Measuring vertical drop

The recent 12 hours of Snowbird gave me a good opportunity to reflect upon the accuracy of measurements used for computing a skier's total vertical. Until now, I had only relied upon a resort's official figures stating the vertical rise of each one of its lift, as opposed to checking an altimeter or GPS device reading.

Reality, however has showed me that what's stated by some mountain resorts is often inaccurate, inflated or rounded up; as an example, Snowbird claims 2,900 vertical for its tram when it's in fact 2,840. It would therefore seem logical to verify that public data. This makes a lot of sense, but it might be that the best way to check which altitude could be via static GPS reading or, more practically, by consulting Google Earth. Using a mobile GPS, especially when unloading a lift quite rapidly, might miss the top way point and induce false readings. A seemingly minute, but significant point...