By Kevan Gregalis, Sam Yellen, and William Cahoon
This physics project was written for
a Physics 24 class, Section 001
at the University of North Carolina at Chapel Hill
December 1, 2000
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Project Assignment
Introduction
The global positioning system, or GPS, is a network of
24 earth-orbiting
satellites. These satellites allow anyone who owns
a GPS receiver to
determine his position (precise latitude, longitude,
and altitude) anywhere
on the planet. There is a great deal of physics
involved in the use of this
system in determing exactly where you are on Earth.
A standard
GPS receiver will not only place you on a map at any
particular location,
but will also trace your path across a map as you move.
If a GPS receiver is
left on, it will stay in constant contact with the network
of earth-orbiting
satellites.
Trilateration
Trilateration is the basic geometric principle that allows
a person to find
a location if its distance from other, already known
locations is known.
The GPS receiver finds its distance from four or more
GPS satellites.
Once the receiver determines its distance from the GPS
satellites, it can
calculate its exact altitude and location on Earth.
If only three GPS satellites
are available, then the GPS can give location information
but not altitude.
Physics Behind GPS