[R-sig-Geo] rgdal installation

[Michael Sumner]

Hello, to find which drivers are available to you in rgdal use 
gdalDrivers(). These won't be as many as are available in FWTools, 
unless you build rgdal from source against FWTools itself.  For HDF you 
must build rgdal against your own GDAL installation.

I've done this with VC++ - see the notes in rgdal/README.windows - it's 
fairly painful, and I haven't done it for several rgdal releases.
Far easier is to build GDAL and rgdal from source with msys, and I have 
detailed instructions provided by Roger Bivand that I could find.

But perhaps even simpler is to use gdal_translate  -  calls to this via 
system can be conveniently wrapped into a simple function to handle the 
georeferencing as well (which HDF rarely provides fully).  It is simply 
not possible to build a single rgdal to handle both HDF and netCDF, and 
so I have resorted to this method for such formats, rather than maintain 
2 separate rgdal builds.

I gather that your files are MODIS Terra SST, and so you still need to 
wrap the calls for reading since the georeferencing will not be 
available automatically, so I suggest that having access from rgdal will 
only give you slight benefit anyway.

Finally, if the files are composed of subdatasets (SDS) you would need 
to refer to that directly, rather than the file name.

This will tell you about the SDS:

gdalinfo T20060012006008.L3m_8D_NSST_9.hdf

This will give you access to the first SDS:

gdalinfo HDF4_SDS:UNKNOWN:"T20050172005024.L3m_8D_NSST_9.hdf":0

HTH

Cheers, Mike.


David PINAUD wrote:
> Dear all,
>
> I'm trying to import HDF (v4) files on R2.6.2  using the package rgdal 
> and FWTools v2.1.0. I have the following message :
>
> > GDALinfo("T20060012006008.L3m_8D_SST_9.hdf")
> Erreur dans .local(.Object, ...) :
>        GDAL Error 4: `T20060012006008.L3m_8D_SST_9.hdf' not recognised 
> as a supported file format.
>
> I can load this file with FWTools without problem.
> I suppose that rgdal is not able to recognize the path to the 
> FWTools/bin directory:
> > library(rgdal)
> Le chargement a nécessité le package : sp
> Geospatial Data Abstraction Library extensions to R successfully loaded
> Loaded GDAL runtime: GDAL 1.5.0, released 2007/12/18
> GDAL_DATA: C:/PROGRA~1/R/R-26~1.2/library/rgdal/gdal  ####### it 
> should be FWTools/bin ??  #####
> Loaded PROJ.4 runtime: Rel. 4.6.0, 21 Dec 2007
> PROJ_LIB: C:/PROGRA~1/R/R-26~1.2/library/rgdal/proj
>
> However I set before the PATH environment variable in Windows 
> (Start>Parameters>Configuration Panel>System>Advanced>Environment 
> variables : GDAL_DATA set to C:\Program Files\FWTools2.1.0\bin) as 
> explained in http://rgdal.sourceforge.net/. No effect.
>
> What's wrong ? Is there a thing that I've missed or didn't do 
> correctly? Is there another way to set this directory?
>
> Thank you for your help^.
>
> David
>
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