# Tag Info

If we want the usual GPS position error less than 10 m we should know the time needed by light or a microwave to cover this distance. The speed of light is $3 * 10^8 m/s$, so we need 33.3 nanoseconds for 10 m. To measure a distance, GPS measures the time needed by light for that distance. To be better than 10 m position error, the clock error should be less ...