[postgis-users] ST_Mapalgebra

[Joan]

I have tried it and it works. Thank you Pierre.

On 22 November 2011 15:33, Pierre Racine <Pierre.Racine at sbf.ulaval.ca>wrote:

> > I have used ST_MapAlgebraExpr but I get the error below.
> >
> >
> > select * from (select ST_MapAlgebraExpr(kb.rast, kb1.rast,
> 'kb1.rast+kb.rast') as
> > rast from kb_dsm_clip kb, kb_dsm_clip100 kb1) as r1 limit 5;
> > ERROR: missing FROM-clause entry for table "kb1"
> > LINE 1: SELECT (KB1.RAST+KB.RAST)::double precision ^
> > QUERY: SELECT (KB1.RAST+KB.RAST)::double precision
>
> Try this instead:
>
> SELECT ST_MapAlgebraExpr(kb.rast, kb1.rast, 'rast1 + rast2') as rast
> FROM kb_dsm_clip kb, kb_dsm_clip100 kb1
> WHERE st_intersects(kb.rast, kb1.rast)
>
> 1) There is no need for a subquery
>
> 2) You must refer to the raster using 'rast1' and 'rast2', not their real
> names
>
> 3) I don't know if your rasters are tiled but it is always a good idea to
> restrict the process to intersecting footprints.
>
> Pierre
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