readGDAL() and HDF5 files
On Fri, 23 Jan 2009 11:01:21 +0100 (CET),
Roger Bivand <Roger.Bivand at nhh.no> wrote:
On Fri, 16 Jan 2009, Sebastian P. Luque wrote:
Hi,
I'm trying to use HDF5 files with this structure:
Sorry for the delay. Having now set up a reprodicable route (OSGeo4W GDAL and drivers, rgdal built against OSGeo4W as in a posting a couple of days ago), I can see the problem, but have no resolution.
Doing gdalinfo on the data itself, I see geographical coordinates, not projected. GDAL does not retrieve the grid metadata correctly, and assigns default 1x1 grid cells starting at c(0.5, 0.5). Using gdal_translate to convert it to a GTiff, I see that I have to set p4s to NA to read at all, and the problems remain. I would be interested in knowing who or what wrote the HDF5 file, because it doesn't seem to be what it says it is (no grid metadata, different CRS from your assumption), and so the data may actually be in the wrong order too.
Thanks for looking into this Roger. The data are distributed by the OSI-SAF group (http://www.osi-saf.org). I was able to work with the data using the NetCDF files they distribute (for a subset of their data for now), using NetCDF tools outside R. However, I'd like to do it more directly from R. In the NetCDF files, longitude, latitude, and the data, are stored in separate data subsets. The grid is produced using the CRS specification I provided (from OSI-SAF's documentation), however I cannot see where the actual coordinates in that projection are in the files. The geographical coordinates are the inverse-projected coordinates of the grid, hence not a regular grid. I might ask in the GDAL list for more help. Cheers,
Seb