> -----Original Message----- > Date: Thu, 28 Aug 2008 00:59:12 +0100 > From: "Thomas Wood" <[EMAIL PROTECTED]> > Subject: Re: [OSM-talk] Mapnik handling of highways that are also > landuse... > To: "Dermot McNally" <[EMAIL PROTECTED]> > Cc: osm <talk@openstreetmap.org> > Message-ID: > <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1 > > On Thu, Aug 28, 2008 at 12:49 AM, Dermot McNally <[EMAIL PROTECTED]> > wrote: > > Folks - with reference to this: > > > > http://www.openstreetmap.org/?lat=53.72339&lon=- > 6.34273&zoom=17&layers=B00FTF > > > > ...which is a section of the Mapnik render of the outcome of the very > > successful Drogheda Mapping Party in Ireland. Towards the centre of > > the map, you'll see what is represented as an oval area of residential > > highway. I can almost see why, but it struck me that it represents > > unwanted behaviour that could possibly be fixed. > > > > What we have here is a closed way of type highway=residential. > > Importantly, it isn't tagged as an area. It _is_ tagged (the same way) > > as landuse=grass. So without understanding the internals of Mapnik, > > it's as though the landuse, which applies at area-level, infects the > > highway tag and causes it to be considered as an area too. > > > Correct > > > > Clearly, I could simply draw a second way through the same nodes, and > > there are plenty of heated discussions over which approach is the > > saner. But it feels as though this tag combination ought to be able to > > render correctly as is. > > Mapnik still likes the one way per feature way of doing things, (as a > matter of fact, so do I, seems more logical that the two can be > separated if required later) >
Personally I prefer to recommend that you definer the area of grass using a separate way that uses the same nodes as the residential road, but which is certainly a separate way from the road. You may prefer to define it as a separate way using separate nodes as this can make editing easier in the short term, however Richard explained yesterday on talk how to use '/' to select from the different ways associated with the same node which I will investigate. Using the approach you have tried is definitely to be discouraged imho, and mixes up two different things into one way. As a longer term discussion I am interested in morphing the 'multi-polygon' relation into a 'polygon' relation so it can be used as an alternative ways of defining areas. The relation would need to allow a number of linear features to form the boundary of the area. The relation would then hold the tags that are associated with the area (in this case 'landuse=grass'). The relation could also be able to refer to zero or more 'inner' areas which can be defined in a similar way to define 'holes' in polygons. This approach allows a single 'edge' to be part of a number of areas (I gave the example of the edge of a park also being the boundary for the borough in a previous post). Currently the approach of using boundary:left=Ipswich for part of the boundary is not compatible with have a single way defining the area of the park. I am also advocating that we dump the current boundary left: and right: tagging in favour of using the 'boundary' relation for boundaries. I might come up with a technical demonstrator for this in the near future so explore how it might work in practice. There is more discussion on polygons and relations here: http://wiki.openstreetmap.org/index.php/Talk:Relation:multipolygon And the boundary relation here: http://wiki.openstreetmap.org/index.php/Relations/Proposed/Boundaries If this approach was used we would be able to run with both coding systems in the short term and possibly then deprecate ways being used for areas and boundaries in the longer term. Any other thoughts? Am I wasting my time on this idea, or do others see value in it? Is so would it be useful to produce some trial rendering or would someone like to make osmarender or Mapnik handle it? Regards, Peter(Ito) _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
