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Global positioning system (GPS), originally NAVSTAR GPS, is a satellite based radio navigation system owned by the U.S. government and operated by the U.S. air force. It is a global navigation satellite system that can provide geographic location and time information to GPS receivers on or near the earth, where four or more GPS satellites have unobstructed line of sight. Obstacles such as mountains and buildings block relatively weak GPS signals.

GPS does not require users to send any data, and it operates independently of any telephone or Internet reception, although these technologies can enhance the practicability of GPS positioning information. GPS provides key positioning functions for global military, civil and commercial users. The U.S. government created the system, maintained it, and made it freely accessible to anyone with a GPS receiver.

The GPS project was launched by the U.S. Department of defense in 1973 for use by the U.S. military, and put into full use in 1995. In the 1980s, the project was allowed for civilian use. Technological progress and new requirements for existing systems have led to efforts to modernize GPS and implement the next generation of GPS block IIIA satellites and the next generation of operation control system (OCX). These changes were triggered by a 1998 announcement by Vice President Al Gore and the White House. In 2000, Congress approved GPS III for modernization. In the 1990s, the U.S. government reduced the quality of GPS through a program called "selective availability," but that was no longer the case, and in May 2000, a law signed by President Bill Clinton terminated the quality of GPS. A new GPS receiver device with L5 frequency will be launched in 2018 and is expected to have higher accuracy and position the device within 30 cm or less.

The GPS system is provided by the U.S. government, which can selectively refuse to use it, as happened in the Indian Army during the 1999 Kargil war, or reduce the quality of service at any time. [8] As a result, many countries have developed or are in the process of establishing other global or regional navigation systems. Russia's global navigation satellite system (GLONASS) was developed synchronously with GPS, but its global coverage was still incomplete until the mid-2000s. GLONASS can be added to GPS devices to make more satellites available and to enable faster and more accurate positioning within two meters. China's Beidou navigation satellite system will reach a global scale by 2020. In addition, Galileo positioning system of EU and NAVIC of India. Japan's Quasi zenith satellite system (planned to start in November 2018) will be an enhanced system based on GPS satellites to improve the accuracy of GPS.