Dear Jim, David,
Sorry for dropping this thread from last August.
I agree that the convention does not have to adhere rigidly to the NUG definition of a coordinate variable, but the text of version 1.7 implies that it does. David's suggested rewording of the definition of an auxiliary coordinate below would begin to address this, but there may be other places where a change is needed. E.g.
The current text says that "The value of the coordinates attribute is a blank separated list of the names of auxiliary coordinate variables." (3rd paragraph in section 5) -- I think you are saying that this is not the meaning you want?
I'm still not entirely clear what you are trying to achieve here .. the definition of auxiliary coordinate in version 1.7 looked fine to me (where it is clearly stated in relation to the NUG definition of a coordinate variable): I'm not objecting to your change, but it might help this conversation if you explained the rationale behind the change.
regards,
Martin
________________________________
Martin,
The height scalar variable you are referring to is numeric, right? It
may not be a coordinate variable in the pure NUG sense, but CF isn't
bound by exact adherence to NUG if it defines its terms, and David has
posted the relevant sections from the Conventions. It is clear to me
that those sections declare that a numeric scalar variable may serve as
a valid 'true' coordinate variable, /as opposed to/ an auxiliary
coordinate variable. The mechanism for relating a scalar coordinate
variable to a data variable is through the 'coordinates' attribute, but
that does not force it to be considered to be an auxiliary coordinate.
Martin is trying to find a way to clarify these concepts, since you seem
to find them unclear.
What would make it clearer to you that CF declares that the height
scalar variable mentioned in this discussion qualifies as a true or full
or complete (or whatever word you prefer) coordinate and is not
relegated to auxiliary coordinate status?
Grace and peace,
Jim
On 7/31/17 10:10 AM, martin.juckes at stfc.ac.uk<
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata> wrote:
>
> Why?
>
> *From:*David Hassell [mailto:david.hassell at ncas.ac.uk<http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata>]
> *Sent:* 31 July 2017 14:50
> *To:* Juckes, Martin (STFC,RAL,RALSP)
> *Cc:* CF Metadata
> *Subject:* Re: [CF-metadata] Use of axis attribute in an auxillary
> coordinate
>
> Hi Martin,
>
> In #104 <https://cf-trac.llnl.gov/trac/ticket/104> perhaps we should
> have updated the definition of an auxiliary coordinate variable to
> reflect the clarification of scalar cooridnate variables. Something like:
>
>
> auxiliary coordinate variable
>
> Any netCDF variable that contains coordinate data, but is not a
> coordinate variable (in the sense of that term defined by the NUG and
> used by this standard - see below) */nor is functionally equivalent to
> one (such as a numeric scalar coordinate variable)/*. Unlike
> coordinate variables, there is no relationship between the name of an
> auxiliary coordinate variable and the name(s) of its dimension(s).
>
> This could be done with a defect ticket.
>
> All the best,
>
> Diavd
Received on Mon Feb 26 2018 - 10:16:29 GMT
