[ESIP-CF] recording magnetic correction

[Nan Galbraith]

Hi all -

I'm looking for a somewhat standard way to encode the magnetic
correction that has been applied - or should be applied - to in situ
ocean currents and winds. I've been waiting for someone to pronounce
on this, as part of a larger scheme of providing provenance information
in NetCDF files, but if it's happened,  I've missed it.

This has got to be the most frequently asked question we get, though,
if we leave this information out of our CF (OceanSITES) files, or if we
provide it but are not specific enough.  So, while waiting for the right 
way
to do this, I've just been using a variable attribute:

    UWND:standard_name = "eastward_wind" ;
    UWND:magnetic_correction_applied = -17.233 ;

or, for some (raw, real-time) data sets,

    UWND:magnetic_correction_to_be_applied = -17.233 ;

I'd really like to provide  more information, though, so I'm thinking of
using an ancillary variable:

    UWND:standard_name = "eastward_wind" ;
    UWND:ancillary_variables = "MAGVAR" ;

    MAGVAR:long_name = "Magnetic correction applied" ;
    MAGVAR:units = "degrees_east" ;
    MAGVAR:source = "NOAA: National Geophysical Data Center (NGDC)" ;
    MAGVAR:reference_URL =
    "http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp" ;

    MAGVAR = -17.233 ;


Is there a better way - more standard - to include this information
in a NetCDF file? Will the CF Cluster address this type of question,
or is it too much of a detail?

Thanks -
Nan

-- 
*******************************************************
* Nan Galbraith        Information Systems Specailist *
* Upper Ocean Processes Group            Mail Stop 29 *
* Woods Hole Oceanographic Institution                *
* Woods Hole, MA 02543                 (508) 289-2444 *
*******************************************************



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