of differences among member States. The whole system consists of 3 satellites with an orbital height of 23616km, including 27 working satellites and 3 backup satellites. The orbit height of the satellite is about 24, kilometers, and it is located in three orbital planes with an inclination of 56 degrees.

Compared with American GPS system, Galileo system is more advanced and reliable. The satellite signals provided by American GPS to other countries can only find objects about 1 meters long on the ground, while Galileo's satellites can find targets about 1 meter long. It will not only make people's lives more convenient, but also bring considerable economic benefits to the industry and commerce of the European Union. More importantly, the EU will have its own global satellite navigation system from now on, which will help to break the monopoly position of American GPS navigation system, gain a favorable position in the global high-tech competition wave, and create conditions for building independent defense in Europe in the future.

Beidou satellite navigation system (BDS) is a global satellite navigation system developed by China. The system consists of three parts: space segment, ground segment and user segment. It can provide high-precision and high-reliability positioning, navigation and timing services for all kinds of users around the world, and has the ability of short message communication, and has initially possessed the ability of regional navigation, positioning and timing.

Beidou satellite navigation system consists of three parts: space segment, ground segment and user segment, which can provide high-precision and high-reliability positioning, navigation and time service for all kinds of users around the world. Moreover, it has the ability of short message communication, and has initially possessed the ability of regional navigation, positioning and timing. The positioning accuracy is decimeter and centimeter level, the speed measurement accuracy is .2m/s, and the timing accuracy is 1ns.

Quasi-zenith satellite system (QZSS), also known as Michibiki (), is a regional time transmission system with four satellites, and it is also a satellite-based enhanced system developed by the Japanese government. It mainly focuses on the functions of the global positioning system (GPS) operated by the United States in Asia-Oceania, with the emphasis on the goal of QZSS in Japan to provide high-precision and stable positioning services in Asia-Oceania, which is compatible with GPS systems.

The trial began on January 12th, 218, and was officially launched on November 1st. At present, it is also planned to establish a satellite navigation system independent of GPS in 223, with 7 satellites.

Indian regional navigation satellite system (IRNSS, NAVIC) is a free regional satellite navigation system developed by Indian Space Research Organization (ISRO). According to the design scheme, after the networking is completed with seven navigation satellites, it can provide accurate positioning, navigation and timing services for users within 15 kilometers around India and its borders.

Like the GPS system in the United States, IRNSS will provide two types of services in the future, namely standard services and restricted services. The former will be publicly available to all users, while the latter is an encryption service for authorized users. Perhaps one day in the future, our service choice of satellite navigation system will be as simple as installing home broadband now. ......