[CF-metadata] Using add_offset & scale_factor with coordinate variables

Etienne Tourigny etourigny.dev at gmail.com
Tue Apr 10 13:11:30 MDT 2012


If netcdf-4 is an option for you, it might be simpler to compress
(deflate) the coordinate variables, this works transparently.

Etienne

On Tue, Apr 10, 2012 at 2:40 PM, David Hassell
<d.c.hassell at reading.ac.uk> wrote:
> Hello Randy,
>
> I, too, recently thought about this when working on some CF processing
> software (cf-python), but couldn't think of a use case so didn't
> pursue it - and now you have one!
>
> It seems to me that the use of scale_factor and add_offset is intended
> for (but not restricted to ...?) the reduction of dataset size
> (chapter 8). Is the requirement in your example for space saving, or
> some other convienience? I personally think that the latter case is
> better served by an appropiate setting of the units attribute (such as
> units="0.555555555555556 K @ 459.67" if we have converted from Kelvin
> to Fahrenheit).
>
> Anyway, I can't think of a reason not to allow these attributes on
> coordinates - these variables can be very large, after all.
>
> All the best,
>
> David
>
> ---- Original message from Randy Horne (01PM 05 Apr 12)
>
>> Date: Thu, 5 Apr 2012 13:05:45 -0400
>> From: Randy Horne <rhorne at excaliburlabs.com>
>> To: cf-metadata at cgd.ucar.edu
>> X-Mailer: <IMail v8.21>
>> Subject: [CF-metadata] Using add_offset & scale_factor with coordinate
>>  variables
>>
>> Folks:
>>
>> Appendix A, Table A.1 in the CF conventions state that add_offset and scale_factor can be used with data variables, but not coordinate variables.
>>
>> For the data producing system I am working (GOES-R Ground Segment) it is particularly convenient to make use of add_offset and scale_factor with our coordinate variables.
>>
>> Is there an issue with changing the conventions to allow this ?
>>
>> very respectfully,
>>
>> randy
>>
>>
>>
>>
>> ..............End of Message ...............................-->
>>
>>
>>
>>
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>
>
> --
> David Hassell
> National Centre for Atmospheric Science (NCAS)
> Department of Meteorology, University of Reading,
> Earley Gate, PO Box 243,
> Reading RG6 6BB, U.K.
>
> Tel   : 0118 3785613
> Fax   : 0118 3788316
> E-mail: d.c.hassell at reading.ac.uk
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