Technology · Signature experience
How does GPS figure out where you are?
GPS satellites broadcast their position and timing. A receiver measures signal travel time, converts it into distance, and combines several distance measurements to determine position.
Start the GPS positioning experienceSatellites broadcast signals
Signals include precise timing and satellite-position information.
Time becomes distance
Radio signals travel at the speed of light, so travel time can be converted to distance.
Several ranges are solved together
Four or more satellites are commonly used to solve 3D position and receiver clock offset.
Look for this first
Watch what changes during the experience
- 01How broad the possible region is with one satellite
- 02How each added satellite shrinks the overlap
- 03Signals traveling from satellites to the receiver
- 04How the location marker becomes fixed after enough signals
Why does it happen?
These ideas explain what you see
Satellites send time
GPS satellites broadcast their position and extremely precise timing information.
The receiver measures travel time
Signal travel time is used to estimate distance to each satellite.
Each distance is a sphere
All points at the same distance from one satellite form a large sphere.
Several spheres are solved together
Multiple ranges plus receiver clock offset are solved together to determine position.
Key words
Keep the hard words simple
- Trilateration
- Finding position from distances to known points rather than angles.
- Signal travel time
- How long the radio signal takes to reach the receiver.
- Receiver
- A phone, navigator, or other device that listens to GPS signals.
- Clock offset
- The small timing difference between the receiver clock and satellite time.
GPS satellites do not look down and tell your phone where it is. Your receiver listens to several satellites and computes the ranges itself.
Try it yourself
Add satellites yourself and toggle the range spheres
Replay the signal pulses, hide and reveal the range spheres, and rotate Earth to see how the possible location collapses.
Science sources