[postgis-tickets] [PostGIS] #5105: False topology invalidity returned in presence of dangling edgerings

[PostGIS]

#5105: False topology invalidity returned in presence of dangling edgerings
-----------------------+---------------------------
  Reporter:  strk      |      Owner:  strk
      Type:  defect    |     Status:  new
  Priority:  medium    |  Milestone:  PostGIS 3.3.0
 Component:  topology  |    Version:  master
Resolution:            |   Keywords:  reliability
-----------------------+---------------------------

Comment (by strk):

 I isolated the 2 edgerings reported by ValidateTopology as being
 duplicated "shells" for face 0,
 surprisingly the ST_Area function reports a non-zero area for them:
 {{{
 =# select ring_id, ST_IsSimple(g), ST_Area(ST_MakePolygon(g)),
 ST_IsPolygonCCW(ST_MakePolygon(g)) from test_flatring;
  ring_id | st_issimple |        st_area         | st_ispolygonccw
 ---------+-------------+------------------------+-----------------
  -850133 | f           |  2.961306592939839e-21 | t
  -850131 | f           | 3.6390156688045347e-20 | f
 (2 rows)
 }}}

 This is unexpected, because the list of edges composing the ring
 (effectively ONE edge for the -850131 case) form a completely FLAT
 geometry, so should have an area of 0. Maybe I should file a separate
 ticket for this problem.

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5105#comment:8>
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