The Geos Library has a method isCCW (counterclockwise) - ( http://geos.refractions.net/ro/doxygen_docs/html/classgeos_1_1algorithm_1_1CGAlgorithms.html ).
Unfortunately this algorithm is not exposed in the Geos C API (only the C++ API), and thus not available in the Python etc bindings - but the code is LGPL. HTH Ludwig 2008/5/29 Francisco R. Santos <[EMAIL PROTECTED]>: > > On Wed, May 28, 2008 at 10:26 PM, Richard Fairhurst <[EMAIL PROTECTED]> > wrote: > >> Can anybody point me in the direction of an algorithm that will >> determine whether a closed way (polyline) is clockwise or anti- >> clockwise? >> > > Take a look at this: > > > http://geometryalgorithms.com/Archive/algorithm_0101/algorithm_0101.htm#orientation2D_polygon()<http://geometryalgorithms.com/Archive/algorithm_0101/algorithm_0101.htm#orientation2D_polygon%28%29> > > Regards, > Quico > > > _______________________________________________ > dev mailing list > [email protected] > http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev > >
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