[postgis-users] ST_Mapalgebraexpr requires same alignment

Jose Carlos Martinez jomarlla at cgf.upv.es
Fri Mar 23 09:32:18 PDT 2012

On 23/03/2012 17:12, Paul Ramsey wrote:
> On Fri, Mar 23, 2012 at 8:16 AM, Jose Carlos Martinez
> <jomarlla at cgf.upv.es>  wrote:
>> ummm...there is some plans about future releases to work with not alignment
>> rasters? to be honest I think this is a limitation in order to to carry out
>> a normal raster spatial analysis. :-(. I will try to use postgis raster
>> without this feature though.
> I don't think it's unreasonable to expect that inputs to mapalgebras
> be on the same alignment. I do thing that utilities for re-sampling
> whole tables need to exist to that it's possible to run full analyses
> inside the database, but I think requiring alignment for mapalgebra
> will solve more problems (in terms of people getting the results they
> "expect") than trying to plaster over it with automagical code.
I m not sure If i understand you because of english but what Im 100% 
sure is that any person who has made raster spatial analysis with real 
data knows that map algebra must work with raster with different 
alignment as other software do. The normal thing if I have raster layers 
from different sources is that they dont have same alignment, as I said 
so for any raster software that I know can work with these kind of data, 
thats why Im guessing PostGIS raster is working with pixels and not with 
terrain coordinates (but maybe Im wrong).

Please dont think in a computer science expertise way and think as if 
you were a geographer who just want to mix two raster layers and dont 
mind if they layers have same alignment or not. Otherwise people are 
going to keep using sextante, arcgis, grass, etc. instead of PostGIS Raster.

> P.
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