[Tagging] landuse=clearing

Warin 61sundowner at gmail.com
Sun Jul 29 12:57:33 UTC 2018


On 29/07/18 20:37, Paul Allen wrote:
> On Sun, Jul 29, 2018 at 12:57 AM, Graeme Fitzpatrick 
> <graemefitz1 at gmail.com <mailto:graemefitz1 at 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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