The Colorado can determine elevation by satellite or barometer. If you don't know your exact elevation you can set the barometer altimeter by your satellite elevation. See this for more info.

Yep, it's a hassle to constantly recalibrate barometric altimeters from known elevations but they're a good gadget to have in many situations.
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If you only travel on sunny days you will never reach your destination.*

* May not apply at certain latitudes in Canada and elsewhere.