I use a singleton variable to record the magnetic correction that's been
applied to my wind and/or current variables; it's dim(1) and is listed as
an ancillary to any variables that have been affected by the rotation.
It could be an attribute of each of those variables, but making it a
free-standing
variable lets me give it units and attributes. That's important because I
record the model name and version date, the URL of the NGDC calculator
site,
the inputs to the model (date and location for which the calculation was
done)
and the estimated rate of change.
Maybe this is just a technicality - but I also use an empty 'container'
variable for
instruments, which has ancillary variables with a depth dimension for
manufacturer,
model, serial number, and reference URL. The instrument variable is
tied to 'obs data'
variables via NODC's 'instrument' attribute, but has no dimensions of
its own; the
individual component variables (like serial number) have a dimension
that matches
the depth dimension of the obs data variables.
- Nan
On 2/13/13 12:15 PM, Hedley, Mark wrote:
Hello CF community
I have been perusing the CF conventions again, particularly the section on
Ancillary Data
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch03s04.html
The conventions make the statement:
The nature of the relationship between variables associated via
ancillary_variables must be determined by other attributes.
The example given provides data variables which reference the same dimensions
in the file: thus they data arrays are the same size. However, the conventions
do not seem to mandate this.
I am interested in the use of the
ancillary_variables
attribute in real world datasets.
Do people have examples they can share of ancillary datasets which:
a. reference the same file dimensions as the data variable with the
ancillary_variables attribute references
b. reference a subset of the file dimensions referenced by the data variable
with the ancillary_variables attribute
c. reference file dimensions which are not referenced by the data variable
with the ancillary_variables attribute
I am particularly interested in examples of case c, as I feel this is markedly
different from cases a and b and requires a different kind of support if it is
in use.
many thanks
mark
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