I have been trying to make a 16-bit geotiff. As I understand it, GDAL can do this. Is there any way to make grdimage do this? It seems to default to 8-bits.
I think you need to add /i16 or /ui16 after the driver name. See the -G option of grdconvert.
But on a second thought. grdimage creates only 8 bits (RGB) images so why would you want a 16 bits geotiff here?