ST_UpperLeftX — Returns the upper left X coordinate of raster in projected spatial ref.
float8 ST_UpperLeftX(raster rast);
Returns the upper left X coordinate of raster in projected spatial ref.
SELECt rid, ST_UpperLeftX(rast) As ulx
FROM dummy_rast;
rid | ulx
-----+------------
1 | 0.5
2 | 3427927.75