[OSM-talk-ie] L-roads terrible signing or the lack thereof.

[Dermot McNally]

2008/11/17 robin grindrod <robingrindrod at gmail.com>:

> Thanks very much for your help. Sorry if this is a stupid question but
> this is the first time I have used relations, what exactly do you mean
> by inner and outer roles?
> Thanks again,

Ah - well, we know there are no stupid questions. I'll start by
quoting the bible on multipolygon relations:

http://wiki.openstreetmap.org/wiki/Relation:multipolygon

Every member of a relation _may_ have a role attached, which JOSM
displays to the left of the member itself in the lower part of the
relation editor. A multipolygon must consist of exactly one member
having role "outer" (in this case, the riverbank area) and as many as
you like having role "inner" (the holes, or islands in this case).

So in a relation with two members and no roles defined, the renderer
doesn't know which one is the shape and which ones are holes (OK, it
could be calculated, but you get the idea).

Make sense?
Dermot

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