[Talk-us] natural=* and landuse=* multipolygons at the urban interface

David Kewley david.t.kewley at gmail.com
Sun Aug 13 20:11:38 UTC 2017


Development in Orange County, California pushes into areas currently
covered by polygons (often large multipolygons) tagged as natural=scrub,
landuse=meadow, or landuse=[farm|farmland]. These were part of the FMMP
import http://wiki.openstreetmap.org/wiki/California_Farms.

Mostly I try to leave those large multipologons alone, because I don't feel
confident I can handle them properly, and because I'm using iD (due to
using a Chromebook), where relation handling is rudimentary.

But I'd like to update the urban-wildland boundary, where new suburban
developments are pushing into former wildland, farmland, or (historical?)
"grazing land". See for example the new development (with 2017 imagery
recently added to Bing) at
http://www.openstreetmap.org/edit?editor=id#map=16/33.5352/-117.6034.

Editing these huge multipolygons, and reviewing others' edits to them,
becomes very cumbersome, at least to me. It seems to me probably sensible
and reasonable at the urban edge to split off small parts of these
multipolygons, e.g. at roads, to make the smaller bits easier to edit and
review in the context of the expanding urban edge.


As one test / demonstration edit (
http://www.openstreetmap.org/changeset/51090963), I carved off a bit of
natural=scrub from a large outer role of a multipolygon, into its own
polygon. I manually added new boundary way segments, stitched them together
into the existing ways, copied tags, and made the split-off piece its own
polygon, independent of its original parent multipolygon. I did the split
at an existing highway=residential object (Golden Ridge Lane).

I know, I should find a way to use JOSM, which I expect makes this much
easier. :)

Meanwhile, does this seem a reasonable approach to making the urban
interface a bit more manageable in the future? I.e. splitting off parts of
large multipolygons (so long as they don't have names or other unique
identifiers that matter, just generic tags things like natural=scrub), to
make future editing easier?

I know for the above example of a new residential area, I could make a
landuse=residential island, and make it an inner role in the surrounding
landuse=meadow multipolygon. But at some point as the urban sprawl expands,
it seems to me it makes more sense to stop pretending the area is dominated
by the natural features, and make it clear it's dominated by e.g.
landuse=residential, with possibly interspersed natural features like scrub.


What would the group suggest?

Is my test edit reasonable, or should it be reverted?

Thanks,
David


P.S. As an aside (not my main point today), the FMMP-based distinction in
this area between scrub and meadow seems awfully arbitrary. I could be
mistaken, but I don't believe the "meadow" is actually used today for
grazing nor feed harvesting, and in the aerial photography, it appears
indistinguishable from the adjacent "scrub". It appears (and I'm nearly
certain from driving by) that there's both substantial grass and
substantial woody plant cover, in similar ratios in both "meadow" and
"scrub".

I don't believe there's any current agricultural use of that land, at least
not near where I'm giving examples today. There might be some
large-acreage, semi-wildland grazing or feed harvesting activity remaining
in Orange County, but I've not noticed any.

As documented in the FMMP wiki page
http://wiki.openstreetmap.org/wiki/California_Farms, the FMMP designation
"Grazing Land" was mapped to landuse=meadow.

But the FMMP designation of "Grazing Land" explicitly does not mean that
there *is* grazing activity there, just that it is "...land on which the
existing vegetation, whether grown naturally or through management, is
suitable for grazing or browsing of livestock." (See for example
http://www.conservation.ca.gov/dlrp/fmmp/Documents/soil_criteria.pdf.) So
wildlands that will never again see livestock, or harvesting for livestock
feed, can still be designated Grazing Land by FMMP. Those areas map better
to natural=grassland or natural=scrub, I think.

So landuse=meadow seems less useful than natural=scrub or natural=grassland
for many of these areas. Even though this is a secondary point today, I'd
welcome comments on this as well.
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