The principle of GPS is simply to determine the target coordinates by navigation satellites, and then compare the map coordinates to determine the specific location of the target. The principle of GPS positioning is based on the instantaneous position of the satellite moving at high speed as the known starting data, and the method of spatial distance resection is used to determine the position of the point to be measured. The Global Positioning System (GPS) is a radio space positioning system that uses navigation satellites and ground stations to provide global, all-weather, high-precision, continuous, real-time three-dimensional coordinates (latitude, longitude, altitude), three-dimensional velocity and positioning information to any location on the surface of the Earth. Both can be used for positioning and navigation.
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The basic principle of GPS positioning
GPS positioning is based on the principle of satellite basic triangulation. The GPS receiver measures the distance of the radio signal to measure the distance of the satellite, and determines the position of the satellite in space. This is a high-orbit and precise positioning observation method. Assuming the satellite is at a height of 11,000 miles, measure our distance, first with a radius of 11,000 miles, draw a circle with the satellite as the center, and our position is on the sphere.
Let's assume that the second satellite is 12,000 miles away from us, and we are on the circumference where the two balls intersect. Now we are using the third satellite for precise positioning. Assuming a height of 13,000 miles, we can further narrow the range to the two-point position, but one of the points is not at our location and is very likely to be at a certain point in space. , we discard this reference point and choose another point as the position reference point.
If you want more accurate positioning, you must measure the fourth satellite. From the basic physics concept, the time multiplied by the signal transmission speed is the distance between us and the satellite. We measure the distance. Called the virtual distance, in the GPS measurement, we measured the wireless signal, the speed of light is almost 186,000 miles c, and the time is as short as amazing, even as long as 0.06 seconds, the time measurement needs two different Time meter, one time meter is installed on the satellite to record the time when the radio signal is transmitted, and the other time table is set on the receiver to record the time when the radio signal is received, although the time for the satellite to transmit the signal to the receiver is extremely short. But the time is not synchronized. Assuming that the satellite and the receiver are simultaneously making sounds to us, we will hear two different sounds. This is because the satellites are coming from 11,000 miles away, so there will be a delay. Therefore, we can delay the time of the receiver. From this delay time, the speed is the distance from the receiver to the satellite. This is the basic positioning principle of GPS.
It is assumed that the GPS receiver is placed on the ground to be measured at time t, and the time Î”t at which the GPS signal arrives at the receiver can be determined. Together with other data such as the satellite ephemeris received by the receiver, the following four equations can be determined:
The coordinates x, y, z and Vto of the points to be measured in the above four equations are unknown parameters, where di = c Î”ti (i = 1, 2, 3, 4).
Di (i = 1, 2, 3, 4) is the distance between satellite 1, satellite 2, satellite 3, satellite 4 and the receiver, respectively.
Î”ti (i=1, 2, 3, 4) are the times that the signals of satellite 1, satellite 2, satellite 3, and satellite 4 arrive at the receiver, respectively.
c is the propagation speed of the GPS signal (ie, the speed of light).
The meaning of each parameter in the four equations is as follows:
X, y, and z are spatial rectangular coordinates of the coordinates of the point to be measured.
Xi, yi, zi (i = 1, 2, 3, 4) are space rectangular coordinates of satellite 1, satellite 2, satellite 3, and satellite 4 at time t,
It can be obtained from satellite navigation messages.
Vt i (i = 1, 2, 3, 4) is the clock difference of the satellite clocks of satellite 1, satellite 2, satellite 3, and satellite 4, respectively, provided by the satellite ephemeris.
Vto is the clock difference of the receiver.
From the above four equations, the coordinates x, y, z of the point to be measured and the clock difference Vto of the receiver can be solved.
GPS application in personal positioning
China's first voice MMS GPS locator (what is GPS) -- reading the wholly-owned technology voice MMS GPS locator for the column, it has built-in national map data, no background support, combined with GPS global positioning system, GSM communication technology, Embedded voice broadcast technology, GIS technology, GIS search engine, image processing technology and image transmission technology, directly reply to the terminal Chinese address, MMS, or voice broadcast geographical location
GPS in the specific application of line vehicle management
The patrol vehicle monitoring and dispatching scheme serves a service-oriented enterprise or a management-type department that needs to monitor the state of the line through vehicle patrol. The scheme combines the planning of the line with the actual inspection work, taking the key points of the business as the core, and obtaining the position information of the vehicle through GPS real-time monitoring to investigate the completion of the patrol task of the vehicle, and the distance from each vehicle to the key point of the incident. The selection of the schedulable vehicle is automatically performed with the current state of the vehicle. Finally, combined with vehicle analysis and careful statistical reports, it can be planned, executable, and evaluable. The program was proposed by the successful practitioner 666GPS in the current industry, and successfully used in the 2010 Guangzhou Asian Games to China Telecom.
Application of GPS in Car Navigation and Traffic Management
3D navigation is the primary function of GPS. Aircraft, ships, ground vehicles and pedestrians can use GPS navigators for navigation. Car navigation system is a new technology developed on the basis of global positioning system GPS. The car navigation system consists of GPS navigation, autonomous navigation, microprocessor, vehicle speed sensor, gyro sensor, CD-ROM drive, and LCD display. The combination of GPS navigation system with electronic map, radio communication network and computer vehicle management information system can realize many functions such as vehicle tracking and traffic management.
GPS positioning system is not only used for navigation and positioning of missiles and spacecrafts, but also widely used for navigation and positioning of aircraft, automobiles and ships. It is used to establish monitoring, alarm and rescue systems for public security, banking, medical, firefighting, etc. Logistics management system, agriculture, forestry, environmental protection, resource survey, physical exploration, telecommunications, etc. are all inseparable from navigation and positioning, especially with the integration miniaturization of satellite navigation receivers, and various communication, computer and GPS integration Personal information terminals have made satellite navigation technology move from professional applications to mass applications, becoming the third new growth point of IT after communication and Internet. The satellite navigation and positioning application industry represented by GPS has attracted more and more people's attention.
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