[gdal-dev] HDF subdatasets

[Frank Warmerdam]

Bobby Braswell wrote:
> 
> Hi-
> 
> Is it possible to access the names of subdatasets in HDF4 files using 
> gdal-python? I can get the SDS names using gdalinfo, but would like to 
> do it from within my code.
> 
> For example the result of
> 
> D = gdal.Open('MCD43A4.A2002001.h18v01.005.2007115060137.hdf')
> 
> produces some dictionaries within D containing metadata information, but 
> I can't find the subdataset names anywhere, e.g.,
> 
> 'HDF4_EOS:EOS_GRID:"MCD43A4.A2002001.h18v01.005.2007115060137.hdf":Nadir_Reflectance_Band1' 


Bobby,

You should be able to fetch the subdataset metadata using:

  sdlist = D.GetMetadata( 'SUBDATASETS' )

eg.

 >>> import gdal
 >>> D = gdal.Open('NISE_SSMIF11_19911227.HDFEOS')
GDAL: GDALOpen(NISE_SSMIF11_19911227.HDFEOS) succeeds as HDF4.
 >>> print D.GetMetadata('SUBDATASETS')
{'SUBDATASET_2_NAME': 
'HDF4_EOS:EOS_GRID:"NISE_SSMIF11_19911227.HDFEOS":Northern Hemisphere:Age', 
'SUBDATASET_4_DESC': '[721x721] Age Southern Hemisphere (8-bit unsigned 
integer)', 'SUBDATASET_4_NAME': 
'HDF4_EOS:EOS_GRID:"NISE_SSMIF11_19911227.HDFEOS":Southern Hemisphere:Age', 
'SUBDATASET_3_NAME': 'HDF4_EOS:EOS_GRID:"NISE_SSMIF11_19911227.HDFEOS":Southern 
Hemisphere:Extent', 'SUBDATASET_2_DESC': '[721x721] Age Northern Hemisphere 
(8-bit unsigned integer)', 'SUBDATASET_1_DESC': '[721x721] Extent Northern 
Hemisphere (8-bit unsigned integer)', 'SUBDATASET_3_DESC': '[721x721] Extent 
Southern Hemisphere (8-bit unsigned integer)', 'SUBDATASET_1_NAME': 
'HDF4_EOS:EOS_GRID:"NISE_SSMIF11_19911227.HDFEOS":Northern Hemisphere:Extent'}

Note, the return value is a dictionary with keys of the form
SUBDATASET_n_NAME and SUBDATASET_n_DESC.

You might also want to skim the portion of

   http://www.gdal.org/gdal_datamodel.html

with the subtitle "SUBDATASETS Domain".

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org