[postgis-devel] [PostGIS] #590: [raster] Two rasters version of ST_MapAlgebra

[PostGIS]

#590: [raster] Two rasters version of ST_MapAlgebra
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 Reporter:  pracine         |       Owner:  dustymugs    
     Type:  task            |      Status:  assigned     
 Priority:  critical        |   Milestone:  PostGIS 2.0.0
Component:  postgis raster  |     Version:  trunk        
 Keywords:                  |  
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Comment(by dustymugs):

 > The question we have to solve, since this is specific to raster, is
 "Should we resample implicitely when needed?" This is also the first time
 we are facing the issue since this is the first function involving two
 rasters (the question should have raised for ST_Intersects(raster, raster)
 however. Bborie, does that mean that it is possible for two rasters being
 resampled differently to return a different result for ST_Intersects()?).
 For sure there should be a warning if implicit resampling is performed.
 >

 For the ST_Intersects() function, the alignment of the two rasters do not
 matter.  Only the SRID must be the same.  This is because ST_Intersects
 uses the grid/pixel lines and sees where they intersect.  So being aligned
 and resampling is unnecessary.

 As for your question "does that mean that it is possible for two rasters
 being resampled differently to return a different result for
 ST_Intersects()?", no.  Whatever resampling is done, the output resampled
 raster's extent would contain the entirety of the input raster.

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/590#comment:17>
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