[postgis-devel] [PostGIS] #1312: ST_MapAlgebraExpr mode UNION, incorrect Y-extent

[PostGIS]

#1312: ST_MapAlgebraExpr mode UNION, incorrect Y-extent
----------------------------+-----------------------------------------------
 Reporter:  tilt            |       Owner:  pracine      
     Type:  defect          |      Status:  new          
 Priority:  high            |   Milestone:  PostGIS 2.0.0
Component:  postgis raster  |     Version:  1.5.X        
 Keywords:                  |  
----------------------------+-----------------------------------------------
 When using ST_MapAlgebraExpr in UNION mode, the expected behavior is to
 return the minimum lower Y coordinate and maximum upper Y coordinate of
 both rasters.
 Instead, for the lowest upper Y is returned and for lower Y a value even
 below the lowest.

 If this sounds confusing, just check the output of this code:

 {{{

 WITH
  raster1 As (
         SELECT ST_MakeEmptyRaster( 100, 100, 19000, 40000, 1, -1, 0, 0,
 28992) As rast
         )
  ,raster2 As (
         SELECT ST_MakeEmptyRaster( 100, 100, 19200, 40200, 1, -1, 0, 0,
 28992) As rast
         )
 , combi As (
 SELECT
         ST_MapAlgebraExpr(
                 raster1.rast,
                 raster2.rast,
                 'rast1+rast2',
                 NULL,
                 'UNION'
                 ) As rast
 FROM
         raster1, raster2
         )

 SELECT
         ST_Ymin(ST_Envelope(raster1.rast)),
         ST_Ymax(ST_Envelope(raster1.rast)),
         ST_Ymin(ST_Envelope(raster2.rast)),
         ST_Ymax(ST_Envelope(raster2.rast)),
         ST_Ymin(ST_Envelope(combi.rast)),
         ST_Ymax(ST_Envelope(combi.rast))
 FROM raster1, raster2, combi;
 }}}

 Output:
 {{{
 39900;40000;40100;40200;39700;40000
 }}}

 EXPECTED output:
 {{{
 39900;40000;40100;40200;39900;40200
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1312>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.