[Tagging] Another multipolygon question

Warin 61sundowner at gmail.com
Sun Oct 21 01:40:45 UTC 2018

On 21/10/18 12:24, Kevin Kenny wrote:
>     Works great, right up until you need to maintain it.  So, you've got
>     your "natural=wood" multipolygon sharing a way with an adjoining
>     "natural=scrub".  And then, some inconsiderate developer bulldozes his
>     way across the boundary and puts up a housing development. Now what do
>     you do?  You can't unglue the boundary and shrink the two affected
>     areas to make room for the "landuse=residential" because there's only
>     one way.
>     The only option I've found is to remove the affected section of
>     boundary from one of the multipolygons, move it to the new location,
>     create a new boundary way for the other multipolygon in the proper
>     place and add it, create a new multipolygon for the development
>     and add
>     the relevant boundary ways to it, and then confirm that you haven't
>     broken any of the multipolygons involved.  It's painful enough that
>     it's usually faster and easier just to delete everything and re-create
>     them from scratch as ordinary closed ways.
> I actually do edit those things pretty routinely. It involves 
> redrawing only for the added ways.
> Draw the new closed polygon representing the landuse=residential. Make 
> it a multipolygon immediately.
> Insert nodes at the intersections of this closed way with the existing 
> ways (if you didn't draw it that way to start with). Split the old and 
> new ways on the nodes. (Splitting is safe - they're multipolygons 
> already.) JOSM has an 'add nodes at intersections' feature that helps 
> with this.
> Edit each of the old multipolygons to replace their old boundaries 
> with the new ones. That's just 'remove the old ways, insert the new 
> ones' in the relation editor.
> Finally, delete any ways that are now unused.
> I can do this *lots* faster than I can redraw an irregular boundary, 
> at least in JOSM. (I'm not skilled enough with iD to comment. it 
> wasn't much harder in Meerkartor when I tried it.)

An area of sand I introduced .. between a natural coastline, a tree area 
and a water area... Relation: 8718211. Using JOSM.
Yes the coastline was already a relation, as was the tree area.. I don't 
remember what the water areas was.. probably a relation too.

Most, if not all, the coastlines I deal with are relations.
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