I was unaware of this restriction on aux coordinate variables.
On 3/26/12 4:24 AM, Jonathan Gregory wrote:
Appendix A notes that missing data is allowed in aux coord vars only in the
case of discrete sampling geometries. This means the checker could regard it as
an error also if it finds any missing data in aux coord vars, unless a valid
featureType att is present, arising from 9.6, in addition to the above.
However, I think the convention should be clear that this is not allowed except
for discrete sampling geometries, so I'll open a defect ticket for that.
For something like towed CTD data, you might have a period of time where
data from the pressure sensor is missing. If neither the coordinate or aux
coordinate can contain null values, does this mean the only options are
interpolating Z or removing that section of data?
Sometimes, if the pressure can clearly be interpolated, we'd prefer to fill
the bad section with null Z values, and let the user decide if he would
like to
interpolate - otherwise the QC information can be lost when data is
extracted
from the file.
Cheers -
Nan
On 3/23/12 6:29 PM, John Caron wrote:
On 3/23/2012 1:59 PM, Jim Biard wrote:
Hi.
Jonathan's reply contained the section:
9.6 Where any auxiliary coordinate variable contains a missing
value, all
other coordinate, auxiliary coordinate and data values
corresponding to that
element should also contain missing values.
I thought I understood that missing values were forbidden for true
coordinate variables. Has this changed?
No, coordinate variable cant have missing values but auxiliary
coordinates can.
This requirement seems wrong to me anyway. If the values in the data
and auxiliary coordinate variables come from an external data source,
it is entirely possible that you could have a measurement missing
from one without it being missing from the other. Why force a
missing value into the data when you might, in fact, have a valid value?
An auxiliary coordinate is important to have for valid data, not some
optional information. If it is optional, dont make it an auxiliary
coordinate.
Allowing missing values in auxiliary coordinates is very useful, eg
see the discrete sampling proposal, allowing you to use a rectangular
array to store ragged arrays.
John
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