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

Tue Apr 24 16:42:57 BST 2018

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

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