[Talk-us] tagging a national forest boundary

Greg Troxel gdt at ir.bbn.com
Fri Oct 1 02:52:16 BST 2010


Nathan Edgars II <neroute2 at gmail.com> writes:

> On Thu, Sep 30, 2010 at 2:47 PM, Ian Dees <ian.dees at gmail.com> wrote:
>> On Thu, Sep 30, 2010 at 1:41 PM, Nathan Edgars II <neroute2 at gmail.com>
>> wrote:
>>>
>>> I'm importing the USFS data for the Ocala National Forest boundary.
>>> There's the actual forest boundary, and there are private inholdings
>>> inside the boundary that are not owned by the USFS. For flexibility,
>>> I'm making a multipolygon for each. But which one is the "real"
>>> boundary? What tags go on each?
>>
>> You're creating separate multipolygons for each of the private inholdings?
>> You should be creating one multipolygon with several internal ring ways as
>> "inner" members of the multipolygon relation. The whole multipolygon
>> relation should have whatever tags you've decided on and the member ways
>> should not have any tags.
>
> That's what I'm doing. But I then have two multipolygons: one for the
> "forest boundary" and one for this boundary minus the inholdings. The
> difference is nontrivial, since some of the inholdings go right up to
> the "forest boundary", implying that the forest actually in some way
> includes these inholdings.

I think you two might be talking past each other.

I am slightly fuzzy on multipolygons, but I think the notion is that a
multipolygon has a number of outer rings, and a number of inner rings,
and it defines the area that consists of points within an outer ring and
not within an inner ring.

So in the national forest/inholdings case, I think you have a polygon
(closed way) that is the boundary (typically drawn strongly on a
traditional topo), labeled as the forest boundary.  Then you have a
polygon for each inholding, with no particular tags required.  And then
a multipolygon with the forest boundary as outer and all the inholdings
as inner.

Sort of related, landuse= tags and landcover tags (which we don't seem
to have) should be separate.  I haven't had time to dig into this, but I
think it would be really useful if someone figured out what the
taxonomies were in the various professional disciplines that deal with
these issues, and just adopted one of them.  OSM seems to insist on
reinventing everything, and for replacing proprietary software and
proprietary data that's great, but when entire research fields have
argued about the right way to divide up land cover, it seems a shame to
start over.
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