[postgis-users] MapAlgebra on three Rasters

JamesH james.holmes at newcastle.ac.uk
Thu Apr 26 06:50:49 PDT 2012

I have refined my query so that I am using MapAlgebraExpr on the normalised
distance and density rasters and exporting as a new table.
Then I am using a second, new MapAlgerbaExpr query with this table and the
normalised slope surface.

However it is returning, 'The two rasters provided do not have the same
alignment.  Returning NULL'. Looking at the documentation, I tried
ST_Resample the slope raster before passing it to the MapAlgebraExpr, using
the table from the first MapAlgebra as the Resample reference.

The query ran but this new Raster returned as empty. Can anyone explain why?

Current query is:
CREATE TABLE Metro_location AS(

b.rast), 1, b.rast, 1, '([rast1] * 0.2) + [rast2]', '32BF') as rast, 1 as
	Slope a, DensDist b

Kind Regards,

GIS Undergraduate
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