[geos-devel] [GEOS] #588: valid polygon when cw, not valid when ccw

GEOS geos-trac at osgeo.org
Wed Sep 12 03:14:56 PDT 2012


#588: valid polygon when cw, not valid when ccw
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 Reporter:  olivier80   |       Owner:  geos-devel@…              
     Type:  defect      |      Status:  new                       
 Priority:  major       |   Milestone:  3.3.6                     
Component:  Default     |     Version:  3.3.5                     
 Severity:  Unassigned  |    Keywords:                            
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Comment(by strk):

 The polygon ring has 7 points, but it's a 4 sides polygon. So 2 vertices
 are very close to other vertices.

 I'd love to have a function (in postgis) to analyze these cases and answer
 questions like: what's the minimum distance between two consecutive
 vertices ? what's the minimum distance between any two vertices ?

 Simplifying the geometry with a tolerance of 1e-10 is enough to fix the
 invalidity, but anyway the robustness problem exists. I didn't try with
 JTS but I suspect it may be an issue there as well.

-- 
Ticket URL: <http://trac.osgeo.org/geos/ticket/588#comment:3>
GEOS <http://geos.refractions.net/>
GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology Suite (JTS).


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