GPS is the abbreviation of Global Positioning System. It was developed by the United States from the 1970s. It lasted for more than 20 years and cost 20 billion US dollars. It was built in 1994 and has a full range of sea, land and air. A new generation of satellite navigation and positioning system for real-time 3D navigation and positioning capabilities. GPS is mainly composed of three parts: the space part, the ground station part and the user part.
The space segment is a satellite network of 24 satellites covering the globe. These satellites are in a circular orbit about 20,000 km above the ground. The inclination of the orbital surface is 55 degrees. There are 6 orbits in the system, and 8 satellites are evenly distributed in each orbit. The satellites in the adjacent two orbits are separated by 30 degrees. The satellite attitude adopts a three-axis stabilization method to ensure that the radiation port of the navigation antenna on the satellite is always aligned with the ground. Here the carrier frequency of the satellite is the same: L1 band 1,575.42MHz, L2 band 1,227.6MHz. The satellite is equipped with a precision atomic clock with a stability of 1E-13. The atomic clocks of each satellite are synchronized with each other and synchronized with the atomic clock of the ground station group. This establishes a sophisticated time system for the GPS system, called GPS.
At present, the positioning accuracy provided by the GPS system is better than 10 meters, and in order to obtain higher positioning accuracy, differential GPS technology is usually adopted: a GPS receiver is placed on the reference station for observation. Based on the known precision coordinates of the base station, the distance correction from the base station to the satellite is calculated, and the data is transmitted by the base station in real time. While performing GPS observation, the user receiver also receives the correction number issued by the base station and corrects the positioning result to improve the positioning accuracy.
The positioning accuracy is in centimeters.
