For those of you who track such things, which data do you "trust" the most? I went for a little 25 miler today and just uploaded from my Garmin Edge 305 and here's what various software programs come up with for elevation gain:

Garmin Training Center: 2099'
Ascent: 1748'
Garmin Connect (online): 1984' or 2887' with elevation correction enabled

I forgot what the unit actually said on the screen before I uploaded it (and elevation gain isn't kept in the history apparently), but I wouldn't be surprised if was yet another different number.

On the one hand, I'd think that the elevation correction enabled should be most accurate in this area since there ought to be plenty of real gps data for the software to use to put real numbers on the route. But it just seems way too much compared to the others and so I'd toss it out just because it's so far off.

So what's the deal with this stuff?

if it got cooler during the ride, its likely that the higher numbers are right.... if it got warmer on the ride, its likely that the lower numbers are right.

best advice: do it again and again and again and average it!

My experience with my 500 is that the elevation correct disabled is the most accurate, though the difference between it being enabled and disabled is usually very minor. I have no differences in elevation between training center and garmin connect.

I see big differences between the same Garmin file imported into Garmin Connect and MapMyRide, particularly in elevation gain and calories burned, but sometimes even the ride distance is different.

I see this too, but don't really mind. I mainly just log it into MMR so I can finish off the year of all my recorded rides so I have all of 2010 in one place. I use the garmin stuff to analyze now. MMR was cool until I got the Garmin, now the Garmin takes over all of the cool stuff from MMR.

Looking over Ascent's graph of the ride, i see the following notable climbs:

sea level to 666' (in 1.8 miles from my door, damn it!)
429' to 529'
478' to 610'
303' to 610'
428' to 518'
414' to 666'

That totals to about 1550', without including any elevation change lower than a 90' swing, and of course there are dozens of those on this kind of terrain. Adding in the major ones of those will get up to the 2000' numbers and then I suspect with the "correction enabled", they are including every single little change in elevation and that's why it's even 800' higher.

(This is basically the usual way out of town for me. I live at the beach and am surrounded by 700' to 1000' hills so first thing off the bat I have to climb. But I get to finish the ride with "the reward": from 666' back to sea level in a curvy 1.8 miles at 40mph+! Yippy!)