[OSM-dev] Relations, landuse, and gml2osm mess

Iván Sánchez Ortega ivansanchez at escomposlinux.org
Sun Mar 30 14:15:37 BST 2008


El Domingo, 30 de Marzo de 2008, Frederik Ramm escribió:
> > If I use a relation of ways (making up a ring) as the outer (or inner)
> > hull of a multipolygon relation[2], will it work?
>
> Don't think it would currently, but it sure could be arranged. Some
> editors (*cough*) still have problems with nested relations though.[*]

My question was more related to the main renderers (mapnik and osmarender).

> While it is true that this would introduce a kind of asymmetry, I
> think it would be rather pragmatic as you'd seldom need multiple ways
> on the "inner" ring.

"Seldom" != "never", so it may be needed. Given tie, I'd show you some cases 
where it will be needed.

> About the GML:
>
> Out of interest about the whole GML stuff - if you apply the XSLT from
> here [...] to your OSM file, does the result even remotely look like the GML 
> that you originally put in?

I won't even bother running it - it is missing things like linearRings, 
polygons, multiPoligons on the GML side, and relations on the OSM side. It 
won't look anything like it, provided that I'm tagging the whole relation and 
not the outer rings.

> I have heard people say that GML supports topology,

Ha!

Given my experiences with GML, it supports topology in some alternate universe 
only.

Even the implementation of the WFS service for the road network was borked - I 
was missing endpoints of lineStrings and had to hack their coordinates by the 
bounding box, not to mention how many 

> move the forest border, and the road moves as well? Until now I thought that 
> any OSM to GML conversion would make two distinct objects, one forest, one 
> road, and they'd lose their connection.

They are in two separate layers, which are stored in two separate GML files 
(or WFS-T live connections). I don't think most GIS software would allow 
sharing topology between layers.

( See? That's one thing I really like about OSM: everything is in the same 
layer, everything is topologically connected )


-- 
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Iván Sánchez Ortega <ivansanchez at escomposlinux.org>

Palabras Textuales #307: "Este monitor no me deja imprimir!"
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