[OSM-talk] osmxapi/bbox question

[Igor Brejc]

Karl Newman wrote:
> On Fri, Apr 11, 2008 at 5:47 AM, 80n <80n80n at gmail.com 
> <mailto:80n80n at gmail.com>> wrote:
>
>     You can have any shaped bbox you like as long as it is a rectangle ;)
>
>     Can anyone point me to a good algorithm for selecting points
>     within an arbitrary polygon?
>
>     80n
>
>
> I don't have it in pseudocode, but one I've heard of casts a ray 
> (horizontal is common) out from the point being tested and then checks 
> the intersection of that ray against each segment of the polygon. If 
> the total number of intersections is odd, then the point lies inside 
> the polygon. If the number is even, then it's outside. This works for 
> holes in a polygon, too.
>
> Karl
http://en.wikipedia.org/wiki/Point_in_polygon

Igor

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