Jesse,
the answer lies in exploring available Spatialite SQL functions:
https://www.gaia-gis.it/gaia-sins/spatialite-sql-5.1.0.html
ST_Centroid() returns a Point geometry. You may get its coordinates with
ST_X() and ST_Y(). I suppose you'd need to use a sub-select construct to
get things working, like
SELECT gdal_get_pixel_value(path, band_num, 'georef', ST_X(centroid),
ST_Y(centroid)) FROM (SELECT ST_Centroid(geometry) AS centroid FROM ds) x
untested obviously!
Le 08/05/2024 à 19:09, Meyer, Jesse R. (GSFC-618.0)[SCIENCE SYSTEMS AND
APPLICATIONS INC] via gdal-dev a écrit :
Hi,
I’m wanting to execute a SQL query on a vector database like:
vector_mem_ds.ExecuteSQL(/f/"select ST_Centroid(GEOMETRY) as cnt,
gdal_get_pixel_value('{raster_fp}', {ndvi_band_num}, 'georef',
cnt.STX, cnt.STY) from ds",/dialect/="SQLITE")
In particular, I want to use the geometry’s centroid for
gdal_get_pixel_value, but the latter function takes two parameters,
and ST_Centroid provides 1 return value (a compound type Point), so I
am hoping for some way to unpack this into the form necessary expected
from get_pixel_value. Apparently some GIS query engines do expose a
STX and STY field but that’s if you trust random google results. But
as is this fails.
Is this possible largely as-is?
Thanks,
Jesse
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