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

[Rihards]

On 2017.08.13. 23:11, David Kewley wrote:
> 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?

looks very reasonable. you have added the split-off piece as a separate
way, not multipolygon, which makes it easier to handle.

nitpicking - i would disconnect it from the road here :)
http://osm.org/go/TPVmeC512?m=

> 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.-- 
 Rihards