[CF-metadata] bounds/precision for time axis

Jonathan Gregory j.m.gregory at reading.ac.uk
Fri Jun 4 01:43:20 MDT 2010


Dear Jon

> My worry is the subtle distinction between
> "resolution" and "bounds/cell_methods", which I would have to think
> through properly at some more sociable hour.

I think the distinction is:

* resolution of the time-bounds refers to how accurately you can characterise
the point at which, or the interval within which, the data was collected. E.g.
was it at 1200, or from midnight to midnight, with a precision of 1 ms, or of
1 h? Perhaps that could be recorded in CF by using ancillary_data and
standard_name modifiers (CF 3.3 and 3.4) for the coordinates or bounds. (I'm
not exactly sure how, since they were designed for data variables.)

* cell_methods refers to how the value in the data variable represents the
variation within the cell - is it a single value at a particular point (point),
or a single value selected somehow from all the values within the interval
(maximum, minimum, median), or a combination of values (mean, standard_
deviation)? I suggested "cell" could be used to indicate, for an intensive
variable, that it is an ill-defined combination of values which is somehow
typical of the cell. We don't have to use "cell", which I suggested just
because it already exists. We could use something else e.g. "typical" or
"representative".

Best wishes

Jonathan



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