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How is the maximum gradient calculated?

Tuesday 19 May
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Here's an example screenshot. The maximum gradient is showing as 3.4%, whereas the local gradient under my cursor is showing as 8.1%.

Where does the 3.4% figure come from?

Comments

Tue 19 May, 14:20

Apologies - the screenshot lost resolution in the upload. You'll have to take my word for it :)

Tue 19 May, 14:23

I think the best answer is that gradient calculation is remarkably complex and it’s something I’m still working on!

Tue 19 May, 14:32

Fair enough! Thought it might have been a bug. 

"It's complicated" is a completely valid answer.

Tue 19 May, 14:43

Essentially the problem is that raw elevation data for a route is always pretty jagged. If you just total up all the ups and downs from the data, then the total climb ends up being about 50% more than it really is, and the gradients are equally off-whack. So we have to do a fair bit of smoothing, including disregarding the smallest ‘climbs’ which are actually just undulations on the flat… and that isn’t really working to my satisfaction yet. It’s on the list. :)