My preference is that one explicitly puts in the units. For dimensionless,
"1" or "" is ok for udunits. If the units attribute isnt there, I assume
that the user forgot to specify it, so the units are unknown.
Im not sure what CF actually says, but it would be good to clarify.
John
On Thu, Oct 30, 2014 at 2:37 AM, Hedley, Mark <mark.hedley at metoffice.gov.uk>
wrote:
> Hello CF
>
> > From: CF-metadata [cf-metadata-bounces at cgd.ucar.edu] on behalf of
> Jonathan Gregory [j.m.gregory at reading.ac.uk]
>
> > Yes, there are some standard names which imply string values, as Karl
> says. If the standard_name table says 1, that means the quantity is
> dimensionless, so it's also fine to omit the units, as Jim says.
>
> I would like to raise question about this statement. Omitting the units
> and stating that the units are '1' are two very different things;
> dimensionless != no_unit
> is an important statement which should be clear to data consumers and
> producers.
>
> If the standard name table defines a canonical unit for a standard_name of
> '1' then I expect this quantity to be dimensionless, with a unit of '1' or
> some multiple there of.
> If the standard name states that the canonical unit for a standard_name is
> '' then I expect that quantity to have no unit stated.
> Any deviation from this behaviour is a break with the conventions. I have
> code which explicitly checks this for data sets.
>
> Are people aware of examples of the pattern of use described by Jonathan,
> such as a categorical quantities identified by a standard_name with a
> canonical unit of '1'?
>
> thank you
> mark
>
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