[postgis-devel] [PostGIS] #1714: totopogeom - can't add multipolygo

PostGIS trac at osgeo.org
Wed Apr 11 02:53:52 PDT 2012

#1714: totopogeom - can't add multipolygo
 Reporter:  robe      |       Owner:  strk         
     Type:  defect    |      Status:  new          
 Priority:  medium    |   Milestone:  PostGIS 2.0.1
Component:  topology  |     Version:  trunk        
 Keywords:            |  

Comment(by strk):

 See the bogus snapping here. The green line with an arrow is one of the
 linestrings being inserted (an edge). The triangle on the top-right is the
 other line which we try to add (vertices shown in red). The triangle on
 the left is the result of snapping the top-right line to the bottom line.

 It looks like the bottom-right vertex of the line was snapped to the top-
 left vertex of the existing edge. It is surprising because the distance
 between those two vertices is ~ 0.3 (higher than the tolerance).


 To isolate the case, these are the ST_Snap inputs:
 A: LINESTRING(765795.1 2949559.2,765795.2 2949559.2,765794.9
 2949559.5,765795.1 2949559.2)
 B: LINESTRING(765795.1 2949559.2,765794.9 2949559.2,765795.2
 2949558.8,765795.1 2949559.2)
 tolerance: 0.25

 I've filed #1767 for that one.

 Here we might still want to succeed after that snapping. Note that at this
 point the snapped line is still simple, so let's see what happens

Ticket URL: <http://trac.osgeo.org/postgis/ticket/1714#comment:5>
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