Quote Originally Posted by OakLeaf View Post
In my experience mapmyride severely understates elevation gain, compared to any GPS in our riding groups, MotionBased, or SportTracks correction.

The ride I did on Saturday was 4100 feet according to my Garmin 705, 4400 feet according to another rider's 305, and I believe 1700 (maybe less) according to mapmyride. The rider with the 305 was of the opinion that his GPS understates elevation gain by about 10%. Unfortunately my data file got corrupted, so I wasn't able to upload it into SportTracks, which IMO is the most accurate of all.
I think all Map My Ride does is subtract the very lowest elevation from the very highest elevation and call that to total elevation. It doesn't actually add up the total climbing, which is what you really want. I did a century last year that had 7,000 feet of climbing according to the organizers, but Map My Ride said it was something like 1,500 feet of elevation gain. After doing it, I have to agree with the organizers -- that ride was ALL rollers, so it didn't actually have a huge difference in elevation, which is what I think MMR looked at, but it was endless climbing nevertheless.

I have a Garmin but have never figured out how to get total amount of climbing out of it, although I'm sure the numbers are there (I've never used SportTracks but now I look at it, I will definitely have to). Also, it seems really inaccurate on the % grade -- I've ridden up the same hill multiple times and had it tell me everything from 10% to 25% , so now if it's a big hill, I just check the elevation at the bottom and then at the top and subtract - not all that different from the OP's method of checking contour lines! Incidentally, I think the GPS is only guaranteed accurate to about 15 feet, a variation that can make a pretty huge difference in the reported % grade of a hill!