On Thu, 27 May 2010, Burton Shank wrote:
Hi all,
We're trying to process large amounts of remote-sensing data currently
stored in hdf v4 formats. I expect there may be a simple way to read these
files directly into R (ideally as a spatial pixels data frame) but can't
find the right function. It seems that it may be possible to use readGDAL
or readOGR but I can't find an appropriate syntax in the documentation.
Most people seem to pre-process these files into an hdf_5 or netDCS before
importing, and this would be acceptable except we're looking to process
hundreds of files and would rather avoid learning another scripting language
just for batch pre-processing. Are there any freeware programs that can
easily perform such batch-processing?
For a sample file, go to
http://oceandata.sci.gsfc.nasa.gov/SeaWiFS/Mapped/8Day/chlor/1997/
download any .bz2 file and unzip.
The unzipped files are in hd_4 format, though they don't have any file
extension (.hdf or .h4).
On a platform with GDAL built with the HDF4 driver, rgdal would cover
this, with some requirements with regard to the organisation of the data.
If the driver is not available, you could batch-convert to one of the
drivers that are available for rgdal for that platform. Since you do not
state your platform, I assume it is Windows. There, using for example an
OSGEO4W build of GDAL will probably include HDF4, but the Windows 32/64
bit builds of GDAL shipped with binary rgdal do not. So from R you would
use system() to call gdal_translate to get from HDF4 to say GTiff. On a
platform where you build your own GDAL, then install rgdal from source,
you should have the driver there for you:
http://www.gdal.org/frmt_hdf4.html
Hope this helps,
Roger
Any assistance is appreciated.
Burton Shank
Northeast Fisheries Science Center
Woods Hole, MA
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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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