Steve,
I agree with you 100% about flagging data with quality flags, and I
wasn't suggesting that we throw anything away. I just was wondering
whether the title "CF-compliant" might be withheld from dataseta until
missing coordinates were supplied.
-Rich
On Thu, Mar 29, 2012 at 1:50 PM, Steve Hankin <steven.c.hankin at noaa.gov> wrote:
>
>
> On 3/29/2012 10:11 AM, Rich Signell wrote:
>
> Folks,
>
> I'm confused now. Are we proposing that we could have CF-compliant
> files that have no valid coordinate data, with the justification that
> somebody may figure the coordinates out later?
>
>
> Hi Rich,
>
> I'm afraid that this is the tip of an iceberg as we begin to try to
> acknowledge the differing viewpoints of observations versus models and
> products.? It would clearly be wrong to say to an observation program that
> it cannot include temperature and salinity measurements in their CF files,
> because the pressure sensor failed at that point.? While the resulting
> observations have greatly diminished value (and maybe ultimately prove to
> have no value at all), it would be wrong to throw the measurements away.
> This is in the same spirit that it is preferable to flag QC evaluations of
> "bad data" rather than throw them away.
>
> Should CF approach this head-on?? For example, CF could stipulate that IFF a
> data provider wants to include valid observations at points where auxiliary
> coordinates are missing, they must also include some kind of flag variable
> as well.? To me this seems unnecessary.? It is sufficient simply to state
> that under some circumstances there may be valid values at indices where
> auxiliary coordinates contain missing values -- perhaps adding that the
> circumstances will be rare and application-specific.
>
> Crystal ball:? Meeting the sometimes-conflicting needs of observations and
> models/products is going to lead to more of these discussions.
>
> ??? - Steve
>
>
>
> -Rich
>
> On Thu, Mar 29, 2012 at 1:01 PM, Steve Hankin <steven.c.hankin at noaa.gov>
> wrote:
>
> Returning to Nan's valid example, the proposed wording isn't very attuned to
> the valid needs of (in situ) observations.? If the pressure sensor fails,
> while other sensors remain active, then the Z auxiliary coordinate becomes
> unknown but other parameters remain valid.??? The observations have
> potential value (though greatly degraded, of course), because a future
> investigator may figure out how to estimate the Z position from other
> information.? For the investigator writing those applications, the
> statements below are wrong or misleading.
>
> I think the right thing to say is something along the lines of
>
> "Application writers should be aware that under some (rare) circumstances
> data auxiliary coordinate values may be missing, while other parameters at
> the corresponding indices remain valid.?? While special purpose applications
> may be able to glean useful information at these indices, most applications
> will want to regard data as missing where the auxiliary coordinates are
> missing "
>
>
> On 3/29/2012 9:05 AM, Jim Biard wrote:
>
> All,
>
> For the work I am doing right now, I am required to?not?fill in missing
> values in any variable. ?I encourage everyone to go with John Caron's idea.
>
> Grace and peace,
>
> Jim
>
>
> On Thu, Mar 29, 2012 at 12:01 PM, John Caron <caron at unidata.ucar.edu> wrote:
>
> To answer this concern, I would agree to modify the statement
>
> "Applications are free to assume that data is missing where the auxiliary
> coordinates are missing"
>
> to
>
>
> "Applications should treat the data as missing where the auxiliary
> coordinates are missing"
>
> My concern is that we shouldnt make a file "non CF compliant" just because
> the data provider would like to store data values where there arent
> coordinate values. But telling them that standard software _will_ ignore
> them seems good.
>
>
>
>
> On 3/29/2012 9:47 AM, Rich Signell wrote:
>
> Jonathan,
>
> +1 on ?your idea of only identifying variables as aux coordinate
> variables once they have valid values at valid data locations.
>
> -Rich
>
> On Thu, Mar 29, 2012 at 11:32 AM, Jonathan Gregory
> <j.m.gregory at reading.ac.uk> ?wrote:
>
> Dear Jim
>
> We are discussing auxiliary coordinate variables. They do not have to be
> 1D or monotonic. Those requirements apply to coordinate variables in the
> Unidata sense. CF distinguishes these two concepts in Sect 1.2.
>
> The point is, the information in the variable *is* coordinate
> information,
>
> I would say, if it's missing, it's not information.
>
> What if we say something along the lines of, "Applications should treat
> the
> data as missing where the auxiliary coordinates are missing when
> plotting
> data."? ?Would that resolve the problem?
>
> Plotting is not the only thing that an application might wish to use it
> for.
> If we said, more generally, "Applications should treat the data as
> missing for
> all purposes where the aux coord variables are missing", it would be
> almost
> the same as not allowing missing data in aux coord vars, since there
> would be
> no point in providing a data value if it was not permitted to use it.
>
> Although I am arguing one side, I could be convinced either way. But it
> does
> feel unsafe to me at present.
>
> Cheers
>
> Jonathan
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>
>
> --
> Jim Biard
> Research Scholar
> Cooperative Institute for Climate and Satellites
> Remote Sensing and Applications Division
> National Climatic Data Center
> 151 Patton Ave, Asheville, NC 28801-5001
>
> jim.biard at noaa.gov
> 828-271-4900
>
>
>
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>
--
Dr. Richard P. Signell?? (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598
Received on Thu Mar 29 2012 - 12:38:09 BST
