[postgis-devel] [PostGIS] #2067: Invalid polygons give empty centroids

[PostGIS]

#2067: Invalid polygons give empty centroids
---------------------+------------------------------------------------------
 Reporter:  sderle   |       Owner:  pramsey      
     Type:  defect   |      Status:  new          
 Priority:  medium   |   Milestone:  PostGIS 1.5.6
Component:  postgis  |     Version:  1.5.X        
 Keywords:           |  
---------------------+------------------------------------------------------
 {{{

 # select astext(way) from planet_osm_polygon where
 st_geometrytype(st_centroid(way)) <> 'ST_Point';

 astext
 ---------------------------------------------------
  POLYGON((-73.042747 40.961426,-73.042571 40.961971,-73.042747
  40.961426,-73.0426927 40.9610055,-73.0426645 40.960956,-73.0426927
  40.9610055,-73.042747 40.961426))
  POLYGON((-73.042747 40.961426,-73.042571 40.961971,-73.042747
  40.961426,-73.0426927 40.9610055,-73.0426645 40.960956,-73.0426927
  40.9610055,-73.042747 40.961426))
  POLYGON((-65.912493 18.220862,-65.911621 18.220036,-65.911401
  18.219793,-65.910957 18.21916,-65.910925 18.219101,-65.910668
  18.218553,-65.910398 18.217805,-65.910024 18.216882,-65.90946
  18.215632,-65.909338 18.215362,-65.908986 18.21459,-65.908951
  18.214513,-65.908844 18.214279,-65.90866 18.213946,-65.908404
  18.213684,-65.908044 18.213497,-65.907776 18.213446,-65.907033
  18.213408,-65.906508 18.213338,-65.906074 18.213238,-65.905838
  18.213183,-65.906074 18.213238,-65.906508 18.213338,-65.907033
  18.213408,-65.907776 18.213446,-65.908044 18.213497,-65.908404
  18.213684,-65.90866 18.213946,-65.908844 18.214279,-65.908951
  18.214513,-65.908986 18.21459,-65.909338 18.215362,-65.90946
  18.215632,-65.910024 18.216882,-65.910398 18.217805,-65.910668
  18.218553,-65.910925 18.219101,-65.910957 18.21916,-65.911401
  18.219793,-65.911621 18.220036,-65.912493 18.220862))
 (3 rows)

 # select st_isvalid(way) from planet_osm_polygon where
 st_geometrytype(st_centroid(way)) <> 'ST_Point';

 NOTICE:  Self-intersection at or near point -73.042747000000006
 40.961426000000003
 NOTICE:  Self-intersection at or near point -73.042747000000006
 40.961426000000003
 NOTICE:  Self-intersection at or near point -65.912492999999998 18.220862

 st_isvalid
 ------------
 f
 f
 f
 (3 rows)

 # select astext(st_centroid(way)) from planet_osm_polygon where
 st_geometrytype(st_centroid(way)) <> 'ST_Point';

           astext
 --------------------------
  GEOMETRYCOLLECTION EMPTY
  GEOMETRYCOLLECTION EMPTY
  GEOMETRYCOLLECTION EMPTY
 (3 rows)

 # select postgis_version();
             postgis_version
 ---------------------------------------
 1.5 USE_GEOS=1 USE_PROJ=1 USE_STATS=1
 (1 row)

 }}}

 There are over 2,000 other geometries in this table for which ST_IsValid()
 fails, but which still produce centroids of type ST_Point.

 System is Ubuntu 11.10 with stock GEOS 3.3.3 installed.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2067>
PostGIS <http://trac.osgeo.org/postgis/>
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