[OSM-talk] New tool in Potlatch 2 for areas that share a way

[Daniel Sabo]

On Jan 30, 2011, at 5:27 PM, Steve Bennett wrote:

> On Mon, Jan 31, 2011 at 11:39 AM, Daniel Sabo <danielsabo at gmail.com> wrote:
>> This is a really bad idea. Drawing collinear features by sharing nodes is NEVER a good idea beyond 1 or 2 shared corners, that's what multipolygons are for.
> 
> Does that apply for coastlines as well? Or do coastlines not even need
> the multipolygon?

I'm honestly not sure about coastlines, because I'm not sure how osm2pgsql's coastline removal works, but inland lakes (natural=water) definitely work with multipolygons.

>> When the ways get attached to large objects (like an administrative boundary or national park) it becomes impossible to edit them from an extract without unintended side effects.
> 
> Good to know. I wonder how we can make multipolygons more user
> friendly? Maybe a magic "convert to multipolygon" tool, that starts
> with one way (say the golf course in the previous example), converts
> it to a multipolygon, and converts any other affected ways (the
> landuse=industrial) as well.
> 
> Steve

I've been thinking about this too, because multipolygons still a lot are harder in Potlatch than JOSM. I would think we could make a tool smart enough to handle it but I don't have any experience with ActionScript programming.

e.g.
Select two collinear polygons , click "convert to multipolygon", tool make a new way for each collinear segment, then make a new multipolygon for each with all the new segments as role=outer.

Right now Potlatch doesn't even render landuse multipolygons though, so there's not much incentive for people to click a button like that :).

I do appreciate that my pro-multipolygon perspective comes from working primarily with JOSM where they've gotten very easy to use, Potlatch users probably are as annoyed by working with my multipolygons as much as I am by their collinear ways.

- Daniel