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Re: 950313: HDF & netCDF

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  • Subject: Re: 950313: HDF & netCDF
  • Date: Mon, 13 Mar 1995 09:25:42 -0700
>Organization:Cente for Global Atmospheric Modelling, University of Reading 
>Keywords: 199503131254.AA14609

Hi Ian,

> I've been running through the FAQ and User Guide made available on your FTP 
> server in order to judge whether to use HDF or netCDF formats as the standard 
> output for a coupled ocean-atmosphere model. HDF is currently used by a 
> research group working in parallel on the ocean component with whom a large 
> amount of collaborative work is envisaged while much of the visualisation 
> software for the atmosphere component uses netCDF.
> 
> The ideal solution would be to be able to read HDF format files from the 
> collaborative group and use the netCDF visualisation software. If the current
> version of netCDF is used, will it be able to read HDF files? 

No, our netCDF software will not read HDF files.  It's not clear to me what
it would mean to be able to read non-netCDF HDF-encoded data with the netCDF
interface.  NetCDF and HDF are not just two different formats for the same
underlying data, they are two different models for how data should be
accessed and represented..

However, the NCSA HDF software does include a library (mfhdf) that permits
using the netCDF interface to read and write data using the netCDF model.
If you have sources for the netCDF-based visualization software, one partial
solution is to relink it with the HDF mfhdf library.  This would make the
visualization software capable of reading netCDF data that had been written
with either the HDF netCDF interface (HDF-encoded netCDF data) or the
Unidata netCDF software (XDR-encoded netCDF data).  This would not permit
the visualization software to read other kinds of HDF data written with
other HDF interfaces, however.

In addition to the mfhdf library that permits reading XDR-encoded netCDF
data or HDF-encoded netCDF data into a program, software is also available
to convert XDR-encoded netCDF files to HDF-encoded netCDF files and
vice-versa ("ncdump file | ncgen -" using ncdump from one package and ncgen
from the other).

The problem of converting HDF-encoded non-netCDF data into netCDF data is
not very well-defined, and I know of no software that attempts this
conversion.

There are several visualization packages that can be used to browse through
both HDF and netCDF files, for example DDI, IDL, Envision, the IBM
Visualization Data Explorer, PV-Wave, the SGI Iris Explorer, SciAn, etc.
For more detailed descriptions of these packages and references to more
information about them, see the WWW document

    http://www.unidata.ucar.edu/packages/netcdf/utilities.html 

or the text version of it available by anonymous FTP from 

    ftp://ftp.unidata.ucar.edu/pub/netcdf/utilities.txt

______________________________________________________________________________

Russ Rew                                                UCAR Unidata Program
address@hidden                                          P.O. Box 3000
http://www.unidata.ucar.edu/                          Boulder, CO 80307-3000
______________________________________________________________________________