Before responding to Jim, can I propose this for the second sentence: "Missing
data are permitted in an auxiliary coordinate variable only at points where all
the referencing variables also have missing data." Trying to fix some nits and
make it a bit more parseable.
Jim, I'm not sure I understand your question. If you have data points for a
variable ('D') where you do not have data for the auxiliary coordinate variable
('A'), than you have to either (a) somehow derive the corresponding auxiliary
coordinate variable (A) data before creating the file, or (b) not specify the
intended auxiliary coordinate variable A as an auxiliary coordinate variable
for that data variable D. The intent being that it's only an auxiliary
coordinate variable if you have a datum for every referencing data point.
On the other hand, if you have _extra_ data in the auxiliary coordinate
variable A, but no corresponding data in the regular data variable D, all is
fine, it doesn't matter, no action is needed.
john
On Feb 26, 2014, at 07:30, Jim Biard <[email protected]> wrote:
> Hi.
>
> If my auxiliary coordinate is measured, as opposed to computed (in a
> trajectory or swath, for example), I may very well have a situation where I
> have measurements of data where I don’t have a measurement of location. If I
> wish to preserve the data measurements, I need to able to have fill in my
> auxiliary coordinate variables without fill in my data variables. How will I
> handle that given the proposed limitations?
>
> Grace and peace,
>
> Jim
>
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>
> On Feb 26, 2014, at 5:18 AM, Hedley, Mark <[email protected]>
> wrote:
>
>>> 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."
>>
>> I would support this, I think there are use cases where missing data at the
>> 'same location' in the data array and an auxiliary coordinate array is valid
>> and sensible.
>>
>> Rich's case is clearly valid. I have a couple more which I can illustrate
>> in further detail as we pursue this requirement.
>>
>> mark
>>
>> ________________________________________
>> From: CF-metadata [[email protected]] on behalf of Signell,
>> Richard [[email protected]]
>> Sent: 18 February 2014 21:01
>> To: Gregory, Jonathan
>> Cc: CF metadata
>> Subject: Re: [CF-metadata] How to handle a forecast model with non-monotonic
>> coordinate variables
>>
>> 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
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