Originally Posted by
canklecat
Strava and some other activity apps reference existing databases for elevation, based on map data and data submitted by users who post data based on their computers and phones. Presumably these are reasonably accurate.
They are not. Strava still suffers from the inaccuracy of data that users upload.
Like this Strava segment, based on some very noisy user-uploaded data.
The actual grade is about 7%, but Strava says it's 12.3%. Strava says the KOM rider climbed it with a VAM of 2703 meters per hour, which is ridiculous.
Bad Strava segment
Here's what that segment would look like with "good" GPS data:
"good" Strava segment