[CF-metadata] standard names for variables in raw?engineering units

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 13 Apr 2009 08:40:53 +0100

Dear Roy

The space is deliberate. The standard_name attribute consists of a standard
name followed optionally by a modifier. We introduced this syntax to allow us
to define ancillary data of various sorts e.g. a quality flag or a standard
error, without requiring a new set of standard names. See CF standard section
3.3. Perhaps we should have put it in a different attribute; this decision was
made years ago and I can't remember the discussion.

I made the raw_data suggestion thinking that, in the case where you have a
geophysical quantity, and you also want to save the raw data (perhaps that is
the case Nan describes), the raw data could be regarded as ancillary
information (a bit like a standard error). This mechanism, with a standard
name modifier and perhaps using ancillary_variables to point to it (CF 3.4),
might be suitable then. The modifier implies the units of the standard name
have been transformed in a certain way. We could therefore specify them to be
dimensionless for raw data, as that is a special case of transformation i.e.
replace units u with 1. They could be in the same units as the geophysical
quantity; that would need a different standard name modifier, which might be
appropriate for uncalibrated data. However they could not be in different
units, not related to those of the geophysical quantity.

This suggestion doesn't give enough information for the data to be processed.
It's just a way of labelling raw data as such.

If you want to identify the raw data as being a specific output from a
particular kind of instrument, I think it's much better to give a standard name
that indicates precisely what it is i.e. more specific than "rain gauge
raw data". Then the user could work out how to process it.

Cheers

Jonathan
Received on Mon Apr 13 2009 - 01:40:53 BST