What is GPS?
The Global Positioning System (GPS) is a navigation system that uses a network of satellites to tell a user exactly where they are on the surface of the Earth. The full system uses about two dozen satellites arranged in orbits so that several are always in view from any place on Earth.
Key idea
Each satellite constantly sends out a radio signal that includes the time it was sent. A GPS receiver measures how long each signal takes to arrive, works out its distance from each satellite, and combines these distances to find its position.
How GPS finds a position
The signals travel at the speed of light, so a tiny time delay gives the distance to each satellite. The receiver needs signals from at least three satellites to fix a position on the ground, and a fourth to work out altitude as well. This method of combining distances is called trilateration. The result is given as a latitude and longitude — the exact position of the user.
Example
When a driver in Kuala Lumpur uses a navigation app such as Waze or Google Maps, the phone's GPS receiver picks up signals from several satellites and shows the car moving along the correct road in real time.
Uses of GPS
GPS is used all around us:
- Navigation in cars, phones and ships to find the best route.
- Tracking of delivery lorries and fishing boats so companies know where they are.
- Mapping and surveying land accurately.
- Precise timing for banks and communication networks that need clocks to agree exactly.
- Helping farmers and rescue teams to find exact locations quickly in the field.
Remember
A GPS receiver only listens for signals — it does not send anything to the satellites. It needs a clear view of the sky to receive the signals well.