[Openstreetmap-dev] Re: [Openstreetmap] Shapefiles

strk strk at keybit.net
Thu Dec 15 13:41:13 GMT 2005


On Thu, Dec 15, 2005 at 12:41:36PM +0000, Tom Carden wrote:
> Nick Whitelegg wrote:
> > Think also that it would be a good idea at some stage to incorporate
> > polygons into the native "OSM" format. 
> 
> Sure, sounds wise.  I'd encourage the re-use of existing XML-y shape 
> descriptions and namespaces if appropriate.  (Or at least the liberal 
> 'borrowing' of conventions from other formats - e.g.SVG - to make 
> translation into those formats as simple as possible).
> 
> >These could incorporate nodes eg.
> >
> > <polygon uid=".." tags="...">
> > <node uid=".." tags=".." />
> > <node uid=".." tags=".." />
> > </polygon>
> >  
> 
> Not sure there's any need to obsessively re-use the node datatype - 
> what's the application for a polygon with separate tags for each point?  
> (Still not sure about allowing tags for nodes which are part of 
> segments, myself, but it seems that's already happened...)

You might be interested in the draft Topology implementation
in the upcoming PostGIS 1.1.0 release. The wiki contains
some information about data model, which is derived from ISO
SQL/MM documents:

http://postgis.refractions.net/support/wiki/index.php?PostgisTopology

(polygons are composed of edges, not nodes)

--strk;




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