[postgis-tickets] [PostGIS] #4598: spurious results of ST_Centroid on invalid polygons of type geography

[PostGIS]

#4598: spurious results of ST_Centroid on invalid polygons of type geography
----------------------+---------------------------
  Reporter:  fadi     |      Owner:  pramsey
      Type:  defect   |     Status:  closed
  Priority:  medium   |  Milestone:  PostGIS 2.5.5
 Component:  postgis  |    Version:  3.0.x
Resolution:  wontfix  |   Keywords:
----------------------+---------------------------
Changes (by robe):

 * status:  new => closed
 * resolution:   => wontfix


Comment:

 I'm going to dismiss this as a won't fix. The first one looks right


 {{{
 WITH geogs (geog) AS (VALUES
     ('POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))'::geography),
     ('POLYGON((0 0, 1 1, 1 1, 0 0))'::geography),
     ('POLYGON((0 0, 1 1, 1 0, 0 1, 0 0))'))
 SELECT
     pg_typeof(geog),
     ST_IsValidReason(geog::geometry),
     ST_AsText(ST_Centroid(geog)),
     ST_AsText(ST_Centroid(geog::geometry)),
 ST_AsText(ST_Transform(ST_Centroid(ST_Transform(geog::Geometry,_ST_BestSRID(Geog))),4326)
 )
 FROM geogs;
 }}}

 I get this:


 {{{
 POINT(0.499934819426203 0.500006912686044)
 }}}

 which isn't too far off from the geography answer.  As to handling invalid
 polygons I'm not convinced it's worth thinking about.

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4598#comment:4>
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