How Does GPS Technology Work?

Satellites are behind this modern-day marvel

A rendering of the Navstar-2F satellite of the Global Positioning System
A rendering of the Navstar-2F satellite. Wikimedia Commons

The Global Positioning System (GPS) is made possible by a group of satellites in Earth's orbit. The constellation of satellites transmit precise signals, allowing GPS receivers on the ground to calculate and display location information to users. The GPS is owned by the United States.

By capturing the signals from satellites, GPS receivers are able to use the mathematical principle of trilateration to pinpoint geographic locations. With the addition of computing power and memory such as road maps, points of interest, and topographic information, GPS receivers are able to convert location, speed, and time information into a useful display format.

The Invention and Evolution of GPS

GPS was originally created by the United States Department of Defense (DoD) as a military application. The system has been active since the early 1980s but not become available to civilians until the late 1990s. Consumer GPS has since become a multi-billion dollar industry with a wide array of products, services, and internet-based utilities. As with most technologies, its development is ongoing; while it is a true modern marvel, engineers recognize its limitations and work continuously to overcome them.

GPS Pros and Cons

Capabilities
  • Works accurately in all weather conditions, around the clock, and around the globe.

  • No subscription fee to use GPS signals.

  • Generally accurate within 15 meters. Newer models with Wide Area Augmentation System (WAAS) signals are accurate within three meters.

Limitations
  • May be blocked by dense forest, canyon walls, skyscrapers, bridges, or walls, making accurate GPS navigation difficult.

  • Does not work well in indoor or underground spaces.

  • Satellite maintenance, radio interference, and solar storms can cause coverage gaps.

An International Effort

The U.S.-owned and -operated GPS is the world's most widely used space-based satellite navigation system. Russia's GLONASS satellite constellation also provides global satellite navigation service. Some consumer GPS devices use both systems to improve accuracy and increase the likelihood of capturing sufficient location data. 

Interesting Facts About GPS

The workings of GPS are a mystery to many of the people who use it every day. These points may surprise you:

  • Military GPS uses two frequencies, while civilian uses only one. This increases accuracy. Dual-frequency GPS devices are available to civilians, but their cost and size makes them impractical.
  • The U.S. government is engaged in an ongoing, multibillion-dollar improvement and modernization program.
  • U.S. taxpayers fund the world's GPS services, mostly through the Department of Defense. The 2017 budget was about $900 million.
  • An American joint civil/military body—the National Executive Committee for Space-Based Positioning, Navigation, and Timing—oversees the GPS. The U.S. Air Force maintains and operates it.
  • As of 2017, 24 GPS satellites circle the Earth.
  • GPS is essential to devices, conveniences, and services we take for granted every day, such as cell phones, watches, computers, weather forecasting, energy delivery, navigation, and emergency/disaster response.
  • Many industries rely on the accuracy of GPS, including banking, construction, aviation, shipping, and agriculture.
  • GPS is crucial to national security. All new military equipment is GPS-equipped.
  • GPS informs the world's air, sea, and road transportation systems.