How does GPS work?
Quick Answer
GPS uses a constellation of 24+ satellites that each broadcast precise time signals. Your device calculates its distance from at least 4 satellites via signal travel time, determining your position to within 1 meter.
The Full Story
The Global Positioning System (GPS) works through a constellation of at least 24 operational satellites (currently 31) orbiting at about 20,200 km altitude. Each satellite broadcasts its position and a precise timestamp from onboard atomic clocks accurate to within nanoseconds. Your GPS receiver picks up signals from multiple satellites and calculates the time each signal took to arrive. Since signals travel at the speed of light (299,792 km/s), the receiver can compute its distance from each satellite. With signals from at least 4 satellites, it uses trilateration to pinpoint its 3D position (latitude, longitude, altitude). Modern GPS is accurate to within 30 cm for military use and about 1–3 meters for civilian use. Einstein's relativity is essential to GPS: without relativistic corrections (satellites's clocks run 38 microseconds fast per day due to weaker gravity), positions would drift by ~10 km daily.
Key Facts
YouTube Angle
Suggested video title for this topic:
"How GPS Actually Works — Atomic Clocks, Satellites & Einstein"