Global Positioning System

The Global Positioning System (GPS), originally Navstar GPS,[2] is a satellite-based radio navigation system owned by the United States government and operated by the United States Space Force.[3] It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.[4] It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.[5]

Quick facts: Country/ies of origin, Operator(s), Type, Sta... ▼

Global Positioning System (GPS)

Logo
Country/ies of origin	United States
Operator(s)	US Space Force
Type	Military, civilian
Status	Operational
Coverage	Global
Accuracy	30–500 cm (0.98–16 ft)
Constellation size
Nominal satellites	24
Current usable satellites	38 (32 operational)
First launch	February 22, 1978; 45 years ago (1978-02-22)
Total launches	75
Orbital characteristics
Regime(s)	6 MEO planes
Orbital height	20,180 km (12,540 mi)
Other details
Cost	$12 billion[1] (initial constellation) $750 million per year[1] (operating cost)
Website	gps.gov

Geodesy
Fundamentals Geodesy Geodynamics Geomatics History
Concepts Geographical distance Geoid Figure of the Earth (radius and circumference) Geodetic coordinates Geodetic datum Geodesic Horizontal position representation Latitude / Longitude Map projection Reference ellipsoid Satellite geodesy Spatial reference system Spatial relations Vertical positions
Technologies Global Nav. Sat. Systems (GNSSs) Global Pos. System (GPS) GLONASS (Russia) BeiDou (BDS) (China) Galileo (Europe) NAVIC (India) Quasi-Zenith Sat. Sys. (QZSS) (Japan) Discrete Global Grid and Geocoding
Standards (history) NGVD 29 Sea Level Datum 1929 OSGB36 Ordnance Survey Great Britain 1936 SK-42 Systema Koordinat 1942 goda ED50 European Datum 1950 SAD69 South American Datum 1969 GRS 80 Geodetic Reference System 1980 ISO 6709 Geographic point coord. 1983 NAD 83 North American Datum 1983 WGS 84 World Geodetic System 1984 NAVD 88 N. American Vertical Datum 1988 ETRS89 European Terrestrial Ref. Sys. 1989 GCJ-02 Chinese obfuscated datum 2002 Geo URI Internet link to a point 2010 International Terrestrial Reference System Spatial Reference System Identifier (SRID) Universal Transverse Mercator (UTM)
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Artist's impression of GPS Block IIR satellite in Earth orbit

Civilian GPS receivers ("GPS navigation device") in a marine application

Automotive navigation system in a taxicab

An Air Force Space Command Senior Airman runs through a checklist during Global Positioning System satellite operations.

The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was launched in 1978 and the full constellation of 24 satellites became operational in 1993. Originally limited to use by the United States military, civilian use was allowed from the 1980s following an executive order from President Ronald Reagan after the Korean Air Lines Flight 007 disaster.[6] Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS and implement the next generation of GPS Block IIIA satellites and Next Generation Operational Control System (OCX).[7] which was authorized by the U.S. Congress in 2000.

From the early 1990s, GPS positional accuracy was degraded by the United States government by a program called Selective Availability, which could selectively degrade or deny access to the system at any time,[8] as happened to the Indian military in 1999 during the Kargil War. As a result, several countries — including Russia, China, India, Japan, and the European Union — have developed or are in the process of setting up other global or regional satellite navigation systems. However, Selective Availability was discontinued on May 1, 2000, in accordance with a bill signed into law by President Bill Clinton.[9]

When selective availability was lifted in 2000, GPS had about a five-meter (16 ft) accuracy. GPS receivers that use the L5 band have much higher accuracy, pinpointing to within 30 centimeters (12 in), while high-end users (typically engineering and land surveying applications) are able to have accuracy on several of the bandwidth signals to within two centimeters, and even sub-millimeter accuracy for long-term measurements.[9][10][11] Consumer devices, like smartphones, can be as accurate as to within 4.9 m (or better with assistive services like Wi-Fi positioning also enabled).[12] As of May 2021^[update], 16 GPS satellites are broadcasting L5 signals, and the signals are considered pre-operational, scheduled to reach 24 satellites by approximately 2027.