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

From: Randy Horne <rhorne>
Date: Wed, 11 Apr 2012 10:50:54 -0400

The allure of using add_offset & scale_factor with coordinate variables goes beyond saving space. For example, in our use case ?

(1)
Makes the s/w producing the product simpler.

(2)
The scale_factor also tells you what the horizontal spatial resolution is in a representation that aligns with the coordinate space.


very respectfully,

randy



On Apr 10, 2012, at 3:11 PM, Etienne Tourigny wrote:

> 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 _at_ 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 ...............................-->
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> CF-metadata mailing list
>>> CF-metadata at cgd.ucar.edu
>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>
>>
>> --
>> 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
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>


____________________________________

Randy C. Horne (rhorne at excaliburlabs.com)
Principal Engineer, Excalibur Laboratories Inc.
voice & fax: (321) 952.5100
url: http://www.excaliburlabs.com
Received on Wed Apr 11 2012 - 08:50:54 BST

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