[gdal-dev] [gdal_translate] Spatial subset HDF4Image with multiple subdatasets?

[Vincent Schut]

On 06/20/2012 02:55 PM, Etienne Tourigny wrote:
> You could combine them as a multi-band gtiff file for example
No, in this case (MOD09GA data) you cannot, because the subdatasets have 
different resolutions / raster sizes, and datatypes. Imho there is no 
other way than to subset each subdataset separately. Things might seem a 
bit more logical when you consider the main hdf file as a container, 
like a directory or an archive. You also cannot subset a directory, but 
you'll need to subset each raster file in it by itself.

Best,
Vincent.

>
> On Wed, Jun 20, 2012 at 9:50 AM, dcd <dennis.duro at glel.carleton.ca> wrote:
>> Le mardi 19 juin 2012 23:55:49, dcd a écrit :
>>> Hi,
>>>
>>> Is it possible to spatially subset an HDF4Image that contains multiple
>>> subdatasets using gdal_translate (GDAL 1.9.1)? When using a spatial subset
>>> switch ("-a_ullr"), I get the following response:
>>>
>>> "Input file contains subdatasets. Please, select one of them for reading."
>>>
>>> This happens regardless of output format specified (HDF4Image, GTiff,
>>> ENVI,
>>> etc.), or whether the "-b" switch has been used as per the examples here:
>>> http://www.gdal.org/gdal_translate.html. A workaround is to use the "-sds"
>>> switch allows the process to complete, but (as expected) it processes each
>>> subdataset as a separate file. I suppose I can just merge these
>>> subdatasets
>>> together again, but I'd like to avoid the extra step. Is this possible?
>>>
>>> I'm working with a MODIS imagery (MOD09GA), but I've had the issues with
>>> other similar HDF4 datasets.
>> You can use one of the subdataset names listed by gdalinfo on the HDF file
>> as a
>> pseudo-filename usable by any GDAL utility (including gdal_translate).
>>
>> For example :
>>
>> $ gdalinfo MOD02HKM.A2011169.1750.005.NRT.hdf
>> [...]
>> Subdatasets:
>>
>> SUBDATASET_1_NAME=HDF4_EOS:EOS_SWATH:"MOD02HKM.A2011169.1750.005.NRT.hdf":MODIS_SWATH_Type_L1B:EV_500_RefSB
>>   SUBDATASET_1_DESC=[5x4060x2708] EV_500_RefSB MODIS_SWATH_Type_L1B (16-bit
>> unsigned integer)
>>
>> SUBDATASET_2_NAME=HDF4_EOS:EOS_SWATH:"MOD02HKM.A2011169.1750.005.NRT.hdf":MODIS_SWATH_Type_L1B:EV_500_RefSB_Uncert_Indexes
>>   SUBDATASET_2_DESC=[5x4060x2708] EV_500_RefSB_Uncert_Indexes
>> MODIS_SWATH_Type_L1B (8-bit unsigned integer)
>> [...]
>>
>> $ gdalinfo
>> HDF4_EOS:EOS_SWATH:"MOD02HKM.A2011169.1750.005.NRT.hdf":MODIS_SWATH_Type_L1B:EV_500_RefSB
>>
>> Driver: HDF4Image/HDF4 Dataset
>> Files: MOD02HKM.A2011169.1750.005.NRT.hdf
>> Size is 2708, 4060
>> Coordinate System is `'
>> GCP Projection =
>> GEOGCS["WGS 84",
>>     DATUM["WGS_1984",
>>         SPHEROID["WGS 84",6378137,298.257223563,
>>             AUTHORITY["EPSG","7030"]],
>>         TOWGS84[0,0,0,0,0,0,0],
>>         AUTHORITY["EPSG","6326"]],
>>     PRIMEM["Greenwich",0,
>>         AUTHORITY["EPSG","8901"]],
>>     UNIT["degree",0.0174532925199433,
>>         AUTHORITY["EPSG","9108"]],
>>     AUTHORITY["EPSG","4326"]]
>> [...]
>> _______________________________________________
>>
>> Merci beaucoup for the quick reply!
>>
>> Sorry, I didn't mention in the original post that I need to spatially subset
>> hundreds of images.
>>
>> While I know that I can declare subdatasets individually, it will still mean
>> that I need to combine the individual subdatasets after spatial subsetting.
>> Also, declaring individual subdatasets by name is a bit of pain, although
>> doable if need be.
>>
>> It would be nice if the "-b" switch in gdal_translate could be used for
>> selecting specific subdatasets within an HDF4Image, either by their full
>> name (SUBDATASET_1_NAME=....), description (SUBDATASET_1_DESC=...), or
>> preferably by index ("-b 1" would be equivalent to "SUBDATASET_1", "-b 2"
>> would be equivalent to "SUBDATASET_2", etc). When reading the gdal_translate
>> documentation for the "-b" switch, it appears that this should be possible,
>> although the example is with a GTiff image. If it is possible with HDF
>> files, I'd like to know how. If not, I will put in a request using the
>> appropriate channels.
>>
>> I could always use the MODIS Reprojection Tool to script this task, but I'd
>> like to have done this exclusively using GDAL.
>>
>> Anyway, thanks for the tip!
>>
>>
>>
>> --
>> View this message in context: http://osgeo-org.1560.n6.nabble.com/gdal-translate-Spatial-subset-HDF4Image-with-multiple-subdatasets-tp4982526p4982668.html
>> Sent from the GDAL - Dev mailing list archive at Nabble.com.
>> _______________________________________________
>> gdal-dev mailing list
>> gdal-dev at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev