[geos-devel] Re: [GEOS] #323: A point interpolated from a line does not always intersect the same line

[GEOS]

#323: A point interpolated from a line does not always intersect the same line
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 Reporter:  starsareblue  |        Owner:  geos-devel at lists.osgeo.org
     Type:  defect        |       Status:  reopened                  
 Priority:  major         |    Milestone:                            
Component:  Default       |      Version:  3.2.0                     
 Severity:  Unassigned    |   Resolution:                            
 Keywords:                |  
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Comment (by sgillies):

 Roy, are you certain you don't have a coordinate mixup in your code?

 The situation is a multilinestring consisting of 2 perpendicular lines
 that cross at (0,1), right? Interpolating (via Shapely) gives me a result
 that I expect: as the normalized length approaches 0.5, the interpolated
 point approaches (0, 0), the end of the first linestring. Go past length
 0.5 and there's a jump to (-1, 1), the starting point of the second
 linestring.

 I'm not seeing any wrap-around when the normalized length > 1: I always
 get the end of the second linestring. But with normalized length < 0, the
 interpolation appears to go in reverse, starting from the end of the
 second linestring and working its way back to the start of the first
 linestring.

 Paul, that's an intended feature, right?

-- 
Ticket URL: <http://trac.osgeo.org/geos/ticket/323#comment:5>
GEOS <http://geos.refractions.net/>
GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology Suite (JTS).