> You will be disappointed in the GPS's ability to determine altitude.
> However, a good topo program (that handles proprietary topo data) will
> show you an accurate altitude at every spot on the map, so you can know
> your altitude from that.

My eTrex Vista from Garmin has two altimeters.  One via GPS and another via
barometric pressure.  Seems accurate within the indicated range (less than
50 feet almost always, 18 feet regularly).  I leave the unit on my dash, or
use it's optional handlebar mount on my bicycles.

Use  http://www.expertgps.com/ to add waypoints before a trip, and to view
tracks on the return.  Nearly any image can be calibrated for use as a map.
If you have Internet available, the program will snatch up topo or satellite
maps for you as needed - in the USA anyway.

I never leave home without it.

Dan Brideau
http://www.skidweeb.com/