Changes between Version 163 and Version 164 of WKTRaster/SpecificationWorking03

Timestamp:

11/07/11 14:41:35 (13 years ago)

Author:

dustymugs

Comment:

—

WKTRaster/SpecificationWorking03

@@ -1438 +1438 @@
 
 ----
+
+== '''Objective FV.03 - ST_MapAlgebra (1 and 2 raster variants)''' ==
+
+'''Two raster ST_MapAlgebra'''
+
+These set of functions take two input rasters and create a 1-band output raster with the extent defined by extenttype.
+
+
+1. ST_MapAlgebra2Expr(
+        rast1 raster, band1 integer,[[BR]]
+        rast2 raster, band2 integer,[[BR]]
+        expression text,[[BR]]
+        pixeltype text DEFAULT NULL, extenttype text DEFAULT 'INTERSECTION',[[BR]]
+        nodata1expr text DEFAULT NULL, nodata2expr text DEFAULT NULL,[[BR]]
+        nodatanodataval double precision DEFAULT NULL
+) -> raster
+
+    rast1: the FIRST raster upon which a map algebra operation is to be done
+
+    band1: the band index (1-based) of the FIRST raster upon whose pixels a map algebra operation is to be done
+
+    rast2: the SECOND raster upon which a map algebra operation is to be done
+
+    band2: the band index (1-based) of the SECOND raster upon whose pixels a map algebra operation is to be done
+
+    expression: valid SQL expression resulting in a double precision value or NULL.  called when band 1 pixel AND band 2 pixel are NOT NODATA
+
+    pixeltype: the datatype of the output raster's one band
+
+    extenttype: one of the following (INTERSECTION, UNION, FIRST, SECOND)
+
+    nodata1expr: valid SQL expression resulting in a double precision value or NULL.  called when band 1 pixel IS NODATA and band 2 pixel IS NOT NODATA
+
+    nodata2expr: valid SQL expression resulting in a double precision value or NULL.  called when band 1 pixel IS NOT NODATA and band 2 pixel IS NODATA
+
+    nodatanodataval: double precision value used when band1 pixel and band 2 pixel are NODATA
+
+{{{
+ST_MapAlgebra2Expr(r1.rast, 1, r2.rast, 2, 'rast1', '32BF', 'INTERSECTION')
+
+ST_MapAlgebra2Expr(r1.rast, 1, r2.rast, 2, '((rast1 + rast2)/2.)::numeric', '32BF', 'UNION', 'rast2', 'rast1', NULL)
+
+ST_MapAlgebra2Expr(r1.rast, 1, r2.rast, 2, 'CASE WHEN rast2 IS NOT NULL THEN NULL ELSE rast1 END', '32BF', 'FIRST', NULL, 'rast1', NULL)
+
+ST_MapAlgebra2Expr(r1.rast, 1, r2.rast, 2, 'CASE WHEN rast1 IS NOT NULL THEN NULL ELSE rast2 END', '32BF', 'SECOND', 'rast2', NULL, NULL)
+}}}
+
+2. ST_MapAlgebra2Expr(
+        rast1 raster,[[BR]]
+        rast2 raster,[[BR]]
+        expression text,[[BR]]
+        pixeltype text DEFAULT NULL, extenttype text DEFAULT 'INTERSECTION',[[BR]]
+        nodata1expr text DEFAULT NULL, nodata2expr text DEFAULT NULL,[[BR]]
+        nodatanodataval double precision DEFAULT NULL
+) -> raster
+
+{{{
+ST_MapAlgebra2Expr(r1.rast, r2.rast, 'rast1', '32BF', 'INTERSECTION')
+
+ST_MapAlgebra2Expr(r1.rast, r2.rast, '((rast1 + rast2)/2.)::numeric', '32BF', 'UNION', 'rast2', 'rast1', NULL)
+
+ST_MapAlgebra2Expr(r1.rast, r2.rast, 'CASE WHEN rast2 IS NOT NULL THEN NULL ELSE rast1 END', '32BF', 'FIRST', NULL, 'rast1', NULL)
+
+ST_MapAlgebra2Expr(r1.rast, r2.rast, 'CASE WHEN rast1 IS NOT NULL THEN NULL ELSE rast2 END', '32BF', 'SECOND', 'rast2', NULL, NULL)
+}}}
+
+
+----
 == '''Objective FV.16 - Being able to quickly get raster statistics. - ''Done''''' ==