Hi, How can I perform ST_MapAlgebraExpr with raster layers that have different scale_x, scale_y. I suppose that the difference causes the two raster layers to be aligned differently
Joan On 22 November 2011 17:27, Bborie Park <[email protected]> wrote: > Joan (and anyone else using 2-raster MapAlgebra), > > You don't need to specify ::double precision in your expressions. > Under the hood, your expression is wrapped with parentheses and > ::double precision. So, if your expression was > > CASE WHEN rast2 > rast1 THEN rast1 ELSE rast2 END > > Internally, the expression becomes > > SELECT (CASE WHEN rast2 > rast1 THEN rast1 ELSE rast2 END)::double > precision > > -bborie > > On Tue, Nov 22, 2011 at 6:51 AM, Joan <[email protected]> wrote: > > I have tried it and it works. Thank you Pierre. > > > > On 22 November 2011 15:33, Pierre Racine <[email protected]> > > 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 > >> _______________________________________________ > >> postgis-users mailing list > >> [email protected] > >> http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > > > _______________________________________________ > > postgis-users mailing list > > [email protected] > > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > > > > > -- > Bborie Park > Programmer > Center for Vectorborne Diseases > UC Davis > 530-752-8380 > [email protected] > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users >
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