GPS positioning technology

　　GPS positioning technology

　　GPS system can be said to be the earliest, most mature and most widely used positioning technology. The full English name of GPS is "Navigation Satellite Timing Ranging / Global Position System, that is, satellite timing and ranging navigation / global positioning system. The United States began to develop the GPS system in the 1970s, a 20-year, $20 billion project. The system was built in 1994. The system provides location information services by a constellation of 24 satellites located in space. These 24 satellites are evenly distributed on 6 orbital planes and revolve around the earth in a period of 11 hours and 58 minutes. The orbital inclination to the Earth's equatorial plane is 55°. The purpose of this layout is to ensure that at least 4 satellites can be observed at any point in the world and at any time.

　　The GPS system is a new generation of satellite navigation and positioning system capable of all-round real-time three-dimensional navigation and positioning in sea, land and air, and its positioning error can be controlled within 10m. After more than ten years of use in many professional departments around the world, GPS has obvious characteristics such as all-weather, high precision, automation, and high efficiency. Nowadays, the size of GPS client receivers is constantly shrinking, and the accuracy of the client is getting higher and higher, and it has even appeared in some high-end mobile phones, notebook computers and other electronic products. The popularization of GPS clients has accelerated the application of GPS positioning technology in the commercial field. While creating huge commercial profits, it is also gradually changing the way of life of modern human beings.

　　GPS mobile positioning technology

　　The United States Communications Commission (FCC) passed the Enhanced 911 Act in 1996 (amended again in 1999), requiring mobile phone operators to know the geographic location of each mobile phone (the error is controlled within 50~100m). Calling 911 for U.S. emergency services from any phone requires the government to know its location, even if the user doesn't know where they are. This FCC act has greatly promoted the development of mobile positioning technology and related service business research.

　　The arrival of the 3G era has opened a new chapter for the development of mobile positioning technology. With the improvement of data transmission capability, the popularization of terminal multimedia capabilities and the emergence of built-in GPS solutions in terminal chips, there are fewer and fewer restrictions on mobile positioning technology. At present, there are four main types of 3G mobile positioning technologies commonly used around the world, namely, network-based CELL-ID, TOA/TDOA positioning technology, terminal-based OTDOA positioning technology, and A-GPS positioning technology mixed with network and terminal.

　　The rapid development of mobile positioning technology and the rapid growth of the number of global mobile users have also provided unprecedented development opportunities and extremely attractive market prospects for the location-based service (LBS) of users.