Athens to Atlanta Roadskate (A2A Skate): Total Ascent, Elevation Gain; Barometric or GPS Data?

This is not scientific measurement, just a "thought-experiment," but depending on the consistency of the weather, barometric may be way better than GPS for measuring total ascent. If you don't care about the accuracy of the elevation but more the variance throughout several hours starting from a ballpark figure, barometric can be very accurate. If a weather front comes through, all bets are off, though. I have a record of one 11-hour period wherein I measured heart rate, including during sleep overnight, to find my resting or sleeping pulse. The total ascent for that sleeping and sitting around was only 79 feet. This must have been during a relatively constant weather period regarding barometric pressure, but still, that's not a bad error level it seems to me. As we've noted before with caloric measurements on the Garmin Forerunner 305 versus the Polar HRMs we have used, I will consider the the GPS-only elevation in the 305 as suspect until otherwise I learn better. My elevation measurements should be in feet on the Polar 720i, and those figures are closer to the MotionBased Gravity estimate than are most of the Forerunner estimates I saw online. I find the Forerunner 305 to be excellent at measuring XY (lat lon) and route distances (laps are amazingly consistent even with some tree cover in Greensboro Country Park). Speed measurements also seem great and the unit tracks well and has WAAS corrections. But I'm guessing the altitude measurements of the Forerunner 305 are not as good as the Garmin eTrex Vista I would think (at least in open skyview), since it uses barometric AND GPS data to adjust for weather drift to keep the figures a bit closer to honest. I wonder if anyone with an eTrex Vista (other than me!) has done the whole route and posted it on motionbased.com. I wonder if I still have the data from one or more A2A excursions or the time to dig it out? I wonder if DavidK is listening in? If I find time I'll try to look at altitude data from multiple workouts at GCP to see if those figures are consistent. What really matters to me is to be able to compare routes and workouts with some confidence that relative to each other, at least, the readings are consistent. As for better ways of measuring, of course there is the survey method with the tripod and post and all that, but it would take a long time to skate or walk the route and take measurements along the way. I'd say rest stops would be closed before getting to the first one! As it is, I may start wearing the Polar on the other wrist or hanging off a pack or bottle to get that data too! I hope not.