Dear Fred,
Thank you very much. It works correctly !!. I try to further convert the area
of each district in a watershed as percentage to the watershed area in
question. Please give me more help.
best regards,
surya
----- Original Message -----
From: Fred Lehodey
To: PostGIS Users Discussion
Sent: Sunday, September 21, 2008 4:35 PM
Subject: Re: [postgis-users] area resulting from ST_Within
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 <[EMAIL PROTECTED]> 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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