See this tutorial:
http://trac.osgeo.org/postgis/wiki/WKTRasterTutorial01
search for "Intersecting the caribou buffers with the elevation rasters"
the query look like this:
CREATE TABLE resulttable AS
SELECT id,
(gv).geom AS the_geom,
(gv).val
FROM (SELECT id,
ST_Intersection(rast, the_geom) AS gv
FROM yourrastertable,
yourpolygontable
WHERE ST_Intersects(rast, the_geom)
) foo;
Then you have to summarize the results like this:
CREATE TABLE finalresult AS
SELECT id,
sum(ST_Area(the_geom) * val) /
sum(ST_Area(the_geom))) AS meanelev
FROM resulttable
GROUP BY id
ORDER BY id;
>-----Original Message-----
>From: [email protected] [mailto:postgis-users-
>[email protected]] On Behalf Of AJ7
>Sent: 14 mars 2011 13:13
>To: [email protected]
>Subject: [postgis-users] postgis raster : getting pixel value
>
>
>Hi,
>Is it possible to get the pixel value(s) out of the raster image once its
>been exported to postgis raster?
>
>Basically what I want to do is find the pixel values for all the pixels that
>intersect with a different polygon.
>
>Not sure if ST_value will help do that.
>tahnks
>--
>View this message in context:
>http://old.nabble.com/postgis-raster-%3A-getting-pixel-value-
>tp31146394p31146394.html
>Sent from the PostGIS - User mailing list archive at Nabble.com.
>
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