Global Satellite Navigation System (GNSS); It is a general term used to describe a system that uses satellite signals to determine the position of a user's receiver. Currently, the GPS system in the United States and the GLONASS system in Russia are fully operational and can provide global positioning services. In addition, China's Beidou system (also known as Compass) and the European Union's Galileo system are in the process of deployment Among the four global navigation systems mentioned above, GPS is the oldest system and has been providing global positioning services since 1994. The GPS system is also constantly being upgraded and updated to provide more signals and more accurate positioning services. In 2012, the Block IIF satellite of the system was officially put into use, and the Block III satellite is also under planning. The GLONASS system first began during the former Soviet Union period in 1982 and was temporarily stagnant due to the disintegration of the Soviet Union. In recent years, Russia has restarted and completed the system. The GLONASS system was officially launched in October 2011, providing global positioning services. Russia continues to update and upgrade its system by using new GLONASS-K satellites to transmit signals similar to GPS and Galileo The other two systems - Galileo and Beidou - are currently in the deployment process. The Galileo system was developed by the European Union and the European Space Agency. In 2005 and 2008, two experimental satellites were launched, and in 2011 and 2012, four in orbit verification satellites were launched. The Galileo system is scheduled to provide initial services in 2015, and the entire system is expected to be deployed and completed in 2020 The Beidou system began providing limited initial services in December 2011 and was officially announced in September 2012. At the beginning of its announcement, the Beidou space segment included 15 satellites, providing regional positioning services to the Asia Pacific region. The entire system is planned to be completed by 2020. Due to the fact that the Chinese government did not release the Interface Control Document (ICD) until December 2012, the development of products related to the Beidou system has also been restricted. Now that ICD has been released, the development of Beidou products is expected to achieve rapid growth In addition to the four satellite navigation systems mentioned above, there are also some other related satellite systems. One type is Satellite Based Augmentation System (SBAS), which uses geostationary satellites to transmit correction and integrity data to existing global satellite navigation systems, thereby improving the positioning accuracy of GNSS receivers. Satellite based augmentation systems include the Wide Area Augmentation System (WAAS) in North America, the Geosynchronous Orbital Coverage Service (EGNOS) in Europe, the Multi functional Satellite Based Augmentation System (MSAS) in Japan, and the GPS and GEO Enhanced Navigation System (GAGAN) in India. Another type is the Regional Satellite Navigation System (RNSS), which increases the coverage of satellites in specific areas by launching satellites that only operate over them, thereby increasing the number of visible stars. Regional satellite navigation systems include Japan's quasi zenith satellite system (QZSS) and India's regional navigation satellite system (IRNSS). At present, the first QZSS satellite has been put into use, and equipment supporting the satellite has been launched. The IRNSS system is still in the development stage and is expected to include three geostationary satellites and four geostationary satellites