Introduced in the mid 1980's by the United States Dept of Defense (DOD) the GPS network has 24 Satellites which send out time information. Using a portable piece of equipment which received this information the equipment can then now where it is.
Over the last few years many GPS equipment has been used by the public but until May 2000 there was a small error included called the SA (Selective Availability). This was removed on the 1st of May 2000 which now means the GPS information is fairly actuate. There can be some problems which cause slightly errors such as in very wet bush or in a very tight valley.
Basically the GPS receives information from some of the satellites
around the world it can then provide information showing where you are,
speed, elevation etc depending on what model GPS you are using. Using a
GPS can be very good if going on a snow walk or ski, fog, Bushwalking and
even standard driving etc but should never replace maps, compass and knowledge
of how to use them.
New information regarding Grid-Refs used in these Bushwalking pages.
Importantly you need to specifically setup your GPS in regard to
what maps you wish to use. Most Topographic maps used list the Datum used
on the map, you need to match this on your GPS or Grid-Refs will be incorrect!
I have included the Datum information on the Maps
lists.
When going Bushwalking and using a GPS you should carry extra batteries for the GPS. I always carry 2 extra batteries for standard use and a extra 2 batteries only for emergency use. (Please note my GPS only has 2 Batteries in it but some other GPS's use 3, 4 or even 6 batteries.)