HOW HIGH ARE YOU, REALLY?

摘要

If you recently bought yourself a new GPS, you may have noticed that the elevation reading is not very accurate. In fact, you may even suspect that the unit is defective if you happen to be floating around at sea level but the unit says you're collecting sea cucumbers at the bottom of the Marianas Trench. It seems that this is normal, and the experts at Garmin advise, "It is not uncommon for satellite heights to be off from map elevations by ±400 ft. Use these values with caution when navigating."