The development of editing satellite navigation and positioning technology has basically replaced the ground-based radio navigation, traditional geodetic and astronomical navigation and positioning technology, and promoted the new development of geodetic and navigation and positioning fields. Today, GNSS is not only a national security and economic infrastructure, but also an important symbol of modern great power status and national Comprehensive National Power. Because of its political, economic and military significance, the world's major military powers and economies are competing to develop independent satellite navigation systems. On 14 April 2007, our country successfully launched the first Beidou satellite, marking the beginning of the substantive operational phase of the fourth GNSS system in the world By 2020, the four GNSS systems, including GPS of the United States, GLONASS of Russia, Galileo of the European Union and Beidou navigation system, will be completed or modernized. In addition to the four global systems mentioned above, there are also regional systems and augmentation systems, among which are the QZSS in Japan and the IRNSS in India Enhanced systems include Waas in the United States, MSAS in Japan, EGNOS in the European Union, Gagan in India and NIG-GOMSAT-1 in Nigeria. In the next few years, the satellite navigation system will enter a completely new stage. Users will face the coexistence and compatibility of nearly 100 navigation satellites of the four major global systems. Rich navigation information can improve the availability, accuracy, completeness, reliability and reliability of satellite navigation users But at the same time, we have to face the competition of frequency resource, the competition of satellite navigation market, the competition of time and frequency dominance, compatibility and interoperability, etc. . Global Navigation Satellite System Global Navigation Satellite System ten anchors anchor point system introduction GPSGPS is a radio navigation and positioning system developed on the basis of the US Navy Navigation Satellite System. With all-round, global, all-weather, continuous and real-time navigation, positioning and timing functions, to provide users with precision three-dimensional coordinates, speed and time. Today, there are 31 working satellites in orbit, including 10 GPS-2A satellites, 12 GPS-2R satellites, and 9 modernized and improved GPS-2R-M and GPS-2F satellites with M Code Signals. In 2011, the United States pushed ahead with GPS upgrades, according to the GPS modernization program. GPS-2F satellite is the last type of the second-generation GPS to the third-generation GPS, which will further improve the positioning accuracy of GPS. With the development of science and technology, wireless communication technology and Global Positioning System technology are more and more applied to every aspect of daily life. No matter in all aspects of security monitoring and maintenance, Wireless Communication (GSM) and DGPS technology has played an important role. GSM based wireless communication networks covering a large area of data have been destroyed, easy to use, low cost. Separate GPS system, GSM system for vehicles and personnel via wireless satellite positioning communication link for mobile phone users to complete vehicle and personnel monitoring and sending location information 2 GLONASS is the second generation military satellite navigation system independently developed and controlled by the former Soviet Ministry of Defence, which is the second global satellite navigation system after GPS. The GLONASS system consists of a satellite, A GROUND-BASED TT & C Station and user equipment. The system consists of 21 working and 3 backup satellites and is distributed over three orbital planes, each with eight satellites and an orbital altitude of 19,000 km Run Time: 11 hours, 15 minutes. The GLONASS system was developed in the 1970s and the first satellite was launched into orbit in 1984. However, due to insufficient space funding, some of the satellites of the system were at one point aged, with only six satellites remaining in operation at the most serious, and in December 2003, the next-generation satellite, developed by the Russian Corporation for the scientific research and production of applied mechanics, was delivered to the Federal Space Agency and the Ministry of Defence on a trial basis in preparation for a full-scale update of Glonass in 2008. Technically, GLONASS system has better anti-jamming ability than GPS, but its single point positioning accuracy is not as good as GPS system. In 2004, India and Russia signed the long-term cooperation agreement on the peaceful use of the Russian Global Navigation Satellite System (GLONASS) , formally joining Glonass and planning to jointly launch 18 navigation satellites. The project began operating in 1976 and the entire system was up and running in 1995. Following the collapse of the Soviet Union, the GLONASS system was no longer viable and by April 2002 only eight satellites remained operational. After a 10-year period of paralysis of the GLONASS NAVIGATION CONSTELLATION, Russia resumed full-system operation at the end of 2011, following the planned resumption and modernization of Glonass following the economic recovery that began in August 2001. On 25 December 2006, Russia launched three GLONASS-M satellites on a proton-k carrier rocket, bringing the number of GLONASS satellites to 171. The Galileo is a global navigation and positioning system developed and established by the European Union. The Galileo programme was published by the European Commission in February 1992 and is jointly administered by ESA and the European Space Agency. The system consists of 30 satellites, of which 27 are operational and 3 are backup. The satellite has an orbital altitude of 23616 km and is located in three orbital planes with an inclination of 56. In October 2012, the Galileo launched a second batch of two satellites into space. The four official satellites already in space can form a network to provide initial ground accurate positioning. The Galileo system is the world's first civil based global navigation Global Positioning System. When it is operational, users around the world will be able to obtain more signals from navigation and positioning satellites using a multi mode receiver, which will significantly improve the accuracy of navigation and positioning. Beidou navigation system is a independently operated global satellite navigation system developed by China. The system is divided into two generations, the Beidou I and the Beidou II systems. In the 1980s, China decided to construct the bds, and in 2003, the Beidou Navigation Satellite Verification System was completed. The system consists of four geosynchronous orbit satellites, a ground control unit and a user terminal. There are three parts of errors in editing GPS by anchor point and anchor point factors: the first part is all GPS receivers, such as satellite clock error, ephemeris error, ionospheric error and tropospheric error, which can be completely eliminated by using the difference technique; the second part is propagation delay error, which can be mostly eliminated, mainly depending on the distance between reference receiver and User Receiver; the third part is the error inherent in all GPS receivers, such as channel delay, multipath effect and internal noise, which can not be eliminated;