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Re: netCDF - ... and file size [message #15393]

Fri, 14 May 1999 00:00

bowman
Messages: 121
Registered: September 1991

Senior Member

In article <373C8FDA.3C47B2@io.harvard.edu>, Martin Schultz
<mgs@io.harvard.edu> wrote:

> Martin Schultz wrote:
>>
>
> ... the file size of my test netCDF file is practically identical to the
> size of my
> "primitive" binary file (all dat being stored as float). Wouldn't it be
> nice if netCDF would support compression? In my case that would mean a
> reduction by a factor of 4 (using gzip). Or would they loose
> cross-platform portability then?

There has been talk about doing this, but I think there are considerable
obstacles. You can maintain cross-platform compatibility by using 'scale'
and 'offset' attributes to linearly transform your variables and store
them as, for example, 2-byte INTs instead of 4-byte FLOATS (at some cost
in precision, of course).

Ken

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Re: netCDF - ... and file size [message #15396 is a reply to message #15393]

Fri, 14 May 1999 00:00

Martin Schultz
Messages: 515
Registered: August 1997

Senior Member

Martin Schultz wrote:
>

... the file size of my test netCDF file is practically identical to the
size of my
"primitive" binary file (all dat being stored as float). Wouldn't it be
nice if netCDF would support compression? In my case that would mean a
reduction by a factor of 4 (using gzip). Or would they loose
cross-platform portability then?

Martin.

--

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Martin Schultz, DEAS, Harvard University, 29 Oxford St., Pierce 109,
Cambridge, MA 02138 phone (617) 496 8318 fax (617) 495 4551
e-mail mgs@io.harvard.edu web http://www-as/people/staff/mgs/

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Re: netCDF - ... and file size [message #15464 is a reply to message #15393]

Mon, 17 May 1999 00:00

robert.m.candey.1[1] is currently offline

robert.m.candey.1[1]
Messages: 2
Registered: March 1999

Junior Member

In article <373C8FDA.3C47B2@io.harvard.edu>, Martin Schultz
<mgs@io.harvard.edu> wrote:

> Martin Schultz wrote:
>>
>
> ... the file size of my test netCDF file is practically identical to the
> size of my
> "primitive" binary file (all dat being stored as float). Wouldn't it be
> nice if netCDF would support compression? In my case that would mean a
> reduction by a factor of 4 (using gzip). Or would they loose
> cross-platform portability then?
>
> Martin.

The sister format (CDF) to netCDF does have compression
<http://nssdc.gsfc.nasa.gov/cdf/cdf_home.html>. We have a nice ingest
routine (read_myCDF.pro) at
<ftp://nssdc.gsfc.nasa.gov/pub/CDAWlib/source/> (whole library tarred up
at <ftp://nssdc.gsfc.nasa.gov/pub/CDAWlib/unix/>). See
<http://cdaweb.gsfc.nasa.gov/> fo plots using the library.

--
Robert.M.Candey@gsfc.nasa.gov 1-301-286-6707 (286-1771 fax)
NASA Goddard Space Flight Center, Code 632
Greenbelt MD 20771 USA <http://nssdc.gsfc.nasa.gov/personnel/rcandey/>

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