Thanks for the info.. So does a Garmin basically just self-calibrate when it's turned on? ie. baseline from start of the ride barometric reading? If so, would turning off and on the unit and creating separate smaller "activities" help? Obviously not ideal.

As to temperature effects, this theoretically could be easily corrected for by the unit, which also has a built-in thermometer, no?

I played with Strava's elevation correction.. it would generally remove about 10% of elevation to rides i tried it on.. Annoyingly, once you apply elevation correction in Strava, I found out you can't revert (unclick) to the Edge's originally reported elevation. I presume you'd have to resend or resync the data from Garmin again.