[postgis-users] Spatial operators

[Luis Mota]

Thanks.

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 
>locate.
>
>There's some straightfoward code for testing clockwiseness at 
>http://support.microsoft.com/default.aspx?scid=kb;EN-US;q121960
>
>Look for the CCW function.
>