How Does GPS Know Your Location? A Simple Interactive Explanation
GPS satellites broadcast their position and precise time. A receiver measures how long several signals took to arrive, converts those times into distances and combines them using trilateration.
What satellites send
A GPS satellite broadcasts a one-way radio signal containing its location and precise time. It does not receive your location or choose where you are.
Time becomes distance
Radio signals travel at the speed of light. Comparing the transmitted time with the arrival time lets the receiver estimate how far away each satellite is.
Why several satellites matter
One distance leaves many possible positions. Several overlapping distances reveal a location, while an additional signal helps correct the receiver’s clock. Phones may also combine GPS with Wi-Fi and mobile-network information.
Common questions
Does GPS need the internet?
The satellite-positioning calculation itself does not require mobile data, although phones often use the internet to download maps and obtain assistance information faster.
Is GPS triangulation or trilateration?
GPS positioning is based on trilateration because it uses measured distances, not observed angles.
Why can GPS be inaccurate indoors?
Roofs and walls can weaken, block or reflect satellite signals, making their travel times harder to measure accurately.