What is tablet GPS navigation?
GPS, the Global Positioning System, is a medium-distance circular orbit satellite positioning system that can provide Provides accurate positioning and high-precision time reference over most areas of the surface. The system is accomplished through 24 GPS satellites in space. At least 3 of these satellites are needed to quickly determine your position on the earth. The more satellites that can be received, the more accurate the decoded position will be.
GPS function
The global positioning system consists of three parts: (1) Ground control part, which is controlled by the main It consists of a control station (responsible for managing and coordinating the work of the entire ground control system), a ground antenna (under the control of the main control station, injecting message seeking messages into the satellite), a monitoring station (automatic data collection center) and a communication auxiliary system (data transmission). ; (2) The space part, consisting of 24 satellites, distributed on 6 planes; (3) The user device part, mainly composed of GPS receivers and satellite antennas.
The main features of the Global Positioning System: (1) All-weather; (2) Global coverage; (3) High-precision three-dimensional speed and timing; (4) Fast, time-saving and efficient: (5) Wide range of applications Function.
The main uses of the Global Positioning System: (1) Land applications, mainly including vehicle navigation, emergency response, atmospheric physics observation, geophysical resource exploration, engineering survey, deformation monitoring, crustal movement monitoring, municipal planning control etc.; (2) Marine applications, including determination of the best voyage route of ocean-going ships, real-time ship dispatching and navigation, marine rescue, marine treasure hunting, hydrogeological survey, marine platform positioning, sea level rise and fall monitoring, etc.; (3) Aerospace applications , including aircraft navigation, aerial remote sensing attitude control, low-orbit satellite orbit determination, missile guidance, aviation rescue and manned spacecraft protection detection, etc.
There are many types of GPS satellite receivers.According to the model, it is divided into geodesic type, total station type, timing type, handheld type and integrated type; according to the use, it is divided into vehicle-mounted type, ship-borne type, air-borne type, space-borne type and missile-borne type.
After more than 20 years of practice, the GPS system has been proven to be a high-precision, all-weather and global multi-functional system for radio navigation, positioning and timing. GPS technology has developed into an international high-tech industry with multiple fields, multiple modes, multiple uses, and multiple models.
GPS Principle
24 GPS satellites are at an altitude of 12,000 kilometers above the ground. It orbits the earth in a 12-hour cycle, so that at any time, more than 4 satellites can be observed simultaneously from any point on the ground.
Since the position of the satellite is accurately known, in GPS observations, we can get the distance from the satellite to the receiver. Using the distance formula in three-dimensional coordinates and using 3 satellites, we can form 3 equations and solve Get the location of the observation point (X, Y, Z). Considering the error between the satellite's clock and the receiver's clock, there are actually four unknowns, X, Y, Z and the clock error. Therefore, it is necessary to introduce a fourth satellite to form four equations to solve, so as to obtain the observation point Latitude, longitude and elevation.
In fact, the receiver can often lock more than 4 satellites. At this time, the receiver can be divided into several groups according to the satellite constellation distribution, each group has 4 satellites, and then the algorithm with the smallest error is selected. One set is used for positioning, thereby increasing accuracy.
Due to errors in satellite orbits and satellite clocks, the influence of the atmospheric troposphere and ionosphere on signals, and man-made SA protection policies, the positioning accuracy of civilian GPS is only 100 meters. In order to improve positioning accuracy, differential GPS (DGPS) technology is commonly used to establish a base station (differential station) for GPS observation. The known precise coordinates of the base station are used to compare with the observation values to obtain a correction factor and publish it to the outside world. . After the receiver receives the correction number, it compares it with its own observation value to eliminate most of the errors.Get a more accurate location. Experiments show that using differential GPS, the positioning accuracy can be improved to 5 meters.