Compute partial polygon area

[Stephen Woodbridge]

Get the windows installer that Greg mentioned or there is also a French 
site http://techer.pascal.free.fr/postgis/ which has packages also.

-Steve

Krung Saengpole wrote:
> Hi Steve,
>  
> Thank you for your reply. I'll try it but may take so long time. I used 
> to try postGIS, but grant problem came to me. Could you please pointing 
> me to the right place to start playing with postGIS on Windows?
> Thank you again.
> Krung
> */Stephen Woodbridge <woodbri at swoodbridge.com>/* wrote:
> 
>     Krung Saengpole wrote:
>      > Hi all,
>      >
>      > I'd like to compute partial area of polygon that intersects with
>     another
>      > polygon. Is there a way to do with PHPMapscript? For example, I
>     want to
>      > know how many square kilometers of forests that reside in the
>     area of
>      > 50km-radius circled area. Or where can I get to the example?
> 
>     If you use PostGIS this is a straight forward SQL query like:
> 
>     select polyid, area2d(intersection(the_geom, circleAsPolygon(point(x,
>     y), radius, npoints)) as area from mytable where the_geom &&
>     expand(point(x, y), radius);
> 
>     where the_geom is the geometry column for the polygons
>     and x,y is the center of your circle radius = 50000
>     and npoints is the number of points to generate for the polygonal
>     circle.
> 
>     you would need to write a function circleAsPolygon() in pgsql, but that
>     is pretty trivial and most of us that would with PostGIS could post
>     that
>     if you needed us to.
> 
>     -Steve
> 
> 
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