[postgis-users] PostGIS Raster Area from a Clip

[Marcello Benigno]

Hi All

I converted a raster to vector format, where the pixel values range from 1
to 8, then exported to PostGIS and made the following query:

   SELECT foo.value, ST_area(foo.geom::geography)
   FROM (
          SELECT c.value,
                 ST_Union(ST_Intersection(f.geom, c.geom)) as geom
          FROM fazendas f, capacidade_vect c
          WHERE  ST_Intersects(f.geom, c.geom)
          AND f.gid = 2
          GROUP BY c.value
          ORDER BY c.value
       ) AS foo;

I wonder if it is possible to obtain the same results using the table in
raster format (in this case *capacidade_rast*, not *_vect*), because as
described above takes too long. I'm complete newbie in PostGIS Raster...
Could anyone help me to build this query?

Thanks in advance,
-- 
*Marcello Benigno B. de Barros Filho*
Prof. do Curso Superior de Tecnologia em Geoprocessamento - IFPB
Mestre em Ciências Geodésicas e Tecnologias da Geoinformação - UFPE
Doutorando em Tecnologia Ambiental e Recursos Hídricos - UFPE
http://profmarcello.blogspot.com
http://about.me/marcello.benigno
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