Am 23.09.2013 11:59, schrieb Paul Norman: >> From: Martin Koppenhoefer [mailto:dieterdre...@gmail.com] >> Subject: Re: [OSM-talk] osm2pgsql multipolygon parsing >> >> it has a different meaning. tags on a closed way are for the whole area >> inside the way, tags on a mp relation are for the area of the outer >> minus the inner ways. > > Unless the closed way is a member of a multipolygon relation with no other > tags on the relation - then you'll have a resulting area with a hole. This > is a very well established means of tagging areas with holes (~22% of > type=multipolygon relations have no other tags). It's well established, but it's less correct from a theoretical point of view, and establishment is produced here by software that supports wrong tagging - in the past. You propose to leave it as it is, which means software should estimate the meaning because often there are errors in the tagging, while I proposed (and as far as I understand at least Martin supports that) not to ignore these errors with the goal to teach mappers about what's correct instead of teaching them what's correct enough for application X (be it the default mapnik style and -pipeline).
> The issues raised originally in the ticket are best explored through > examples > > The first case is a way with natural=water and a MP relation with no other > tags. Both old osm2pgsql (0.82) and latest master version from git create an > area with a hole with natural=water on the area. There are no suggestions of > changing this. Problem: Let's say the multipolygon relation was tagged before as depth=shallow (and someone wanted to mark parts of the water as not deep - e.g. not deep enough for boats). Let's say another mapper came along and found this strange tags and - removing them - accidently left a multipolygon without tags. This changes the meaning of stuff never touched again, as you would now count the natural=water only for the area covered by the multipolygon, excluding the hole. > The second is a way with natural=water and a MP relation with name=foo (with > the way as a member). Old osm2pgsql created an area with a hole with > natural=water, name=foo, latest master does too. What if the inner part does NOT have that name, but only the outer ring? What if that is what somebody wanted to say? regards Peter _______________________________________________ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
