[postgis-users] Spatial operators

Luis Mota luis.mota at iscte.pt
Thu Oct 10 11:05:46 PDT 2002


That helped a lot.

Bye, Luís
Andy Turk wrote:

>I think this is beyond what Postgis will do for you. It's not a hard problem 
>though. What you want to know is whether three points are arranged in a 
>clockwise or counterclockwise fashion. The first two points being a line 
>segment in your linestring and the third being the point you're trying to 
>There's some straightfoward code for testing clockwiseness at 
>Look for the CCW function.

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