Beidou Global Constellation Completed _ Beidou Global Constellation Deployment Completed

What can China Beidou global satellite navigation system constellation play after deployment?

I. Industrial and regional applications

Since Beidou system provided services, it has been widely used in transportation, agriculture, forestry and fishery, hydrological monitoring, weather forecasting, communication system, power dispatching, disaster relief and public safety. , and has been integrated into the national core infrastructure, resulting in significant economic and social benefits. ?

1, transportation, Beidou system is widely used in key transportation process monitoring, highway infrastructure safety monitoring, port high-precision real-time positioning scheduling monitoring and other fields.

By the end of 20 18 and 12, Beidou system had been applied to more than 6 million operating vehicles, 30,000 postal and express vehicles, about 80,000 buses, more than 3,200 inland navigation facilities and more than 2,900 maritime navigation facilities in 36 central cities, and the world's largest dynamic monitoring system for operating vehicles had been built, which effectively improved the monitoring management efficiency and road transportation safety level.

According to statistics, compared with 20 17 and 20 1 1, the number of serious accidents, deaths and missing persons in national road transport decreased by 50%.

2. In the field of agriculture, forestry and fishery, the agricultural machinery operation supervision platform based on Beidou has realized the remote management and accurate operation of agricultural machinery, served more than 50,000 agricultural machinery and equipment, increased the precision agricultural output by 5%, and saved the oil consumption of agricultural machinery by 10%.

Positioning and short message communication functions have played a prominent role in forest fire prevention and other applications. Provide services such as ship position monitoring, emergency rescue, information release and fishing boat entry and exit management for fishery management departments. More than 70,000 fishing boats and law enforcement vessels across the country have installed the Beidou terminal, and more than 6,543,800 people have been rescued.

3. Hydrological monitoring has been successfully applied to the real-time transmission of hydrological forecasting information in mountainous areas, which improves the accuracy of disaster forecasting and provides important support for formulating flood control and drought relief dispatching schemes.

4. In the aspect of meteorological forecast, a series of Beidou terminal equipment for meteorological forecast have been developed, and a system application solution has been formed, which has improved the observation accuracy, automation level and emergency observation ability of domestic high-altitude meteorological detection systems.

5. In the communication system, the key technologies such as optical fiber stretching have been broken through, and an integrated satellite time service system has been developed, and the Beidou bidirectional time service application has been carried out.

6. In power dispatching, the application of power time synchronization based on Beidou has created conditions for high-precision time applications such as power accident analysis, power early warning system and protection system.

7. In disaster relief, based on the navigation, positioning and short message communication functions of Beidou system, it provides real-time disaster relief command and dispatch, emergency communication, rapid reporting and sharing of disaster information and other services, which significantly improves the rapid response ability and decision-making ability of disaster emergency rescue.

8. In terms of public safety, more than 400,000 police terminals across the country are connected to the police location service platform. Beidou system has played an important role in the security of Asia-Pacific Economic Cooperation (APEC) meetings, G20 summits and other major events.

Second, large-scale application.

The public service of Beidou system has broad development prospects. Navigation service based on Beidou has been adopted by e-commerce, mobile intelligent terminal manufacturing, location services and other manufacturers, and has widely entered the fields of mass consumption, sharing economy and people's livelihood in China, profoundly changing people's production and lifestyle. ?

19, 10 in may, the "5G+ Beidou high-precision positioning open laboratory" jointly established by China Unicom and Huada Beidou brought together operators, chip module vendors, equipment vendors, vertical industry applications, research institutions and universities to build a cooperative ecology based on 5G and Beidou, and jointly promote the application of 5G+ Beidou high-precision positioning in vertical industries. ?

1. In the field of e-commerce, the logistics trucks and distributors of many domestic e-commerce enterprises have realized real-time dispatching of vehicle, people and goods information by using Beidou vehicle terminal and bracelet.

