Warning: your GPS coordinates may be wrong

Many people buy a GPS start it up and expect the UTM coordinates to be correct straight out of the box. This may not be the case. You need to make sure that you've set up your unit properly before leaving the trail and heading into the wilderness camping.

The most important thing to check is the map datum. This is the reference system the map creators use to put the numbers on the map. They are not all the same.

Older Lands Department maps in New South Wales in Australia used to be based on AUS66. This is about 200 meters different what you're GPS will be using by default. That can mean quite a lot when looking for that water source or moving through cloud or a blizzard. So read your map and change your GPS to be the same as your map.

Note that the new series of Australian maps are based on Australian geodetic datum 94. This probably isn't in your GPS. For our purposes it's close enough to WGS84 which is the base GPS system. See http://www.icsm.gov.au/icsm/gda/wgs84fact.pdf

If you're ever in doubt use WGS84.