How does a GPS receiver know what time it is?
The typical explanation of how GPS works has the receiver calculating the time-of-flight of the signals from several GPS satellites, and then determining the spheres around each satellite on which the receiver sits. To calculate he time of flight, it’s assumed the receiver compares the time at the receiver to the time stamp in each signal. For this to work, though, it seems to me that the receiver must know its time as accurately as the satellites know there’s. Since the receiver doesn’t have an atomic clock, however, it can’t. If it just uses the time from one of the satellites, it can’t use that satellite in the solution, increasing the number of satellites required for one. What’s really going on? Thanks.