ST_HillShade — Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and scale inputs.
raster ST_HillShade(
raster rast, integer band=1, text pixeltype=32BF, double precision azimuth=315, double precision altitude=45, double precision max_bright=255, double precision scale=1.0, boolean interpolate_nodata=FALSE)
;
raster ST_HillShade(
raster rast, integer band, raster customextent, text pixeltype=32BF, double precision azimuth=315, double precision altitude=45, double precision max_bright=255, double precision scale=1.0, boolean interpolate_nodata=FALSE)
;
Returns the hypothetical illumination of an elevation raster band using the azimuth, altitude, brightness, and scale inputs. Utilizes map algebra and applies the hill shade equation to neighboring pixels. Return pixel values are between 0 and 255.
azimuth
is a value between 0 and 360 degrees measured clockwise from North.
altitude
is a value between 0 and 90 degrees where 0 degrees is at the horizon and 90 degrees is directly overhead.
max_bright
is a value between 0 and 255 with 0 as no brightness and 255 as max brightness.
scale
is the ratio of vertical units to horizontal. For Feet:LatLon use scale=370400, for Meters:LatLon use scale=111120.
If interpolate_nodata
is TRUE, values for NODATA pixels from the input raster will be interpolated using ST_InvDistWeight4ma before computing the hillshade illumination.
For more information about Hillshade, please refer to How hillshade works. |
Availability: 2.0.0
Enhanced: 2.1.0 Uses ST_MapAlgebra() and added optional interpolate_nodata
function parameter
Changed: 2.1.0 In prior versions, azimuth and altitude were expressed in radians. Now, azimuth and altitude are expressed in degrees
WITH foo AS ( SELECT ST_SetValues( ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '32BF', 0, -9999), 1, 1, 1, ARRAY[ [1, 1, 1, 1, 1], [1, 2, 2, 2, 1], [1, 2, 3, 2, 1], [1, 2, 2, 2, 1], [1, 1, 1, 1, 1] ]::double precision[][] ) AS rast ) SELECT ST_DumpValues(ST_Hillshade(rast, 1, '32BF')) FROM foo st_dumpvalues ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ ----------------------------------------------------------------------- (1,"{{NULL,NULL,NULL,NULL,NULL},{NULL,251.32763671875,220.749786376953,147.224319458008,NULL},{NULL,220.749786376953,180.312225341797,67.7497863769531,NULL},{NULL,147.224319458008 ,67.7497863769531,43.1210060119629,NULL},{NULL,NULL,NULL,NULL,NULL}}") (1 row)
Complete example of tiles of a coverage. This query only works with PostgreSQL 9.1 or higher.
WITH foo AS ( SELECT ST_Tile( ST_SetValues( ST_AddBand( ST_MakeEmptyRaster(6, 6, 0, 0, 1, -1, 0, 0, 0), 1, '32BF', 0, -9999 ), 1, 1, 1, ARRAY[ [1, 1, 1, 1, 1, 1], [1, 1, 1, 1, 2, 1], [1, 2, 2, 3, 3, 1], [1, 1, 3, 2, 1, 1], [1, 2, 2, 1, 2, 1], [1, 1, 1, 1, 1, 1] ]::double precision[] ), 2, 2 ) AS rast ) SELECT t1.rast, ST_Hillshade(ST_Union(t2.rast), 1, t1.rast) FROM foo t1 CROSS JOIN foo t2 WHERE ST_Intersects(t1.rast, t2.rast) GROUP BY t1.rast;