Hello,
I'm doing further mapping of Swedish national parks, now in the
mountains, and I have noted that natural=fell (habitat over tree line)
is not rendered.
Looking into why it seems that OSM-Carto implementors want more specific
landcover tags to be used. I don't think that (somewhat randomly)
requiring detailed landcover is a good design choice. I think it would
be better to have a defined hierarchy from more generic to more specific
tags so the map can evolve. Taking the leap to high detail mapping
directly makes covering the map very slow and sometimes inaccurate. Fell
in particular is in parts so heavily speckled with slightly different
covers it's hard to even see on the satellite photo what it is. You can
have say 30% bare rock, 20% scree and 40% heath and 10% wetland in an
area. So I guess I make that heath then as it's dominant? That would
however be more misleading than actually setting a more generic tag like
natural=fell. Forcing detailed mapping where this is very difficult to
do is not a good idea.
When we get to even higher altitude the growth disappear and we have
just bare rock and scree so it becomes easier. It can at times be quite
hard to differ between bare rock or scree though (the resolution of the
satellite photos in the mountains is often not that great).
We already have more-generic-to-more-specific landcovers in other areas,
you can provide wood without specifying tree type for example, or
wetland without specifying type of wetland. (Parenthesis: going from
more generic to more specific by adding additional specifying tags is an
elegant design, I think it's a bit unfortunate that that design is mixed
with a flat tag structure as well, but that's the way it is...).
It seems like a very odd design choice to require more detailed mapping
in alpine areas where this is rather difficult. If we look into how
official maps do it in Sweden and Norway they don't have specific
landcovers above the tree line, they have just "fell", and in addition
significant wetlands, plus waters and streams of course.
Fell indicates where we have bare mountain (above treeline), which is
the key information outdoor goers need, plus waters and significant
wetlands. Anyone that has been to these mountains know that once above
the tree line the land cover is quite predictable, it's decided by
altitude and steepness. At the fell altitude contour lines is key
information, not if it's a patch of heath or bare rock, which rather
just makes a map harder to read without providing valuable information.
So far I have tagged these areas with natural=fell. I'm thinking about
adding bare_rock at high altitude (and scree only when clear and
significant), but in the medium altitude where there is growth more
detailed mapping becomes very difficult. Heath would be the most natural
generic tag for that area, but then we loose the distinction that it's
above the tree line, as there already is some heath areas below the tree
line. Maybe adding an extra tag like "alpine=yes"? I suppose it won't
render differently from normal heath on any renderer though so we still
lose the rather significant tree line information in actual maps.
Suggestions are welcome.
/Anders
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