[OSM-dev] Playing with MapServer WMS and WFS

[Peter Körner]

Am 11.09.2010 08:26, schrieb Jukka Rahkonen:
> Pretty easy and in theory it works immediately after osm2pgsql import
> without any other preprocessing. However, I did not put it into mapfile
> because rendering fails after ST_PointOnSurface failing first with some
> polygons:
> NOTICE:  TopologyException: found non-noded intersection between
> LINESTRING (8569.5 4234.62, 8623.96 4373.11) and LINESTRING (8637.48
> 4400.77, 8610.45 4345.45)at 8623.96 4373.1

Yes, that's a known problem (or feature?). OSM allows invalid geometries 
for polygons and mapnik can render them, but some postgis functions will 
fail. It is possible to use ST_IsValid but this adds a medium runtime 
penalty.

To come around this we could add an isvalid coumn to the polygon table. 
This column can be filled via a trigger or via osm2pgsql. This would 
move the penalty to the import.

Peter