[postgis-users] Self-intersecting polygon gives ST_IsSimple=true

[Jukka Rahkonen]

Hi,

I do not understand this:

select ST_IsValid(
ST_GeomFromText(
'POLYGON (( 320 620, 460 620, 460 500, 320 620, 320 500, 180 500, 180 
620, 320 620 ))'
     ));
Result: "f".


select ST_IsValidReason(
  ST_GeomFromText(
  'POLYGON (( 320 620, 460 620, 460 500, 320 620, 320 500, 180 500, 180 
620, 320 620 ))'
      ));
Result: "Ring Self-intersection[320 620]"

select ST_IsSimple(
  ST_GeomFromText(
  'POLYGON (( 320 620, 460 620, 460 500, 320 620, 320 500, 180 500, 180 
620, 320 620 ))'
      ));
Result: "t"


Shouldn't ST_IsSimple return "false"? OpenJUMP reports that this polygon 
is "Not Simple Geometry"
I tried PostGIS versions 2.1 and 2.3, both versions give "true".

-Jukka Rahkonen-