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Replace GraphHopper elevation gain with more accurate value
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Description

As mentioned in T48#3784, elevation gain value displayed on "Draw my route" (computed by GraphHopper API) and the value displayed on ride detail page (computed ourselves) are different, and can cause confusion. This task is about showing the same value consistently, using our own value which is more accurate.

There are some technical challenges in displaying our value interactively, as it requires some time to calculate, up to few seconds for long rides. Value from GraphHopper is inaccurate (exaggerated), but available very fast.

Another possible approach is to rewrite our smoothing code (Python, server side) into JavaScript and have client calculate the smoothing.

Event Timeline

francois created this task.Jun 28 2016, 6:07 PM
francois renamed this task from Replace GraphHopper elevation gain value with ours to Replace GraphHopper elevation gain value with our more accurate value.
francois mentioned this in Unknown Object (Maniphest Task).
jose moved this task from Restricted Project Column to Restricted Project Column on the Unknown Object (Project) board.Jul 30 2016, 9:01 PM
jose moved this task from Restricted Project Column to Restricted Project Column on the Unknown Object (Project) board.
francois updated the task description. (Show Details)Aug 24 2016, 9:47 AM
francois raised the priority of this task from Normal to High.Aug 24 2016, 9:53 AM

FYI, GraphHopper is aware of the inaccurate elevation gain values they calculate, and also have a bug entry for fixing it: https://github.com/graphhopper/graphhopper/issues/517

francois added a subscriber: rahul.EditedAug 24 2016, 10:29 AM

Rahul showed an example where the GraphHopper value shows significant discrepancy: 2300 vs 4300

this is a critical error and can seriously damage the credibility of our mapping interface

I agree we should not display elevation gain on "Draw my route on map" until this task is addressed. I removed elevation gain there,

I know, as Jose mentioned, there is still some use to show inaccurate value: we can see a variation of the elevation gain when moving points. I think the disadvantages are more important.

francois updated the task description. (Show Details)Aug 25 2016, 2:41 PM
francois added a project: Unknown Object (Project).Sep 25 2016, 11:24 PM
francois mentioned this in Unknown Object (Maniphest Task).Dec 31 2016, 12:26 AM
jose moved this task from Restricted Project Column to Restricted Project Column on the Unknown Object (Project) board.Jun 2 2017, 7:41 PM
jose mentioned this in Unknown Object (Maniphest Task).Feb 2 2018, 6:57 PM
francois shifted this object from the Restricted Space space to the S6 Public space.May 6 2018, 10:46 PM
francois changed the visibility from "All Users" to "Public (No Login Required)".

Another example, from Martigny to Finhaut over Col de La Forclaz.

GraphHopper = 3343 m

Bikewithme = 1369 m

Google Maps = 1301 m

francois renamed this task from Replace GraphHopper elevation gain value with our more accurate value to Replace GraphHopper elevation gain with more accurate value.May 10 2018, 8:30 PM

GraphHopper API was updated, with a significant improvement, but still not as accurate as we would like. @jose Do you think we can display GraphHopper values now ?

From the previous example, elevation gain is now down to 1785 m

jose added a comment.May 20 2018, 5:02 PM

This is about 37% deviation to the value we/Google compute, so I wouldn't show it unless <10-15%. At the same time I guess for flatter rides the deviation is less.
I don't have a strong decision. I let you decide.