[OSM-talk] Best way to draw areas with holes?
chillly809 at yahoo.co.uk
Thu Dec 20 20:04:56 GMT 2007
Since the original question mentioned multiple holes I thought I'd try with more than one hole in the area. It didn't work. A single inner polygon in a landuse=forest rendered a hole, but two inner polygons didn't render any holes.
> Jon Burgess wrote:
> On Thu, 2007-12-20 at 19:59 +0200, Rahkonen Jukka wrote:
> > > Use the multipolygon relation.
> > > It'll be rendered by the Mapnik layer at least.
> > > http://wiki.openstreetmap.org/index.php/Relations/Multipolygon
> > > Unfortunately you can't do that in Potlatch yet, so you'll need
> > > using JOSM or some other editor which supports relations.
> > Hi,
> > I tried to read and understand relations, and concluded that
main purpose probably is to keep newbies out of here :)
> > Could some kind person explain to simple minded me what should
actually do if I have one outer ring and one or more inner rings and I
to make a polygon with correct number of holes out of them
relations? How on earth can I select the rings which belong together and
which is outer and which are inner ones? Or is there already a
somewhere in wiki?
> 1) Create the outer and inner rings each as a single way.
> 2) Make sure you have the 'Relations' information open by enabling the
> relation icon (the bottom on on the list down the left hand side).
> 3) Select them all the ways for you relation
> 4) In the relation box click 'Add'
> 5) A new window appears. Click 'Add Set' to add the selected ways into
> the relation
> 6) In top half of the window click on the blank box below key and enter
> 'type'. Under value add 'multipolygon'
> 7) Then you need to define the 'role' for each way. Click on each
> way members in turn an then use the 'Select' button in the dialogue to
> highlight this in the main map window.
> 8) Set the 'Role' value for each inner ring to 'inner', and for the
> outside ring set the role to 'outer'.
> Note that many existing multipolygon relations do not have the 'role'
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> talk at openstreetmap.org
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