Added quest for mtb:scale

[torhovland]

Fixes #1850.

The icon can be improved. Also, the photos for value 2-5 are low resolution and had to be upscaled. Better photos would be good.

[matkoniecz]

Looks nice! Though I would be unable to distinguish "some trial techniques" and "very few can ride here"

[torhovland]

Yeah, this is based on the Wiki categorisation, but obviously shortened to fit. I am happy to adjust the text and photos if somebody has any suggestions.

Having said that, I think it is fine as it is. There are quite a few riders who have "some trials technique", i.e. enough to lift the rear wheel through a tight turn, while the next category indicates that even this is not enough.

[westnordost]

Heya, I wrote a longer comment in the ticket. In a nutshell, I think it should be implemented as an overlay, instead.

From a cursory look, from the technical perspective it looks very fine. A few comments, though:

• The pictures for scale 2-5 are super-blurry, I'd like to very much encourage you to find pictures with at least a resolution of 384x384 pixels. So, these miniature-pictures are from the wiki(?) - maybe update the wiki with proper pictures then, too? It can only help to improve the overall quality of the data collected - with or without StreetComplete.
  Current pictures: As a layman, the jump between scale 1 and scale 2 seems really large to me (the loose rock on scale 2 picture looks dangerous,.... if he would go in the gravel in-between, I'd understand). Also, I do not see a difference between scale 3 and 4. The jump between scale 5 and 6 is probably deliberate though(?)

• translations are done exclusively in POEditor, strings in values-XX will be overwritten by an import from POEditor

• I am not content with the descriptions. "advanced riding skills", "very good skills",... etc. are absolutely subjective. The descriptions should not describe how advanced you gotta be (on a scala from 0-6) but should try its best to nail down some things the user can see, with his eyes. There must be some objective properties described in the wiki that would help to classify the mtb scale! See also Ask for MTB difficulty for paths #1850 (comment) .

• Note that if the descriptions turns out to be longer, and it is already quite long, I suggest to use the list style as used by the smoothness quest, where the pictures are on the left and the description is on the right

• The icon is much too detailed! You know how small of an icon it is displayed as. Lines should not be thinner than 4px (when assuming a size of 128x128px). Suggestion: Use the bicycle icon bicycle.svg and the bump from car_bumpy.svg, rotate the bicycle a bit and/or make the bump look more like a rock, done. Also, I think a green background is better here - it is about bicycles, yes, but it is about mountainbiking which is a sport, so the "leisure/amenity" color seems to be more fitting here. Alternatively, leave the icon to me and just use bicycle.svg as a placeholder.

[mnalis]

Overlay might indeed be only workable solution. E.g. this overpass query shows what current query does in the middle of the urban environment (where there ideally should be close to zero quests about mtb:scale=*, ignoring occasional hilly parks):

type:way
and highway ~ "path|track"
and ("mtb:scale" is null)
and (surface ~ "ground|earth|dirt|soil|grass|sand|mud|ice|salt|snow" or smoothness ~ "bad|very_bad|horrible|very_horrible" )
and (access !~ "private|no" or (foot=* and foot !~ "private|no") or (bicycle=* and bicycle !~ "private|no"))
and (sidewalk !~ "both|left|right")

Upon taking a closer look at random ways selected, I do not think that refining the query for Quest might improve situation significantly. Requiring the incline=* would help with reducing the spurious quests in citires, but then it would miss flat parts of MTB paths in woods too, and many inclined ways do not have incline=* tagged anyway.
And I do not think that StreetComplete can recognize and automatically deselect urban areas currently (e.g. landuse=residental etc)?

Thus, converting this to Overlay seems to me like best solution (and similar query could be used for coloring it)

[westnordost]

No feedback since 5+ months, closing.

This would need to be re-implemented as an overlay anyway, there is little which could be borrowed from the current state of this PR. So, for an overlay, a new PR should be created.