when gp be first introduce we use to joke about the inaccuracy of they satellite determine elevation . I buy the Vista cx because I think the built-in barometric altimeter would reduce the problem with satellite determine elevation - it do not . the expect error in elevation be 50 to 200 foot , far worse than the positional accuracy of the gp . to reduce error Garmin recommend calibrate the unit every hour to a known elevation - if you know the elevation that well you do not need a gp ! so , while you marvel at the positional accuracy of the unit you can still expect to get a good laugh from the elevation .