I seem to be doing better than most people for the compression ratio.
However Russ tried bzip2 and saw compression ratios of about 7:1, still
better than gzip. My data is not full of missing values but the fields are
relatively smooth (or most of them are). To be quite frank I'm not
entirely sure why it does quite so well!
Glenn
At 11:20 pm +0100 7/8/00, John Caron wrote:
>this is very impressive; i wonder if this file happens to have a lot of
>zeroes or missing data or something?
>
>floating point is known to be difficult to compress due to the fact the
>low order bits are essentially random.
>
>Russ Rew wrote:
>>
>> [Glenn Carver sent the appended note for the netcdfgroup mailing list.]
>>
>> I thought I would write highlighting the excellent compression of netcdf
>> files offered by the new compression tool 'bzip2'. bzip2 is a high quality
>> data compressor which is freely available. The website is :
>> "http://sourceware.cygnus.com/bzip2/";
>>
>> As an example with some of my netcdf files 200Mb uncompressed, bzip2
>> squashes these down to 20Mb whereas gzip can only manage 160Mb (both on
>> default settings).
>>
>> I hope this is of use to people on the netcdf mailing list.
>>
>> Glenn
>>
>> --
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Dr. Glenn Carver, Science Coordinator,
>> Centre for Atmospheric Science, Cambridge University, Chemistry Dept.,
>> Lensfield Road, Cambridge, CB2 1EW, UK.
>> mailto:Glenn.Carver@xxxxxxxxxxxxxxxx Phone: +44 (1223) 336524
>> http://www.atm.ch.cam.ac.uk/~glenn/ Fax: +44 (1223) 336473
>>
>> "I never think of the future, it comes soon enough"
>> - Albert Einstein
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
Dr. Glenn Carver, Senior Research Associate,
Centre for Atmospheric Science, Chemistry Dept., Cambridge University, UK
mailto:Glenn.Carver@xxxxxxxxxxxxxxxx http://www.atm.ch.cam.ac.uk/~glenn/
"I never think of the future, it comes soon enough"
- Albert Einstein
