[geos-devel] how to know if two linestrings "really" cross each other

[Jasmin FORMONT]

Hi everyone

I can't find a way to tell if two linestrings "really" cross each other.

For instance if I have this linestring :
Line1 : LINESTRING(0 0, 1 1, 2 0)

How can I differentiate the relation of line 1 with one of the following :
Line2 : LINESTRING(0 2, 1 1, 2 2)    -> no "real" cross, just a contact point
Line3 : LINESTRING(0 2, 1 1, 1 0)    -> lines "really" cross each other

I can't find a good combination of crosses, touches, etc... to differentiate these cases.

Thanks in advance
Jasmin



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