[postgis-devel] [PostGIS] #845: ST_Intersects() precision error - returns false instead of true

[PostGIS]

#845: ST_Intersects() precision error - returns false instead of true
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 Reporter:  cdestigter  |       Owner:  pramsey      
     Type:  defect      |      Status:  new          
 Priority:  medium      |   Milestone:  PostGIS 2.0.0
Component:  postgis     |     Version:  1.5.X        
 Keywords:              |  
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Comment(by nicklas):

 strk, you are right, pt_in_ring is counting crossings.

 As I understand now we have different point in polygon code in 4 places

 1) point_in_ring (winding number)
 2) pt_in_ring (crossing number)
 3) pt_in_ring_3d (winding number)
 4) There is also some implementation for geography somewhere (crossing
 number I think from a discussion some time ago)

 The geography implementation have to be separate of course.

 All the three others can be more or less merged.

 I have not studied winding number enough to understand it. But at the
 softsurfer link above that is what they recommend.

 My reason for rewriting the iterations in 3d-version even if it is the
 same thing happening as 2d-version is that it gets quite messy if I
 project the polygon to, say x-z plane instead of x-y since x and y is hard
 coded in the functions. If we can write the function so it just takes
 coord1 and coord2 instead of x and y it can be used more widely.

 How is that done in a robust way.

 In other words, is this possible to do in some efficient robust way?

 coord1=x;
 pt.coord1;

 instead of
 pt.x;

 a macro can do that?

 Will it be to ugly (unefficient) or is it worth it to share more code?

 /Nicklas

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/845#comment:11>
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