1. Positioning principle of Beidou system
The 35 satellites run around the earth at a height of more than 20,000 kilometers from the ground, surrounding the earth with a fixed cycle, so that at any time, any more than 4 satellites can be observed at any point on the ground.
Because the position of the satellite is accurate, in the observation of satellites, we can get the distance from the satellite to the receiver. Using the distance formula in the three -dimensional coordinates, the three satellites can be used to form three equations to solve the observation point of the observation point.Location (x, y, z).Considering the error between the clock of the satellite and the receiver clock, there are actually 4 unknown, the difference between X, Y, Z, and clocks, so the 4th satellite needs to be introduced to form 4 squares for solving, so as to obtain the observation point of the observation pointLavels and heights.
In fact, the receiver can often lock more than 4 satellites. At this time, the receiver can be distributed into several groups according to the satellite constellation, and each group is 4, and then the group with the smallest error is selected by the algorithm for positioning, thereby positioning, so asImprove accuracy.
The concept of "arrival time difference" (delay) is implemented: the accurate position of each satellite and the navigation information generated by the continuously sent atomic clock generated on the star of the star to obtain the time difference from the satellite to the receiver.
The satellite sends a radio signal with time and location information in the air for receiving the receiver.Due to the distance factor of the transmission, the time when the receiving machine receives the signal is delayed than the moment when the signal sends the signal, it is usually called a delay. Therefore, the distance can be determined by the delay.The satellite and receiving machine generate the same pseudo -random code at the same time. Once the two yards achieve time synchronization, the receiver can determine the delay; take the delay on the speed of light, and get the distance.
The computer and navigation information generators on each satellite understand their orbit position and system time very accurately, while the global monitoring station network maintains the position and system time of the satellite continuously tracking the satellite.Together with the main control station on the ground, with its operation control section, at least once a day, it is injected into the correction data of each satellite.Injecting data include: determination of the orbit position of each satellite in the constellation and the correction of the star clock.These correction data are calculated on the basis of complex models and can be maintained within a few weeks.
Satellite navigation system time is maintained by the pupae of the atomic clock on each satellite.Within a few seconds of NATO of these star clocks to the world coordination (UTC), UTC is maintained by the "main clock" of the US Navy's viewing table. The stability of each main clock is several 10^-13 seconds.The satellites used two frequency bands and two frequency bands in the early days. Later, it gradually changed to more frequent bands.Generally, within any designated time, only one frequency sign is working on each satellite.
Satellite navigation principle: The distance between satellite and users is based on the difference between the launch time of satellite signals and the time to reach the receiver, called pseudo -distance.In order to calculate the user's three -dimensional position and the bell deviation of the receiver, the pseudo -distance measurement requires that at least the signals from 4 satellites are received.
Due to the errors of satellite Running track and satellite clock, the effects of atmosphere on the signal on the flow layer and ionization layer on the signal, so that the positioning accuracy of civilian use is only tens of meters.In order to improve the positioning accuracy, the differential positioning technology (such as DGPS, DGNSS) is generally adopted, and the ground ground reference station (differential platform) is established for satellite observation., And released to the outside world.After receiving the correction number, the receiver compares it with its own observation value, eliminates most of the errors, and obtains a more accurate position.Experiments show that the positioning of differential positioning technology can be improved to the rice level.
Second, system function
(1) Four features
Shrology communication: Beidou system user terminal has two-way message communication functions, and users can transmit 40-60 Chinese characters at a time.It can reach information with 120 Chinese characters at a time.It has important application value in ocean navigation.
Precision time: Beidou system has a precision time-seeking function, which can provide users with 20ns-100ns time synchronization accuracy.
Positioning accuracy: horizontal accuracy of 100 meters (1S), 20 meters (similar to differential status) after the establishment of a school station.Working frequency: 2491.75MHz.
The largest number of users accommodated by the system: 540,000 households/h.
