[Tagging] Peak-based mountain range proof of concept

[Florian Kratochwil]

The discussion split up into
1) mountain ranges (could possibly be tagged without areas)
2) areas (fuzzy) which can not be substituted by nodes/ways
I will continue with 1), but lets not forget about 2). Maybe we get 
insights from 1) we can use in 2).

Am 29.12.20 um 04:20 schrieb Brian M. Sperlongano:
> In light of the ongoing "how to tag a mountain range" discussion, I 
> created the following object which maps the Green Mountains in 
> Vermont, USA.  As a flatlander, I had substantial help from a local 
> Vermonter, who understood the topography and which peaks should be 
> included.  It is modeled simply as a relation of all the mountain 
> peaks in the range:
>
> https://www.openstreetmap.org/relation/12102399
>
> I offer this as a proof of concept of one possible way to map a 
> mountain range, hopefully to help further the discussion.  I am not 
> necessarily advocating for this scheme or the specific tagging that I 
> have on that object (and I'm not planning to write a proposal around 
> it), but I thought it would be useful to demonstrate a concrete 
> example that we could all look at.
>
Thank you Brian! Perfect example for this discussion.

My thoughts on this method:

  * In my head, mountain ranges are areas and not a collection of peaks.
    This follows the idea that even a mountain isn't just the peak but
    the whole (sometimes fuzzy) 3d object from the surrounding valleys
    to the top. But this doesn't say "mapping mountain ranges as
    collection of elements that are definitely inside, and then
    calculate the outline" is the best way to get to those areas. I dont
    want to rule this idea out right now.
  * To better define the "outline" of a mountain range, we could assign
    "inner/outer" roles to the elements. In your example of the Green
    Mountains, I don't know if the southern end is "one big fat" end, or
    if it has "two legs". Is Harriman Reservoir in it or not? If we
    assign the roles, you could give Haystack Mountain "outer", then I
    would say Harriman Reservoir is not inside. If Haystack Mountain
    gets nothing, or an "inner" role, we could draw an imaginary line
    from Stowe Montain to The Dome which leads to "Harriman Reservoir is
    in the Green Mountains".
  * Are there some mountain Ranges with "holes" / inner rings? I
    guess/hope no. Otherwise, we could get problems if someone adds a
    peak "in" an existing mountain_range relation but does not know
    about this relation. Because this would punch a hole. But if we say,
    mountain ranges dont have holes, it could be assumed the new peak is
    part of the range. Validators like osmose could detect those lone
    peaks somehow to double check.
  * The relation is not limited to peaks only. It could contain ridges
    and aretes, maybe valleys and mountain passes, or (if we once map
    them) massifs / mountain-polygons. But I guess we should keep it
    rather simple, so maybe lets dont do that.
  * As peaks have calculable (you need elevation data) "priorities"
    (https://en.wikipedia.org/wiki/Topographic_prominence) a renderer
    could weigh them to find the best "label curve". There is no need to
    draw an (unverifiable) label line.

Best Florian
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