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→GPS Receivers: clock synchronization
The most common use of GPS receivers is for automobile navigation, where devices from companies like Garmin and Tomtom are extremely popular. But these devices can also be used by people on foot, such as for hiking, orienteering, and geocaching. But, being complex electronic devices, their reliability is not as good as a plain old [[map]] and [[compass]].
The most common use of GPS receivers is for automobile navigation, where devices from companies like Garmin and Tomtom are extremely popular. But these devices can also be used by people on foot, such as for hiking, orienteering, and geocaching. But, being complex electronic devices, their reliability is not as good as a plain old [[map]] and [[compass]].
GPS receivers require that the clocks on the satellites be exquisitely well calibrated. The reason is that an error of 5 microseconds in the clock synchronization will lead to a position error of one mile. Achieving this accuracy requires that the clocks compensate for both the effects of [[special relativity]] (7 milliseconds per day) and [[general relativity]] (45 milliseconds per day in the opposite direction), leading to a total required correction of 38 milliseconds per day.<ref>http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html</ref>
==See also==
==See also==