On 29/07/18 20:37, Paul Allen wrote:
On Sun, Jul 29, 2018 at 12:57 AM, Graeme Fitzpatrick
<graemefi...@gmail.com <mailto:graemefi...@gmail.com>> wrote:
The problem with that of course, as Warin mentioned, is what would
it hypothetically render as - grass / sand / rock / scrub etc etc?
If you simply define an area that is absent of woodland with no tags
defining what it is, then it renders as an absence of
woodland. It is a hole in the woodland that renders the same as
whatever is outside the woodland, i.e., bare map. It's
only if you add tags to the inner area that define it as
grass/sand/whatever that it renders as anything other than "bare
map." Or if there's a larger area enclosing the wood (such as a
nature reserve) then the hole will (I haven't tested that,
so make it "should" rather than "will") still render the same as
outside the wood.
I've poked holes in a wood to handle clearings, and poked holes in
woods for ponds and quarries. It all works fine. If
you don't trust me then give it a quick try. It's a matter of minutes
to add a relation to the wood, transfer the tags from
the wood to relation, then add one of the clearings to the relation
and see what happens. If you hate the result then
it's only a few more minutes to manually revert.
I too have created relations for tree areas and made 'holes' in them for
various things. Some of those 'holes' may well be 'bare map'.
The level of detail gained is proportional to the time taken, the
resolution of the imagery and lack of cloud cover in the imagery.
Fortunately there is now more than one good image source so clouds are
less of a problem.
The problem with the present data in this area is that;
a) it does not render so 'we' don't know it is there by looking at the
rendered map.
b) it was done remotely using imagery .. so even the mapper did not know
what really was there, other than a lack of trees at that time.
c) HOT mapping may be speed driven, to get usefull data quickly to
places in need, rather than good mapping.
The problem is the presence of the tag 'landuse=clearing'
that apparently, from both imagery and language, simply mean a lack of
trees compared to the surrounding area.
It is quicker to map these 'holes' as they are much less in length
compared to the outer way.
The 'landuse=clearing' says nothing about what is inside the area ,
other than the lack of trees, it could be dirt or grass or any other
thing or things.
To my mind that tagging can be replaced with these 'holes' in a tree
relation as detailed above.
OSM looses nothing by removing the tag provided the way is incorporated
as an inner in a tree relation.
If a mapper wants to look at an individual way .. then the history of
that way is available, so they can see it came from landuse=clearing and
who the original mapper was.
I could add a tag - say a "comment=from HOT contribution, tagged
landuse=clearing" .. that should suffice.
In OSM 'we' try to tag what is on the ground, "landuse=clearing" to me
means a lack of something - not what is there, but what is not there.
And that is not something I'd even think about trying to render.
------------
Some time ago I tried to improve the mapping of the Kokoda Trail. That
included the tree relation 7575948
https://www.openstreetmap.org/relation/7575948
That does show the 'holes' where what is there has not been mapped
because it cannot be readily identified for aerial imagery.
Note: The Kokoda Trail is mapped as a 'road'. No motor vehicle has ever
been over it, other than in an aircraft.
Even a bicycle would not be a good form of transport of it. In WW2 the
Japanese did not take bicycles on it, one officer took a horse.. they
killed it.
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