Page 1 of 1

Uncorrected elevation in Runalyze does not match the elevation data from imported fit file

Posted: Mon 17. Sep 2018, 22:55
by sfrunner1
I imported 3-4 months of fit files and all the elevation data is off typically a lot higher. I've since learned to disable the automatic elevation correction which typically adds more. I use a 920xt so I think the data I get is pretty good.

Here is an example of where the 920xt fit data was imported inaccurately which seems to be a bug. I'm linking to my garmin activity: https://connect.garmin.com/modern/activity/2732358752

I'll attach the fit file too.

The geonames.org (Aster) correction gets me closes to what appears in Garmin. But still almost 2k feet higher.

If I remove all correction, then I get 6,345 ft which is significantly higher than the 2,959 ft on Garmin. I've ran this course multiple times and it's very popular. The garmin data is close to accurate. But why wouldn't the fit file elevation data be the uncorrected amount in runalyze? Where is the 3k+ ft coming from? A bug?

Re: Uncorrected elevation in Runalyze does not match the elevation data from imported fit file

Posted: Tue 18. Sep 2018, 07:48
by mipapo
We use the profile to calculate the uphill/downhill meters:
https://help.runalyze.com/en/latest/cal ... nt-descent
So, it's no bug

Re: Uncorrected elevation in Runalyze does not match the elevation data from imported fit file

Posted: Wed 19. Sep 2018, 22:45
by th3oretiker
The Garmin data doesn't look very good. There are some errors (jumps of several hundred feet between km 25.7 and km 26.0). The big difference in elevation can be caused by different smoothing/filtering algorithms on these erroneous data.

Re: Uncorrected elevation in Runalyze does not match the elevation data from imported fit file

Posted: Sat 22. Sep 2018, 00:38
by sfrunner1
mipapo,
I appreciate the article and I have no fantasies that GPS is perfectly accurate. I'm not worried about that.

I am seeing this problem though across the board for my activities where there is an exaggeration especially ones with a larger length and elevation. Why not provide exactly what Garmin gives for uncorrected elevation? Obviously I do not understand the technical aspect of how that would work, so I apologize in advance if that does not make sense.

For the activity in question, Strava gives 2,792 ft. When I employ their elevation correction I get 2,989 ft.

Runalyze is not close. With any correction it's close to 2k ft more than Garmin and without it's over 3k ft more. That type of difference ends up being significant when you're doing 10k ft/wk or 40+k ft per month. Something seems amiss.

Runalyze I believe ends up exaggerating my vertical gain substantially over time so the value of the metric becomes unclear.

I'll add that this activity was a training run, so I ended up with over 20 people connected to my activity since they all ran the same course at relatively the same time. They were all using different devices and everyone one of their activities is around 3k ft or less. Again something seems to be amiss in how Runalyze is handling elevation gain.