[CF-metadata] scalar coordinate variables

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 12 Jun 2013 11:18:00 +0100

Dear Mark

I suppose it therefore makes sense for David and me to write an alternative
proposal, to insert some words in the convention document to make clearer what
we understand to be the intention of scalar coordinate variables. OK?

As you know, we think they are not a distinct concept in the data model, just a
convenient shorthand for storing coordinates of size one in the CF-netCDF file,
to avoid defining dimensions of size one. That's why they were introduced to
the convention, and I'm not convinced there is a need to change the
interpretation. I will draft some words to clarify that interpretation.

I now think the discrete sampling geometry is a more complicated case, where we
are using CF mechanisms to pack several data variables into one data variable,
in effect, using one of the four different representations according to the
situation. Therefore I think the interpretation in terms of the data model may
need to be different. I suggest we should stick to CF 1.5 until we have
resolved the question of scalar coordinates i.e. leave out the discrete
sampling geometries until we have our other ideas sorted out. The existing trac
tickets are about CF 1.5, as you know.

Best wishes

Jonathan

----- Forwarded message from "Hedley, Mark" <mark.hedley at metoffice.gov.uk> -----

> From: "Hedley, Mark" <mark.hedley at metoffice.gov.uk>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> Date: Wed, 12 Jun 2013 09:33:17 +0000
> Subject: [CF-metadata] scalar coordinate variables
>
>
> It's been suggested to me that it might help open up this discussion if I could post up a suggested text for scalar coordinate variables, which recognises their semantics within NetCDF files.
>
> If there is some feeling that this is a helpful step, I will raise a trac ticket to discuss the finer points of detail on wording and implications and look to possible approval by the community.
>
> These are suggested alterations to sections in the conventions text. I think all of the current examples (5.11, H4, H5 and H9) remain valid as they are. I think the conventions would benefit from further examples, I leave the discussion on which cases could be most useful to illustrate the usage and implications of scalar coordinates to a potential trac ticket.
>
> mark
Received on Wed Jun 12 2013 - 04:18:00 BST