www.rambler-info.org.uk - links to GPS information sites
This site is the best jumping-off place for GPS information. They have a massive list of links to a wide range of other sites. They also have their own reviews and information and some guest writers on the site.
Click for Joe Mehaffey, Jack Yeazel, Dale DePriest's site
A general forum for discussion. Operated by the same three authors as above.
Peter H. Dana is at the Department of Geography, University of Texas at Austin. He has written a massive collection of information about mapping systems in general. This is the site you need to understand the lists of datums and co-ordinates on your GPS. [Co-ordinates are listed as "Units" on the eTrex setup menu]
This is heavy stuff, but a good background for those using their GPS units on a world-wide range of maps. If you are ignorant about such things, you could find you have disagreements between maps and GPS which range up to hundreds of metres in difficult cases.
Geodetic Datums
Map Projections
Co-ordinate systems
Some notes on the GPS system
In his notes you will find definitions of UTM and UPS.
