[postgis-users] Problem with overlay
mbdavis at refractions.net
Tue Jul 3 17:06:51 PDT 2007
Can you post the WKT of two linestrings which you think should overlap?
Overlaps has a very narrow definition. For Linestrings, two linestrings
overlap if and only if their intersection is itself a linestring (i.e.
they overlap in a point-set of dimension 1).
I suspect you may be seeing the result of the inevitable coordinate
drift caused by computing a new coordinate along a line segment. In
almost all cases, doing this results in two new line segments which are
NOT coincident with the original.
Jonathan Aguero wrote:
> That’s the point, they should /overlap/ since they were created from
> the same linear reference system and the road segment ‘/contains/’ the
> I also tried with /intersects/ but the problem is that it picks up
> more segments than I need. For example if a curve ends at the same
> point than a road segment; theoretically, the overlaps should pick up
> only that segment while /intersects/ pick also the following segment
> that starts when the previous segment ends. Think also in a situation
> where a road intersection is located in a curve: /intersects /will
> select the other segments that converge in the intersection even
> though they have no curves.
> Now, I might be misinterpreting what the overlap should do; if this is
> the case please let me know.
Senior Technical Architect
Refractions Research, Inc.
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