cheap car tracking device Navigation is a real-time navigation system, originally a research and development project of the US military, which can provide location navigation services for the military and the general public. After decades of progressive development, it has been able to cover the world and developed into the world's most advanced positioning and navigation system.

The system was initially composed of 5 to 8 satellites, and the number of satellites was very small, resulting in a small and incomplete coverage area, so the positioning accuracy was very low. Moreover, the height information at that time was not provided in this system, so the positioning accuracy was very unsatisfactory. Later, the original GPS plan was developed. The plan puts the satellites in three low-earth orbits at an Angle of 120 degrees, with an average of eight satellites orbiting each plane. Under this program, users on Earth will be able to observe signals from six to nine different satellites. However, due to financial constraints, the last revision was made in 1988. It was modified to have 21 working satellites and three spare satellites in six low-Earth orbits at an Angle of 60 degrees.

cheap car tracking device signals use code division multiple access modulation, so that all satellite signals can be in the same channel, and each satellite has its own special code. A broadcast-like form of information transmission, so it can be provided to an unlimited number of terminal services. As long as the user can receive the GPS signal, your device can enjoy positioning, timing and other related services. The GPS received signal is divided into military (P code) and civilian (C/A code) two codes, of which the military positioning measurement accuracy has reached the millimeter level, and the civilian has reached the 10m level.

cheap car tracking device system communication has two main points. First, it is broadcast communication, which can provide services to wireless devices. Second, establish a coordinate system with the center of the earth as the origin, collect the random code sent by the satellite, measure the position of the satellite and the observer through the delay, and calculate the position of the observer through the space distance intersection method. Theoretically, three satellites can get the position of the observer, but in reality, four satellites are used to eliminate errors.

The GPS receiver can be divided into two parts, the front-end signal receiver and the software processing. Because the GPS signal propagates to a very high frequency in space and is transmitted through the channel, the signal has been attenuated to a small amount and needs to be demodulated and amplified, which is the work of the front-end GPS receiver. The demodulated and amplified signals can be decoded and calculated by the software part to obtain the observer position.

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