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Re: HDF file format



Hi Frank,

There are two ways to handle HDF files from Ferret.

  1. Install a DODS HDF server (see
     http://unidata.ucar.edu/packages/dods/).  This will make the files
     "look like" netCDF to Ferret.  The filename becomes a URL pointing
     to the DODS server.
  2. Relink Ferret with the HDF version of the netCDF libraries.

Both of the answers are simplifications. (If someone more expert than I
in HDF would care to correct my errors here please chime in!) HDF is a
name for a long history of file definition evolution at NCSA.
Underneath that name are at least three fairly distinct API's and
associated file types: The "SDS" API is essentially netCDF and the above
suggestions should work for those files. There is an old raster standard
for images embedded into HDF. And there is also the Vset API which
creates hierarchal structures. Solution 1 (DODS) will work for many
aspects of these other APIs but definitely not 100%. The hierarchies
translate into DODS Structures and Sequences, which require the as-yet
not released DODS version 3.3 changes.

I hope this helps to get you started, at least  ... or to stimulate
discussion from someone who knows HDF in greater detail than I do.

    - steve

===========================

Yunyao Qu wrote:

> Hi, All,
>
>  Can Ferret  handle HDF file?
>  If it could,  we would like to use Ferret to process HDF file to
> produce other formats of data.
>
>  Thanks
>  Frank

--
Steve Hankin
NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115-0070
ph. (206) 526-6080 -- FAX (206) 526-6744




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