How GPS navigation works

In short: A GPS receiver calculates its position by measuring the travel time of radio signals from at least four satellites. The navigation app places this position on a map and works out the route.

In more detail: Each satellite sends its position and the exact time. The differences in travel time give distances that fix the location.

In detail

• Four satellites: Three for the position in space, the fourth corrects the receiver’s clock.
• Systems: GPS (USA), Galileo (EU), GLONASS (Russia), BeiDou (China). Modern phones use several.
• Accuracy: About 3 to 10 metres, worse in cities and tunnels.
• Route calculation: The app searches a road graph for the fastest path, for example with the Dijkstra or A* algorithm (suchverfahren-und-planung-a-und-monte-carlo-baumsuche).
• Traffic data: Anonymous location data from many devices shows jams in real time.
• Privacy: Location history can be switched off in the settings.