Your phone can seem to know exactly where you are, but GPS is not magic. It combines signals from satellites with other location technologies to estimate your position quickly and accurately.
How GPS works
GPS satellites continuously broadcast radio signals containing their location and the exact time the signal was sent. Your phone receives signals from several satellites and measures how long each signal took to arrive.
Because radio signals travel at a known speed, the phone can calculate its distance from each satellite. With signals from at least four satellites, it can determine your latitude, longitude, altitude, and the precise time.
Why your location can be so accurate
Your phone improves the satellite-based estimate with data from nearby mobile towers, Wi-Fi networks, Bluetooth devices, motion sensors, and digital maps. This is called assisted location, and it helps your phone find you faster, especially indoors or near tall buildings.
Is GPS always exact?
Not completely. Open outdoor areas may provide accuracy within a few meters, while buildings, tunnels, trees, weather conditions, and signal interference can reduce accuracy. Your phone usually combines multiple sources to choose the most reliable estimate.
What happens to your location data?
Apps can access your location only when you grant permission, although the exact options depend on your phone and operating system. You can review location permissions in your phone’s privacy settings and limit access to only when an app is in use.
So, your phone does not locate you from one signal alone. It compares information from satellites and nearby technologies, then uses mathematics to calculate the most likely position.