Ralf, Have you tried
ST_MakePolygon(ST_LineFromMultiPoint(multipoint)) Hope that helps, Regina -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ralf Sent: Monday, July 14, 2008 12:29 PM To: [email protected] Subject: [postgis-users] Convert MULTIPOINT to POLYGON Hey! Is there a simple way to create a polygon out of a multipoint? I have a table with points (nodes) and another table ways. Every single way is defined through two or more nodes. The two tables are connected through way_nodes (it's an import from openstreetmap.org using osmosis!). I figured out how to get all ways that are closed: SELECT ways.id FROM ways WHERE ST_IsClosed( (SELECT ST_LineFromMultiPoint( Collect(n.geom) ) FROM nodes n LEFT JOIN way_nodes wn ON n.id=wn.node_id WHERE ways.id=wn.way_id) ) Now I am trying to store these closed ways as a polygon into another, new table. While doing that, I have to convert the MULTIPOINT that is returned by the Collect()-function into a POLYGON: INSERT INTO way_geometry SELECT ways.id, ( SELECT 'GeomFromText(\'' || replace( astext( Collect(nodes.geom) ), 'MULTIPOINT', 'POLYGON(') || ')\', 4326)' FROM nodes LEFT JOIN way_nodes ON nodes.id=way_nodes.node_id WHERE way_nodes.way_id=ways.id ) FROM ways WHERE ST_IsClosed( (SELECT ST_LineFromMultiPoint( Collect(n.geom) ) FROM nodes n LEFT JOIN way_nodes wn ON n.id=wn.node_id WHERE ways.id=wn.way_id) ) AND ST_NumPoints( (SELECT ST_LineFromMultiPoint( Collect(n.geom) ) FROM nodes n LEFT JOIN way_nodes wn ON n.id=wn.node_id WHERE ways.id=wn.way_id) ) >= 3 ; This always responds the error "parse error - invalid geometry". When I INSERT one of these lines by hand everything works fine. Is there another function to convert a MULTIPOINT into a POLYGON, maybe without using AsText()? Or does anyone have another idea to deal with this? Thanks a lot, Ralf _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users ----------------------------------------- The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer. _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
