The Basics
A GPS receiver is simply a device that can locate itself
on Earth.
It does this by communicating with at least four satellites
in Earth's orbit.
For this reason, a GPS receiver is limited as to where
it can function.
It has to be able to "see" the satellites to calculate
latitude and longitude, which
means it usually won't work inside. So, one of
the basic characteristics of
GPS receivers is that they find your location only when
you are outside.
The simplest GPS receiver would give you just the coordinates
of your
location on Earth in latitude, longitude and altitude.
Latitude and longitude
are basically X and Y axes of a big imaginary grid wrapped
around the planet, and
coordinates, and you had a map of your area that used
this same coordinate
system, you could find your location simply by reading
the map. In this
view alone, a GPS reciever is an amazing device.
Without a GPS
receiver, you would have to find your position based
on the position of the stars
in the sky, using complicated tools and calculations.
And you wouldn't have
near the same level of accuracy.
Handheld GPS receivers give you much more than this raw
data. Even low-end
receivers have some sort of electronic map stored in
memory, so you don't have to carry
around a bunch of paper maps. The receiver takes the
coordinate information and applies
it to its electronic map, graphically pointing out to
you where you are in relation to roads, bodies
of water, etc. Maps vary a great deal in the level of
detail they offer; but the basic idea
behind this function is to give you a map that automatically
marks your location, without
you having to consider your coordinates. This is a great
convenience any time you need to
use a map, and is extremely helpful at times when you
can't take the time to find
your location on a map, such as when you're driving down
the highway.
For more information on the basics visit www.trimble.com/gps/