[Tagging] Another multipolygon question

Kevin Kenny kevin.b.kenny at gmail.com
Tue Oct 23 15:37:48 UTC 2018


On Mon, Oct 22, 2018 at 12:36 PM Adam Franco <adamfranco at gmail.com> wrote:

> Hi Dave, all,
>
> Based on this discussion I just recorded this short tutorial
> <https://youtu.be/x7SPb0JtheA> of how I use JOSM and its Relation Toolbox
> plugin to to add adjoining land-cover areas as multipolygons with shared
> boundary ways to reduce duplication and overlapping ways.
>

Thanks for recording that! Now I don't have to. :)

Your workflow is essentially the same as mine, except that I use the
regular old relation editor to add and delete ways. Works well enough for
me, and I think it's only one or two clicks more than what you're doing. I
also make a lot of use of 'replace geometry' from utlilsplugin2, since a
lot of what I'm editing was born as imports and is being replaced with
updated data from the same sources. Yes, I'm very careful not to step on
the work of local mappers when I do it.

Depending on what's going on in the field, I might have called that
hedgerow a tree_row or a hedge and used a linear feature to map it.
Similarly, at breaks in tree cover for things like power lines and
pipelines, I might use man_made=cutline. Speeds up the process a little bit
more. For what it's worth, I tend to restrict the 'cutline' tag to a
standard (in NY) four-rod right-of-way; if the cutting is larger than that,
it gets a polygon.

Hopefully this will begin to show that for complex landcover, or similarly
complex admin boundaries, that multipolygons with shared ways are actually
quicker and easier to maintain than simple areas.  I know that they're
still controversial, even among experienced mappers, but for something
complicated like West Point https://www.openstreetmap.org/relation/175474,
with a whole bunch of shared borders, rights-of-way cut out of it and what
not, I'd be really handicapped without shared ways.  I didn't get very far
on the landcover because I seldom map landcover other than in my own
neighbourhood or when fixing other people's mistakes.
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