[postgis-devel] [PostGIS] #1641: SQL/MM Spatial exception - geometry crosses an edge

[PostGIS]

#1641: SQL/MM Spatial exception - geometry crosses an edge
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 Reporter:  lrssvt    |       Owner:  strk         
     Type:  defect    |      Status:  new          
 Priority:  medium    |   Milestone:  PostGIS 2.0.0
Component:  topology  |     Version:  2.0.x        
 Keywords:            |  
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Comment(by strk):

 Alright in this case noding of the two lines results in the line being
 added (the semi-vertical one) being split in two. Then first point is
 added as a node (the lowest) and when last point is added as a note the
 code fails to find this second node _on_the_ existing line.

 The query is in the form: ST_Dwithin(intersection_node, existing_line, 0)

 Well, it fails. Using a tolerance of 1e-17 still fails. 1e-16 succeeds in
 finding it.
 This part of the code isn't attempting to do any tolerance. We could add
 that.

 But still, what GEOS does is completely out of our control as GEOS uses
 its own heuristic to get to a result, responding to topology exceptions by
 reducing precision (for example). So it could still be possible for us to
 use a too low tolerance to account for what GEOS did.

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/1641#comment:5>
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