Jonathan,
In the very last comment in ticket #85
(
https://cf-pcmdi.llnl.gov/trac/ticket/85) you say:
"In the "Description" column of Appendix A, in the entries for
_FillValue andmissing_value, replace "Not allowed for coordinate data
except in the case of auxiliary coordinate varibles in discrete
sampling geometries." with "Allowed for auxiliary coordinate variables
but not allowed for coordinate variables."
This would seem to allow missing values in auxilliary coordinates for
grid datatypes, which is what we need for the use case I presented.
We could modify this to:
"Allowed for auxiliary coordinate variables but not allowed for
coordinate variables. Missing data is only permitted in auxiliary
coordinate varirables only at points where the data variable(s)
concerned has missing data."
Thanks,
Rich
On Tue, Feb 18, 2014 at 1:08 PM, Jonathan Gregory
<j.m.gregory at reading.ac.uk> wrote:
> Dear Jim
>
>> As far as I have ever been able to tell from CF (pre 1.6), there has never been a proscription of missing values in auxiliary coordinates. True coordinate variables (as I think of them) contain definitions of independent axes, which are not acquired data. As a result, it makes no sense for them to have missing values. Auxiliary coordinate variables may very well contain acquired data values, and properly able to have elements marked as missing, independent of whether or not other variables are missing values for the corresponding elements.
>
> _FillValue and missing_value are allowed by Appendix A only for data variables
> (D) not coordinate variables (C) in version 1.5 and earlier. In version 1.6
> this was clarified and ticket 85 clarifies it further, for version 1.7.
>
> We allow missing data in discrete sampling geometries for elements which don't
> correspond to any location i.e. they're just not used at all.
>
> Best wishes
>
> Jonathan
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--
Dr. Richard P. Signell (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598
Received on Tue Feb 18 2014 - 14:01:21 GMT
