Dear Jim
Is it a trajectory feature using the discrete sampling geometry convention
of section 9? In that case it is required that there should be a nominal
longitude, latitude and time for each observation along the trajectory.
However you could also supply data variables of longitude and latitude with
cell_methods along the same trajectory, and these data variables could be
named by the coordinates attribute of other data variables (serving as
auxiliary coordinate variables), to provide a more precise indication of
location, as in section 9.5.
Yes, the cell_methods would be "cell methods where there are no coordinates"
of section 7.3.4 since you don't have longitude and latitude dimensions. It is
permitted to specify "area:" for a cell method even if there are no horizontal
dimensions specified.
Cheers
Jonathan
----- Forwarded message from Jim Biard <jbiard at cicsnc.org> -----
> Jonathan,
>
> What I mean is, this is not gridded data. The operations being performed (mean latitude, etc) are over a geographic region that is not described anywhere in the file, which is the region considered to be the extent of the weather system. So, you are saying that this trajectory case falls under the ?Cell methods when there are no coordinates? case, is that right?
>
> Jim
>
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> On Mar 4, 2014, at 9:30 AM, Jonathan Gregory <j.m.gregory at reading.ac.uk> wrote:
>
> > Dear Jim
> >
> >> Even though there are no cells? That?s the part that I?m feeling confused about.
> >
> > Sorry, I'm not sure why you say there are no cells. "Cell" does not imply any
> > number of spatial dimensions - is that the problem? It means the portion of
> > the domain, of whatever dimensionality, which is represented by a particular
> > data value. The cell_methods attribute indicates how that data value represents
> > unrecorded variability of the quantity represented within the cell.
> >
> > Best wishes
> >
> > Jonathan
> >
> >> On Mar 3, 2014, at 1:22 PM, Jonathan Gregory <j.m.gregory at reading.ac.uk> wrote:
> >>
> >>> Dear Jim
> >>>
> >>> Yes, I think such an approach is applicable. Any data variable can have
> >>> cell_methods and any data variable could be used as an aux coord variable.
> >>> Although unusual, I don't see a reason not to have data variables of latitude
> >>> and longitude, qualified by cell_methods, if required.
> >>>
> >>> Best wishes
> >>>
> >>> Jonathan
> >>>
> >>> ----- Forwarded message from Jim Biard <jbiard at cicsnc.org> -----
> >>>
> >>>> Subject: Re: [CF-metadata] can a cell method be an attribute of an auxiliary
> >>>> coordinate variable ?
> >>>> From: Jim Biard <jbiard at cicsnc.org>
> >>>> Date: Fri, 28 Feb 2014 14:01:24 -0500
> >>>> CC: cf-metadata at cgd.ucar.edu
> >>>> To: Jonathan Gregory <j.m.gregory at reading.ac.uk>
> >>>> X-Mailer: Apple Mail (2.1874)
> >>>>
> >>>> Jonathan,
> >>>>
> >>>> So, I?ve got a broader question. We have a case in hand with trajectory data for a physically extensive weather system. Two data variables are the mean longitude and latitude of the system, which we are treating as the auxiliary coordinate variables. Other data variables contain measurements such as maximum latitude at the mean longitude, etc. Are cell_methods applicable in this case? There is no grid, so the cell would be the area covered by the system, and the extents of this area are not described.
> >>> _______________________________________________
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> >>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> > _______________________________________________
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>
----- End forwarded message -----
Received on Tue Mar 04 2014 - 09:39:00 GMT
