Why am I getting different data on Garmin Connect vs. GTC?

[berkeley]

Interesting. Thanks.

So here's maillotoplis' quote from one of those threads "It's not really a Garmin issue, because the barometric adjusted Garmin data run through Garmin training center is pretty spot on - consistent with my old HAC4 data for the same rides and with other people's Polars, etc. "

But my GTC numbers seemed WAY off - so yeah, I'm confused.

So, not wanting to rehash this clearly long-running debate, has anyone found that the Garmin Connect is particularly problematic? From what I can tell, it's more accurate than the GTC, but that's a guess on what I thought I did yesterday. It seems that others have found GTC to be accurate, but I can't seem to find anyone using garmin connect or commenting on the elevation accuracy.

My 305 is the Edge, if that makes any difference.

Off to google again...

[TrekTheKaty]

There was a discussion here last summer about the accuracy of elevation on a Garmin 305. The consensus was the elevation is inaccurate with this device--I forget why. However, if the numbers looks impressive--I say they are correct

I use a Garmin 305 with MotionBased. I have a Mac and could only use the Garmin software when it was updated recently. I downloaded some old rides and the numbers were slightly different. When I compare distance and speed with two other riders using different brands of bike computers--it is very accurate.

Motionbased does have a very active and informative forum--it was purchased by Garmin.

[OakLeaf]

My 305 is the Edge, if that makes any difference.

Yes, it does, actually.

The Edge 305 has a barometric altimeter. The Forerunner series, including the Forerunner 305, does not.

[SadieKate]

Some searches from the world wide web:
http://forums.bicycling.com/eve/foru...7/m/3731042216

http://cyclingexperiences.com/2009/0...t-update-0302/

Examples with a non-barometric device
http://gpsrunner.blogspot.com/2009/0...orrection.html
http://getsatisfaction.com/garmin/to...a_doesnt_match

Quote from Garmin at some point in time (Iforget when):
Garmin Connect is using a different methodology to smooth elevation gain/loss compared to MotionBased. As a result, especially for Forerunner devices, the elevation gain/loss numbers will be inflated. We are still working on our smoothing algorithm and intend to run this across all activities at Garmin Connect in the future to more accurately reflect the actual gain/loss.
Garmin Connect does not support weather at this time. We plan on introducing this feature at Garmin Connect. When we do, it will run against all past, present, and future activities at Garmin Connect.

I lurves me Sporttracks.