PostGIS
Name
ST_NearestValue — Returns the nearest non-NODATA value of a given
band’s pixel specified by a columnx and rowy or a geometric point
expressed in the same spatial reference coordinate system as the raster.
Synopsis
double precision +`*`+ST_NearestValue*(`raster `rast, integer
bandnum, geometry pt, boolean
exclude_nodata_value=true`)`;
double precision +`*`+ST_NearestValue*(`raster `rast, geometry
pt, boolean exclude_nodata_value=true`)`;
double precision +`*`+ST_NearestValue*(`raster `rast, integer
bandnum, integer columnx, integer rowy, boolean
exclude_nodata_value=true`)`;
double precision +`*`+ST_NearestValue*(`raster `rast, integer
columnx, integer rowy, boolean
exclude_nodata_value=true`)`;
Description
Returns the nearest non-NODATA value of a given band in a given
columnx, rowy pixel or at a specific geometric point. If the columnx,
rowy pixel or the pixel at the specified geometric point is NODATA,
the function will find the nearest pixel to the columnx, rowy pixel or
geometric point whose value is not NODATA.
Band numbers start at 1 and bandnum is assumed to be 1 if not
specified. If exclude_nodata_value is set to false, then all pixels
include nodata pixels are considered to intersect and return value.
If exclude_nodata_value is not passed in then reads it from metadata
of raster.
Availability: 2.1.0
|
Examples
-- pixel 2x2 has value
SELECT
ST_Value(rast, 2, 2) AS value,
ST_NearestValue(rast, 2, 2) AS nearestvalue
FROM (
SELECT
ST_SetValue(
ST_SetValue(
ST_SetValue(
ST_SetValue(
ST_SetValue(
ST_AddBand(
ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
'8BUI'::text, 1, 0
),
1, 1, 0.
),
2, 3, 0.
),
3, 5, 0.
),
4, 2, 0.
),
5, 4, 0.
) AS rast
) AS foo
value | nearestvalue
-------+--------------
1 | 1-- pixel 2x3 is NODATA
SELECT
ST_Value(rast, 2, 3) AS value,
ST_NearestValue(rast, 2, 3) AS nearestvalue
FROM (
SELECT
ST_SetValue(
ST_SetValue(
ST_SetValue(
ST_SetValue(
ST_SetValue(
ST_AddBand(
ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
'8BUI'::text, 1, 0
),
1, 1, 0.
),
2, 3, 0.
),
3, 5, 0.
),
4, 2, 0.
),
5, 4, 0.
) AS rast
) AS foo
value | nearestvalue
-------+--------------
| 1