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 <[EMAIL PROTECTED]>/* 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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