2. In the field of smart phone applications, mainstream chip manufacturers at home and abroad have introduced integrated chips compatible with Beidou. In the first three quarters of 20 18, about 470 smartphones sold in China market had positioning function, of which 298 models supported Beidou positioning, and the positioning support rate of Beidou reached over 63%.

3. In the field of smart wear, a variety of smart wearable devices such as watches and bracelets supporting Beidou system, as well as special crowd care products such as student cards and old-age cards are constantly emerging and widely used.

principle

1, spatial positioning principle

If the spatial positions of three points A, B and C have been determined in space, and the distances from the fourth point D to the above three points are all known, the spatial position of D can be determined. The principle is as follows:

Because the position of point A and the distance between AD are known, it can be inferred that point D must be located on a sphere with a center and AD as a radius. According to this method, two other spheres with centers B and C can be obtained, that is, point D must be located at the intersection of the three spheres, that is, the intersection of the three spheres. The positioning of Beidou's test system and formal system depends on this principle.

2. Active and passive positioning

When the satellite navigation system adopts active time ranging and positioning, the user terminal sends a signal to the ground control center through the navigation satellite for positioning, and then the ground control center sends a ranging signal to obtain the distance between the user and the two satellites according to the signal transmission time.

In addition to this information, the ground control center also has a database, which is the distance from each point on the earth's surface to the center of the earth sphere. When it is determined that the user is also on the uneven sphere, and the conditions for the intersection and positioning of the three spheres have all been met, the control center can calculate the user's position and send the information to the user terminal. Beidou's experimental system is completely based on this technology, and the subsequent Beidou satellite navigation system not only adopts new technology, but also retains this technology.

When the satellite navigation system adopts passive time ranging technology, users receive signals from at least four navigation satellites, and distance information can be obtained according to time information. According to the principle that three spheres intersect, the user terminal can calculate its spatial position by itself. This is the technology used by GPS, and Beidou satellite navigation system also uses this technology to realize global satellite positioning.

2. Accuracy (sex)

Referring to the principle of three-ball rendezvous and positioning, according to the distance information from three satellites to the user terminal and the three-dimensional distance formula, the position information of the user terminal can be obtained by listing three equations, that is, in theory, passive positioning can be realized by using three satellites, but there is generally an error between the satellite clock and the clock used by the user terminal;

Electromagnetic waves travel at the speed of light, and a small time error will cause great distortion of distance information. In fact, we should think that the clock difference is not 0 but an unknown number T, so there are four unknowns in the equation, namely the three-dimensional coordinates (x, y, z) of the client and the clock difference T, so it takes four satellites to list four equations about distance.

Finally, we can get the answer, that is, the three-dimensional position of the client, which can be further converted into latitude and longitude and altitude.

If there are enough satellites in the air, the user terminal can receive the information of more than four satellites, and the four satellites in each group can be divided into multiple groups, and multiple groups of equations can be listed, and then the group with the smallest error can be selected through a certain algorithm, which can improve the accuracy.

Electromagnetic waves travel at a speed of 300,000 km/s. When measuring the satellite distance, if the satellite clock has a time error of one nanosecond (one billionth of a second), it will produce a distance error of 30 cm. Although the satellite uses a very accurate atomic clock, it will accumulate great errors;

Therefore, the ground workstation will monitor the satellite clock and compare the result with the larger and more accurate atomic clock on the ground to get the error correction information, and the end user can get the more accurate information after correction through the receiver. At present, the typical satellite atomic clock has accumulated several nanoseconds of error, resulting in a distance error of about one meter.

In order to improve the positioning accuracy, differential technology can also be used. A reference station is set up on the ground, and its known precise coordinates are compared with those given by the navigation system, so that a correction number can be obtained and released. Using this correction number, the user terminal can correct its own navigation system calculation results again, thus improving the accuracy.

For example, after using differential GPS, the positioning accuracy can reach about 5 meters.

Refer to the above? Baidu Encyclopedia-Beidou Satellite Navigation System