[mkgmap-dev] Multipolygon relation as inner/outer of multipolygon

Tue Apr 24 18:20:33 BST 2018

Hi Ticker,

I looked at some examples and I think they are all plain mapping errors, so 
I think we should ignore them. 

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
Gesendet: Dienstag, 24. April 2018 18:58:19
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] Multipolygon relation as inner/outer of multipolygon

Hi Gerd

With "British Isles" most are in Scotland:

http://www.openstreetmap.org/relation/5396134
http://www.openstreetmap.org/relation/7528106
http://www.openstreetmap.org/relation/4537320
http://www.openstreetmap.org/relation/4537321
http://www.openstreetmap.org/relation/1959008

+ 11 others.

I also noticed that I didn't change the error to a warning in the
patch.

Reading through the wiki, you're right; inner and outer are supposed to
be ways. Only subarea is allowed to be a relation. When I was looking
at the OSM documentation beforek, for some reason I jumped to the
conclusion that inner/outer could be relations. It seems a natural
thing to allow. Maybe there was a mention of the idea in the discussion
area.

Ticker

On Tue, 2018-04-24 at 16:02 +0000, Gerd Petermann wrote:
> Hi Ticker,
>
> my understanding is that a valid multipolygon doesn't contain other
> relations. Where did you find them?
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
> Gesendet: Dienstag, 24. April 2018 17:42:57
> An: mkgmap development
> Betreff: [mkgmap-dev] Multipolygon relation as inner/outer of
> multipolygon
>
> Hi
>
> A while ago I noticed that mkgmap doesn't handle the case where the
> inner or outer of a multipolygon relation is a multipolygon.
>
> It doesn't handle it in two ways:
>
> 1/ During the reading of relations, if the relation references
> another
> relation that hasn't been read yet, it is added to a deferred list
> and
> when the second one is defined, the element is added to the first.
> However, for multiPolygons, the processing is performed as each one
> is
> read.
>
> 2/ In MultiPolygonRelation, an inner or outer that is a multipolygon
> relation is not handled; instead the warning "Non way member in role"
> is generated.
>
> The above warning is also generated for members with role "subarea";
> these should be ignored without warning.
>
> I've attached a patch to generated warnings in case 1/ and to improve
> the warnings in case 2/. In the longer term it should be implemented.
>
> I was surprised how few inner/outer as multipolygon there are in
> OSM/British Isles. Maybe it isn't well supported by the various map
> generating software packages and so people don't use it.
>
> Regards
> Ticker
>
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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