Hi folks,
I wonder if there isn't a more generic pattern sitting behind these
proposals. On the assumption that people are likely to want to use
similar offsets for other coordinate variables - e.g. x_offset,
y_offset, z_offset, lat_offset, lon_offset, and so on - would there be
any merit in specifying the more general-purpose standard_name of
'coordinate_offset', which would then be used in association with a new
attribute called, say, 'base_coordinate' or 'ref_coordinate' (comparable
to Jonathan's proposed 'relative_to' attribute) which would define the
reference/datum coordinate variable?
Then, in CDL, we'd have something like...
variables:
double time(time) ;
:standard_name = "time" ;
...
double delta_t(time) ;
:standard_name = "coordinate_offset" ; # or just plain "offset" ?
:ref_coordinate = "time" ;
...
(In some cases, of course, the time coordinate might be a scalar
coordinate, in which case the dimensions of the above two variables
would be different).
Adopting an approach along these lines would seem to confer the
advantage of avoiding a proliferation of standard names of the form
'X_offset'. That said, however, there are probably some CF nuances that
I've not thought of :-)
Regards,
Phil
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of plieger
> Sent: 03 February 2011 09:14
> To: Jonathan Gregory
> Cc: CF metadata
> Subject: Re: [CF-metadata] MSG CPP standard name for
> time_offset_of_observation / pixel_delta_time
>
> Dear Jonathan,
>
> > Do you think the standard name alone is sufficient? Proposing a new
> > attribute is more work than proposing a standard_name,
> since it means
> > amending the CF standard. I can see there could be value in a
> > relative_to attribute, but it might be an unnecessary
> complexity. I wonder what you and others think.
>
> The standard name alone is sufficient for our case. I agree
> with you that we should not add unnecessary complexity to the
> CF standard. I think we will use the standard name 'time_offset'.
>
> Best regards,
> Maarten
>
>
>
> On 02/02/2011 05:15 PM, Jonathan Gregory wrote:
> > Dear Maarten
> >
> > What you write about pixeltime as an aux coord var (y,x) and your
> > ncdump look sensible to me. I think that's all fine.
> >
> >> The standard_name time_offset (s) seems good to me. In the
> long name
> >> we can add an explanation that this variable deals with the time
> >> offset for each pixel.
> >
> > OK. So that is a definite proposal for a new standard name.
> >
> > Do you think the standard name alone is sufficient? Proposing a new
> > attribute is more work than proposing a standard_name,
> since it means
> > amending the CF standard. I can see there could be value in a
> > relative_to attribute, but it might be an unnecessary
> complexity. I wonder what you and others think.
> >
> > Best wishes
> >
> > Jonathan
> >
>
>
> --
> Maarten Plieger
> KNMI, R&D Information and Observation Technology, De Bilt
> (t) +31 30 2206330
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