A GPS receiver device on earth receives these signals from the satellites and determines its
own location by:
Comparing its internal clock signal with the satellites.
This determines the distance from the satellites
location.
Through triangulation computation, the receiver
module calculates its own longitude and
latitude position. This is only possible when it
receives a minimum of three satellite signals.
In a sense, GPS can be compared to navigation methods used by sailing ship navigators
years ago. They used a sextant to plot the changing locations of known stars to determine
their own position. This, in conjunction with compass navigation, proved an accurate
method of sailing across the seas.
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On-Board Monitor and Navigation Systems