[postgis-devel] [PostGIS] #845: ST_Intersects() precision error - returns false instead of true

[PostGIS]

#845: ST_Intersects() precision error - returns false instead of true
------------------------+---------------------------------------------------
 Reporter:  cdestigter  |       Owner:  pramsey      
     Type:  defect      |      Status:  new          
 Priority:  medium      |   Milestone:  PostGIS 2.0.0
Component:  postgis     |     Version:  1.5.X        
 Keywords:              |  
------------------------+---------------------------------------------------
 This query returns false, but the box and point intersect:
 {{{
 select st_intersects('POINT(169.69960846592 -46.5061209281002)'::geometry,
 'POLYGON((169.699607857174 -46.5061218662,169.699607857174
 -46.5061195965597,169.699608806526 -46.5061195965597,169.699608806526
 -46.5061218662,169.699607857174 -46.5061218662))'::geometry);
  st_intersects
 ---------------
  f
 (1 row)
 }}}

 More info:

 {{{
 st_relate | st_intersects | st_disjoint
 -----------+---------------+-------------
  0FFFFF212 | f             | f

 ST_Relate is correct, ST_Disjoint is correct, ST_Intersects is _wrong_

   I B E
   -----
  I 0 F F
  B F F F
  E 2 1 2
 }}}

 Tested on postgis 1.5.2. postgis_version(): 1.5 USE_GEOS=1 USE_PROJ=1
 USE_STATS=1

 Using geos via python it works:

 {{{
 >>> from django.contrib.gis import geos
 >>> p = geos.GEOSGeometry('POLYGON((169.699607857174
 -46.5061218662,169.699607857174 -46.5061195965597,169.699608806526
 -46.5061195965597,169.699608806526 -46.5061218662,169.699607857174
 -46.5061218662))')
 >>> pt = geos.GEOSGeometry('POINT(169.69960846592 -46.5061209281002)')
 >>> pt.intersects(p)
 True
 }}}

 Probably a precision error, since this polygon is very small.

 [http://postgis.refractions.net/pipermail/postgis-
 users/2011-February/028965.html postgis-users thread]

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/845>
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