[postgis-users] reparing invalid geometry (polygon defined by oneor two points)

[Obe, Regina]

Ivan,

I think a variant of Simon's script would work for you except instead of
keeping rings with a large enough hole, keep rings that are closed and
have enough points

http://www.spatialdbadvisor.com/postgis_tips_tricks/92/filtering-rings-i
n-polygon-postgis

so something like

CREATE OR REPLACE FUNCTION remove_invalidrings(geometry)
  RETURNS geometry AS
$BODY$
SELECT ST_BuildArea(ST_Collect(b.final_geom)) as filtered_geom
  FROM (SELECT ST_MakePolygon((/* Get outer ring of polygon */
		SELECT ST_ExteriorRing(a.the_geom) as outer_ring /* ie
the outer ring */
		),  ARRAY(/* Get all inner rings > a particular area */
		 SELECT ST_ExteriorRing(b.geom) as inner_ring
		   FROM (SELECT (ST_DumpRings(a.the_geom)).*) b
		  WHERE b.path[1] > 0 /* ie not the outer ring */
		    AND (ST_NPoints(b.geom) > 2 AND ST_IsClosed(b.geom))
		) ) as final_geom
         FROM (SELECT ST_GeometryN(ST_Multi($1),/*ST_Multi converts any
Single Polygons to MultiPolygons */
 
generate_series(1,ST_NumGeometries(ST_Multi($1)))
                                   ) as the_geom
               ) a
       ) b
$BODY$
  LANGUAGE 'sql' IMMUTABLE;

Hope that helps,
Regina

 

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Ivan
Mincik
Sent: Tuesday, March 24, 2009 5:03 AM
To: PostGIS Users Discussion
Subject: [postgis-users] reparing invalid geometry (polygon defined by
oneor two points)

Dear PostGIS users,
we have quite huge MULTIPOLYGON database table containing some 3
percents of invalid geometries. 
Most problematic to repair are MULTIPOLYGONs which often contain polygon
defined by one or two points.

Example is here (second polygon is defined by one point):
MULTIPOLYGON(((-266469.87 -1233431.41,-266423.25 -1233425.84,-266423.23
-1233426.17,-266422.74 -1233434.54,-266422.75 -1233439.44,-266425.68
-1233439.9,
-266457.02 -1233444.89,-266463.17 -1233437.07,-266463.27
-1233436.29,-266469.15 -1233437.08,-266469.84 -1233431.65,-266469.87
-1233431.41),(-266463.92 -1233431.02),
(-266459.41 -1233430.46,-266458.67 -1233436.67,-266451.29
-1233435.76,-266451.1 -1233437.26,-266438.9 -1233435.75,-266439.07
-1233434.35,-266426.37 -1233432.65,-266427.07 -1233426.46,
-266439.85 -1233428.04,-266459.41 -1233430.46)))

It is not possible to run buffer(0) or many other functions on these
geometries because of "POSTGIS2GEOS conversion failed" (no suprise in
case of such non-sense geometry).

Is there any possibility how to repair them directly in database?


Thanks
Ivan

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