(2) military function
The military functions of the "Beidou" satellite navigation positioning system are similar to GPS, such as: positioning navigation of motion targets; the rapid positioning of the launch position of the weapon vehicle launch of the reaction time;
This function is used in military, which means that the positioning of troops at all Levels can be actively positioned, which means that once the troops at all Levels are equipped with the "Beidou" satellite navigation positioning system, in addition to their own positioning navigation, the senior headquarters can also pass at any time through at any time.The "Beidou" system masters the position of the troops and conveys the relevant commands, which is quite helpful for the implementation of the task.In other words, the execution of the "Beidou" satellite navigation positioning system can be used to command and control and the battlefield management.
(3) Civil function
1. Personal location service
When you enter a place where you are not familiar with, you can use a mobile phone or car satellite navigation device equipped with Beidou satellite navigation to receive chips to find the route you want to take.
2. Meteorological application
The development of Beidou navigation satellite weather can promote China's weather analysis and numerical weather forecast, climate change monitoring and prediction, and improve the level of spatial weather early warning business, and improve China's ability to prevent disaster prevention and mitigation.
In addition, the meteorological application of the Beidou navigation satellite system has an important impact on promoting the innovation application and industrial expansion of Beidou navigation satellite.
3. Road traffic management
Satellite navigation will help slow down traffic blockage and improve road traffic management level.By installing a satellite navigation receiver and data transmitter on the vehicle, the location information of the vehicle can be automatically reposted to the central station within a few seconds.These location information can be used for road traffic management.
4. smart transportation of railway
Satellite navigation will promote the upgrading and transformation of traditional transportation methods.For example, in the field of railway transportation, by installing satellite navigation terminal equipment, it can greatly shorten the interval between the train, reduce transportation costs, and effectively improve transportation efficiency.In the future, the Beidou satellite navigation system will provide highly reliable, high -precision positioning, speed measurement, and timing services to promote the modernization of railway transportation and realize the transformation of traditional scheduling to intelligent transportation management.
5. Sea transportation and water transportation
Sea transport and water transportation are one of the most widely transported methods in the world and one of the earliest applications for satellite navigation.Most of the various types of vessels driving in the world's oceans and rivers and lakes are installed with satellite navigation terminal equipment to make sea and water transport more efficient and secure.Beidou satellite navigation systems will provide navigation positioning and safety guarantee for water sailing ships under any weather conditions.At the same time, the telecommunications function unique to the Beidou satellite navigation system will support the development of various new services.
6. Air transportation
When the aircraft landed at the airport, the most basic requirement is to ensure the safe distance between the aircraft.Using the advantages of accurate positioning and speed measurement of satellite navigation, you can determine the instantaneous position of the aircraft in real time, effectively reduce the safe distance between the aircraft, and even in the case of heavy fog weather, it can achieve automatic blind drops, which greatly improves flight safety and airport operations.efficiency.By combining the effective combination of the Beidou satellite navigation system with the other systems, more security guarantees will be provided for aviation transportation.
7. Emergency rescue
Satellite navigation has been widely used in searches and rescue in the sparse areas of deserts, mountains, oceans, and other people.When major disasters such as earthquakes and floods, the key to the success of rescue is to understand the disaster in a timely manner and reach the rescue location quickly.In addition to the navigation positioning of the Beidou satellite navigation system, it also has a short newspaper communication function. Through satellite navigation terminal equipment, it can report the location and disaster situation in time to effectively shorten the time of rescue search, increase the time limit for rescue and disaster relief, and greatly reduce the loss of people's lives and property.
8. Guide to grazing
In October 2014, the Beidou system began to pilot the construction of the Beidou satellite grazing informatization guidance system in the pastoral area of Qinghai Province. It mainly relies on the automatic station of the data collection of Beidou smart terminals and pasture for the belligence of the pasture area to achieve data information transmission.The dynamic monitoring of the pasta, cattle, and cattle and sheep through Beidou ground stations and Beidou star groups and relay treated.In the summer of 2015, herders in pilot pastoral areas can use special Beidou smart terminal devices to guide grazing.
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