[postgis-devel] [PostGIS] #1176: [raster] Two raster ST_Intersects

[PostGIS]

#1176: [raster] Two raster ST_Intersects
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 Reporter:  dustymugs       |       Owner:  dustymugs    
     Type:  enhancement     |      Status:  assigned     
 Priority:  medium          |   Milestone:  PostGIS 2.0.0
Component:  postgis raster  |     Version:  trunk        
 Keywords:                  |  
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Comment(by pracine):

 From my point of view ST_Intersects should be a wrapper around the
 iterator part of the planned two raster version of mapalgebra.

 For this special case the iterator should be able to traverse all the
 raster pixels in a pseudo sequencial way (every 0 + 3 pixels on the first
 pass, every 1 + 3 pixels on the second pass and every 2 + 3 pixels on the
 third pass (this is different than sampling where skipped pixels are
 forgotten forever)) since we are searching for pixel having a certain
 characteristic and most nodata value pixels are generally neighbors. This
 is the technique used by ST_Intersects(raster, geometry) and it prooved
 much faster than a normal scan.

 For this special case, the iterator should also return as soon as both
 values are not nodata.

 I know this seems to be a nice case for Bryce's iterator but I still need
 a demonstration that this iterator is more simple/flexible/fast/useful
 than the iterator used in the two raster ST_MapAlgebra plpgsql prototype
 (not unnecessarily introducing the concept of mask by the way :-).

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1176#comment:14>
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