[gdal-dev] Accessing to a NetCDF subdataset with Python

[Paolo Corti]

Hi list

I am with GDAL 1.10.
I thought it was possible to access to a netCDF subdataset in the
usual manner (using GetRasterBand), but it does not seem to work in my
local box:

>>> from osgeo import gdal
>>> from osgeo.gdalconst import *
>>> gdal.AllRegister()
>>> file_nc = 'NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc"'
>>> ds = gdal.Open(file_nc, GA_ReadOnly)
>>> ds.RasterCount
0

while, using the subdataset name access syntax, it is working:

>>> from osgeo import gdal
>>> from osgeo.gdalconst import *
>>> gdal.AllRegister()
>>> file_nc = 'NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":area'
>>> ds = gdal.Open(file_nc, GA_ReadOnly)
Warning 1: Latitude grid not spaced evenly.
Seting projection for grid spacing is within 0.1 degrees threshold.
>>> ds.RasterCount
1

Now, do I have a local problem, or the second way is the only way to
access to a subdataset?
And in such a case, is the only way to programmatically access to the
subdatasets by reading their name using GetSubdataset or there is a
better way?

>>> ds.GetSubDatasets()
[('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":area', '[128x256] area
(32-bit floating-point)'),
('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":lat_bnds', '[128x2]
lat_bnds (64-bit floating-point)'),
('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":lon_bnds', '[256x2]
lon_bnds (64-bit floating-point)'),
('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":msk_rgn', '[128x256]
msk_rgn (32-bit integer)'),
('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":pr', '[1x128x256]
precipitation_flux (32-bit floating-point)'),
('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":tas', '[1x128x256]
air_temperature (32-bit floating-point)'),
('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":time_bnds', '[1x2]
time_bnds (64-bit floating-point)'),
('NETCDF:"sresa1b_ncar_ccsm3_0_run1_200001.nc":ua', '[1x17x128x256]
eastward_wind (32-bit floating-point)')]
>>> sds = gdal.Open(ds.GetSubDatasets()[0][0])

thanks in advance!
p

-- 
Paolo Corti
Geospatial software developer
web: http://www.paolocorti.net
twitter: @capooti
skype: capooti