I haven't had a real use for GPS, but am thinking of getting one for some informal elevation surveys - stand on a doorstep at potential shelter X, find out its elevation, compare it to expected river elevation. Not so critical where I am, just to know how high I am above sea / river level several miles away from the river. Would any of these models be more accurate in terms of measuring elevation? +/- 3-6 feet could be a big deal here.