Hi All,
I don't believe there was ever an intention to disallow missing values from
auxiliary coordinate variables. First, note that the definition of an
auxiliary coordinate variable in section 1.2 makes no mention of this while
it is explicit in the definition of a coordinate variable that missing
values are not allowed. Furthermore, note that in section 5.3 the
discussion of the reduced horizontal grid contains the statement "Storing
this type of gridded data in two-dimensional arrays wastes space, and
results in the presence of missing values in the 2D coordinate variables."
The current feedback from the community argues that allowing missing values
in the auxiliary coordinate variables is a useful feature. Even if we'd
made the wrong choice initially it would be time to revisit the point. But
we didn't :)
Brian
On Tue, Mar 27, 2012 at 07:21:38AM -0400, Rich Signell wrote:
> Folks,
> There certainly are a fair number of "grid" featureTypes that also
> would benefit from FillValues being allowed on aux coordinate
> variables.
>
> Consider this NOAA coastal ocean model grid for Chesapeake Bay:
> http://screencast.com/t/Humzu7F69
> and a zoom in on one of the tributaries:
> http://screencast.com/t/eMLBhHEHO1
>
> Although the lon,lat and bathymetry values shown here can be
> represented by 2D arrays with fillValues, it's impossible to fill in
> the missing values with any kind of smooth function. Each tributary
> is being mapped from computational space to coordinate space using
> separate conformal transformations.
>
> This is a fairly common case, and it would be too bad to exclude it
> from being described with CF conventions.
>
> -Rich
>
> On Mon, Mar 26, 2012 at 2:09 PM, Randy Horne <rhorne at excaliburlabs.com> wrote:
> > Jonathan:
> >
> > We are putting in fill values for these off-earth points in the data variables.
> >
> >
> > very respectfully,
> >
> > randy
> >
> >
> > Randy C. Horne (rhorne at excaliburlabs.com)
> > Principal Engineer, Excalibur Laboratories Inc.
> > voice & fax: (321) 952-5100
> > url: http://www.excaliburlabs.com
> >
> > PGP Public Keys available at:
> > A HREF="http://pgpkeys.mit.edu:11371">MIT's Key Server</A>
> >
> > ---------- Original Message ----------------------------------
> > From: Jonathan Gregory <j.m.gregory at reading.ac.uk>
> > Date: ?Mon, 26 Mar 2012 18:35:19 +0100
> >
> >>Dear all
> >>
> >>Regarding Randy's reply:
> >>
> >>> In the case of GOES-R (and also Meteosat) our coordinate variable values are N/S elevation angle and E/W scanning angle, which can be syntactically valid values albeit off the disk of the earth.
> >>
> >>In this case, are there data values, or is the data missing at non-existent
> >>points?
> >>
> >>Regarding Nan's point, I would say that we do want CF to be inclusive. It
> >>would be a mistake to impose irrelevant requirements that deterred people
> >>from using the convention. In the case you mention, the chapter 9 convention
> >>for profiles wouldn't allow you to have missing data in Z; it permits missing
> >>data in coordinates only where the data is also missing.
> >>
> >>I suppose that the pressure information is actually data in the raw obs
> >>dataset. It would be legal to keep it in the file but not identify it as an
> >>auxiliary coordinate variable (in the coordinates attribute). Then it would
> >>be fine to having missing data in it. Would that be significantly less
> >>convenient? Just a thought.
> >>
> >>Cheers
> >>
> >>Jonathan
> >>_______________________________________________
> >>CF-metadata mailing list
> >>CF-metadata at cgd.ucar.edu
> >>http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> >>
> >
> >
> >
> > ..............End of Message ...............................-->
> >
> >
> >
> >
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>
>
>
> --
> Dr. Richard P. Signell?? (508) 457-2229
> USGS, 384 Woods Hole Rd.
> Woods Hole, MA 02543-1598
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Received on Tue Mar 27 2012 - 08:34:35 BST
