[Tagging] tagging the multipolygon model (was landuse and military)

Ben Laenen benlaenen at gmail.com
Sat Oct 17 12:07:21 BST 2009

Anthony wrote:
> On Fri, Oct 16, 2009 at 10:34 AM, Ben Laenen <benlaenen at gmail.com> wrote:
> > This is ground cover for example:
> > http://www.ngi.be/Templates/zoom.htm?doctitle=uittreksel&image=../images/
> >1/1/extr10_vismijn.jpg&x=452&y=452
> > http://www.ngi.be/Templates/zoom.htm?doctitle=uittreksel&image=../images/
> >1/1/extr10_duinen.jpg&x=452&y=452
> >
> > There are extra captions like "Camping", "Golf course", "Park" etc for
> > some land uses.
> I don't see the key,

See here http://www.ngi.be/Common/leg10/10000NL.htm#top (click "Bodemgebruik", 
descriptions also in English). Buildings are under "Gebouwen".

> but this looks to me like an excellent mixture of
> ground cover and land use.  In addition to the captions, you'll notice
> the buildings are different colors - I am guessing the colors
> represent the usage.

Sure, I didn't say it was exclusively ground cover (although one could argue 
that those are different kinds of buildings and thus have different ground 
cover, a bit like leafy forest vs conifers). Tagging land use btw would mean 
that the ground surrounding those buildings for things like parking lots, 
driveways... for that building would have the same land use as the building.

Anyway, that's not the point here. It's up to renderers to think what mixture 
they want to show between land use and ground cover. For example: do I show 
the entire campus as a hospital (land use) -- that's how we use the 
amenity=hospital polygon right now -- or do we just show the buildings as a 
hospital (ground cover)? Another example: landuse=greenhouse_horticulture maps 
entire area including water reservoirs and surrounding buildings (land use), 
but we need a way to map greenhouses separately as well, and the reservoirs, 
and the other buildings etc. (ground cover).

The problem is that in OSM we now have a lot of tags that are ambiguous 
between land use and ground cover, or mappers using land use tags for ground 
cover or vice versa. You can't make proper maps if you don't know what a tag 
means exactly.

> > No, we're using all those tags for two things, both land use and ground
> > cover. And often it's not clear which one.
> Good point.  Can you give us a URL of that talk page where you discussed
>  this?


> I see the problem.  I have no idea how to solve it within OSM...

I also don't have easy solutions. We need someone who's more knowledgeable on 
this subject to help us sort this out.


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