[postgis-tickets] [PostGIS] #4755: ST_Transform of valid polygon can produce invalid polygon

[PostGIS]

#4755: ST_Transform of valid polygon can produce invalid polygon
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  Reporter:  rouen    |      Owner:  pramsey
      Type:  defect   |     Status:  new
  Priority:  medium   |  Milestone:  PostGIS 3.1.0
 Component:  postgis  |    Version:  3.0.x
Resolution:           |   Keywords:  ST_Transform
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Comment (by mdavis):

 This is because there is a very narrow "gore" in the polygon, and due to
 rounding effects the transformation perturbs the coordinates forming the
 gore just enough to introduce a self-intersection.

 One way to remove the self-intersection is to round the geometry to a
 lower precision. `ST_SnapToGrid(transform_geom, 0.0000001)` makes the
 geometry valid in this case.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4755#comment:1>
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