[postgis-users] Effectively combining rasters

[Pierre Racine]

What if you store the two bands in the same raster?

Pierre

> -----Original Message-----
> From: postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-
> bounces at lists.osgeo.org] On Behalf Of Kim Bisgaard
> Sent: Tuesday, November 27, 2012 8:17 AM
> To: postgis-users at postgis.refractions.net
> Subject: [postgis-users] Effectively combining rasters
> 
> Hi,
> 
> I am trying to combine rasters, or in other words pick a value at a position in one
> raster and at the same time get the value at same the
> same position in the other raster. The way I'm doing it, takes a long time
> compare to only picking values from one raster, which makes me
> think that there ought to be a more efficient way?
> 
> I am currently using this SQL:
> select st_x(st_centroid((AA).geom)) as lon,
>         st_y(st_centroid((AA).geom)) as lat,
>         (AA).val as "AAA",
>         (BB).val as "BBB"
> from (select st_intersection(A.rast,1,pos.geom) as AA,
>               st_intersection(B.rast,1,pos.geom) as BB
>        from (select ST_GeomFromText('MULTIPOLYGON(((15.000 54.800,15.000
> 55.000,14.800 55.000,14.800 54.800,15.000 54.800)))',4326) as geom)
> as pos join
>             A on st_intersects(A.rast,pos.geom) join
>             B on st_intersects(B.rast,pos.geom) ) as foo
> where (AA).geom = (BB).geom
> order by lon, lat;
> 
> As a side note I can tell that both rasters are equal in geographical sense
> (different bands from the same data).
> 
> Looking in 2 rasters takes 1.4 sec. and in one raster is 60ms
> 
> This is PostgreSQL 9.1.6, PostGIS 2.0.1
> 
> Thanks in advance!
> 
> Regards,
> 
> --
> Kim Bisgaard
> 
> Application Development Division     Phone: +45 3915 7562 (direct)
> Danish Meteorological Institute      Fax: +45 3915 7460 (division)
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