What Is GPS and How Does It Work?

Everything you need to know about the Global Positioning System

All in-car navigation systems, driving apps, and mobile navigation apps like Google Maps all rely on GPS to get us from point A to point B. But what is GPS, and how does it work?

What Is the Global Positioning System?

The Global Positioning System (GPS) is a navigation system owned by the United States government that's made up of three main segments:

  • The Space Segment is a navigation system of at least 31 satellites, 24 (or more) of which are usually in flight and operational. These satellites fly within Earth's orbit at an altitude of 12,550 miles. Each individual satellite usually circles the Earth twice a day.
  • The Control Segment is an international network of control stations that track, monitor, and maintain the satellites in orbit. These control stations can also send data or commands to the satellites. The Control Segment is made up of 16 monitor stations, two Master Control Stations (one main one and one alternate), and 11 command and control antennas (four ground antennas and seven Air Force Satellite Control Network remote tracking stations).
  • The User Segment is for civilians and our GPS devices, also known as GPS receivers since they receive signals from the satellites in orbit to pinpoint our locations.
A person sitting in a car with a tablet uses a GPS location app.
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Who Invented GPS?

The four people usually credited with the invention of GPS are Ivan Getting, Bradford Parkinson, Roger L. Easton, and Gladys West. According to Lemelson-MIT, it was Getting who first envisioned GPS as we know it today as a concept involving the use of "a system of satellites to produce precise positioning data for rapidly moving objects such as missiles and airplanes."

Parkinson's contribution to GPS came in 1972, when he took on the lead role in directing the United States Department of Defense's GPS program. In this role, Parkinson was able to build upon Getting's original ideas. By 1978, Parkinson's GPS development project, known as the NAVSTAR GPS system, had been completed and accurate within three meters.

Roger L. Easton also contributed to the development of GPS and has been called the "father of GPS." Easton's contribution was the result of solving a problem related to tracking satellites. In an effort to synchronize the tracking stations' timing, Easton developed a time-based navigation system by placing clocks in satellites, allowing them to more accurately detect the exact location of users on the ground. Easton called this system "Timation," and the U.S. Department of Defense ended up incorporating its features into the development of the Global Positioning System.

Last but not least, mathematician Gladys West is also credited for her contribution to the development of GPS. West's contribution was her work in developing a model of the Earth that accounted for variations in the Earth's shape caused by gravity and other forces. West's Earth model is widely considered to be a foundational element of the GPS project.

How Does GPS Work and How Is It Managed?

The Global Positioning System relies on the relationship between GPS satellites and receivers on GPS-enabled devices. According to GPS technology company Garmin, a GPS technology company, the Global Positioning System works when GPS satellites transmit "a unique signal and orbital parameters that allow GPS devices to decode and compute the precise location of the satellite."

From this transmission, GPS devices are able to calculate the location of users by measuring the amount of time it takes to receive the signal. That calculation is then combined with the distance measurements from several other satellites. In order to correctly calculate a person's latitude and longitude, a GPS device needs to receive a signal from at least three satellites. Calculating altitude requires the signal of at least four satellites. Most GPS receiver devices will receive and track the signals of at least eight satellites, but this number can vary based on your location and what time it is.

According to GPS.gov, the Global Positioning System is maintained and operated by the U.S. Air Force. The U.S. Air Force "develops, maintains, and operates" the 24 satellites and control stations located throughout the world that make up the system.

Beyond Car GPS Systems: Everyday Uses for GPS

GPS isn't just for finding your way home. Other uses for GPS include:

  • GPS wearables, like GPS watches, can be used to keep track of children, pets, and the elderly.
  • GPS-controlled drones are used to film birds-eye-view shots in movies. GPS is also used in the film industry for location scouting.
  • Geocaching can be used to set up scavenger hunts by hiding items in certain locations, then uploading maps online to have other people search for them with GPS devices.
  • Your local power company may use GPS to track power outages.