[postgis-users] area resulting from ST_Within

[Fred Lehodey]

Hi Surya,
you can try something like that:

SELECT ws.name,dt.name,
sum(ST_area(ST_intersection(ws.the_geom,dt.the_geom)))
FROM  watersheds as ws, districts as dt
WHERE ST_intersects(ws.the_geom,dt.the_geom)
GROUP BY ws.name,dt.name
ORDER BY dt.name

Fred.




On Sun, Sep 21, 2008 at 3:37 AM, surya <storma-ipb at indo.net.id> wrote:

> Dear List,
>
> I have two  tables, one table contains   5 polygons depicting 5 watersheds
> or river basin boundaries. Another table contain district bondaries. Using
> ST-contain function below, I have obtained districts belong to a certain
> watershed . My qestion is how to calculate area of each district contained
> in a certain watershed using sum(area)(), taking into consideration that one
> district might be splitted in two or more different watershed
>
> SELECT watersheds.name, districts.name
> FROM watersheds, districts
> WHERE ST_contains (watersheds.the_geom, districts.the_geom)
> GROUP BY watersheds.name, districts.name ;
>
> best regards,
>
> surya
>
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