[postgis-users] sum the values of overlapping polygons

[Greg Allensworth]

You could take the union of them, which would merge the overlapping areas.

SELECT ST_AREA(
    (SELECT ST_UNION(geom) FROM table WHERE whatever=whatever)
) AS area;

Your resulting units would be the same as your projection, e.g. square 
degrees. So you may want to convert to an SRS that preserves area, e.g. 
Albers.

SELECT ST_AREA(ST_TRANSFORM(
    (SELECT ST_UNION(geom) FROM table WHERE whatever=whatever)
    ,
    3083
) AS area;


-g


On 7/2/2014 9:47 AM, Alessandro De Martino wrote:
> Hi,
> I am looking for a way to sum the values of overlapping polygons.
> I have a polygon shapefile with thousands of records and I need to know
> how to sum the values of the polygons when they overlap.
> Thanks!
>
>
>
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>


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Greg Allensworth, Senior Web GIS Developer
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