On 13 September 2010 15:53, Peter Körner <[email protected]> wrote:
> 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. > There are two ways of dealing with invalid geometries. I have used in the past either ConvexHull or buffer to make them valid for analysis purpose. That's what I did for the Corine Import for France. Emilie Laffray
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