ST_Union — Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
raster ST_Union(
setof raster rast)
;
raster ST_Union(
setof raster rast, unionarg[] unionargset)
;
raster ST_Union(
setof raster rast, integer nband)
;
raster ST_Union(
setof raster rast, text uniontype)
;
raster ST_Union(
setof raster rast, integer nband, text uniontype)
;
Returns the union of a set of raster tiles into a single raster composed of at least one band. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by uniontype
which is one of the following: LAST (default), FIRST, MIN, MAX, COUNT, SUM, MEAN, RANGE.
In order for rasters to be unioned, they must all have the same alignment. Use ST_SameAlignment and ST_NotSameAlignmentReason for more details and help. One way to fix alignment issues is to use ST_Resample and use the same reference raster for alignment. |
Availability: 2.0.0
Enhanced: 2.1.0 Improved Speed (fully C-Based).
Availability: 2.1.0 ST_Union(rast, unionarg) variant was introduced.
Enhanced: 2.1.0 ST_Union(rast) (variant 1) unions all bands of all input rasters. Prior versions of PostGIS assumed the first band.
Enhanced: 2.1.0 ST_Union(rast, uniontype) (variant 4) unions all bands of all input rasters.
-- this creates a single band from first band of raster tiles -- that form the original file system tile SELECT filename, ST_Union(rast,1) As file_rast FROM sometable WHERE filename IN('dem01', 'dem02') GROUP BY filename;
-- this creates a multi band raster collecting all the tiles that intersect a line -- Note: In 2.0, this would have just returned a single band raster -- , new union works on all bands by default -- this is equivalent to unionarg: ARRAY[ROW(1, 'LAST'), ROW(2, 'LAST'), ROW(3, 'LAST')]::unionarg[] SELECT ST_Union(rast) FROM aerials.boston WHERE ST_Intersects(rast, ST_GeomFromText('LINESTRING(230486 887771, 230500 88772)',26986) );
Here we use the longer syntax if we only wanted a subset of bands or we want to change order of bands
-- this creates a multi band raster collecting all the tiles that intersect a line SELECT ST_Union(rast,ARRAY[ROW(2, 'LAST'), ROW(1, 'LAST'), ROW(3, 'LAST')]::unionarg[]) FROM aerials.boston WHERE ST_Intersects(rast, ST_GeomFromText('LINESTRING(230486 887771, 230500 88772)',26986) );