[postgis-users] ST_Mapalgebraexpr requires same alignment

[Jose Carlos Martinez]

Hi again, I still dont know why Im getting 'NOTICE:  The two rasters 
provided do not have the same alignment.  Returning NULL ' with
ST_Mapalgrebra. Im kind of stuck.

Any help would be appreciated.

On 22/03/2012 18:00, Jose Carlos Martinez wrote:
> Hi. Im trying to use mapalgebra between two layers with tiles, I get 
> this warning:
> NOTICE:  The two rasters provided do not have the same alignment.  
> Returning NULL
>
> The resulted tiles are empty. Does ST_Mapalgebraexpr  require same 
> alignment? According to the docs I guess not but then dont know why im 
> getting that message.
> In another example I didnt use st_union with the same result.
>
> insert into demdif (rast) select st_mapalgebraexpr (d1.rast, 1, 
> st_union (d2.rast),  1, 'abs([rast1.val] - [rast2-val])','16BSI', 
> 'FIRST', null, null,null) from dem200 d1, dem d2 where d1.rast && 
> d2.rast and st_relate (d1.rast::geometry, d2.rast::geometry, 
> 'T********') group by d1.rid;
>
> Another issue is st_union (internally is st_mapalgebraexpr) is 
> extremely slow. I can not manage raster layers bigger than a couple of 
> thousand pixel in x or y even with 128 tiled blocks.
>
> Jose
>
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