[Gdal-dev] How to add a NODATA flag to GTiff data?

[Thom DeCarlo]

Hello,
I've got several IFSAR DEM files in geotiff format. Each has a border of
NODATA values (-9999.0) around the real data. My OpenSceneGraph application
(osgdem, which uses gdal to read the input data) should understand that the
default NODATA value is -9999, but it uses that value instead of ignoring
it. 

I remember that when I translated ArcGrid data, which had NODATA values
defined in the header, to geotiff the output had a NODATA field in the
header. My question now is how do I add the NODATA field to the geotiff file
when translating from geotiff or Erdas Imagine format?

Thanks,
Thom