ST_SetM — Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the M dimension using the requested resample algorithm.
geometry ST_SetM(raster rast, geometry geom, text resample=nearest, integer band=1);
Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the M dimensions using the requested resample algorithm.
The resample parameter can be set to "nearest" to copy the values from the cell each vertex falls within, or "bilinear" to use bilinear interpolation to calculate a value that takes neighboring cells into account also.
Availability: 3.2.0
--
-- 2x2 test raster with values
--
-- 10 50
-- 40 20
--
WITH test_raster AS (
SELECT
ST_SetValues(
ST_AddBand(
ST_MakeEmptyRaster(width => 2, height => 2,
upperleftx => 0, upperlefty => 2,
scalex => 1.0, scaley => -1.0,
skewx => 0, skewy => 0, srid => 4326),
index => 1, pixeltype => '16BSI',
initialvalue => 0,
nodataval => -999),
1,1,1,
newvalueset =>ARRAY[ARRAY[10.0::float8, 50.0::float8], ARRAY[40.0::float8, 20.0::float8]]) AS rast
)
SELECT
ST_AsText(
ST_SetM(
rast,
band => 1,
geom => 'SRID=4326;LINESTRING(1.0 1.9, 1.0 0.2)'::geometry,
resample => 'bilinear'
))
FROM test_raster
st_astext
----------------------------------
LINESTRING M (1 1.9 38,1 0.2 27)