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 <[email protected]
<mailto:[email protected]>> 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
<[email protected] <mailto:[email protected]>>
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
[email protected] <mailto:[email protected]>
828-271-4900
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