Hi Jon -
I think the term 'resolution' might be more correct in this case than
'precision' - These are the definitions we use, although I can't quite
find the source:
* Resolution is the fineness to which an instrument can be read.
* Precision is the fineness to which an instrument can be read
repeatably and reliably.
I'm also using the attribute 'C_format' - don't recall exactly which
convention
uses that, but it's a good way to indicate 'vagueness' - but I'm not
sure how
or if it could be used to indicate that the dates are only good to whole
days.
Cheers - Nan
> Hi Mike,
>
> This is useful, thanks. However, I'm not sure that this concept of
> "uncertainty" is exactly the same as my notion of "nominal precision"
> (maybe I've chosen a bad name). For example, I know for sure that an
> OSTIA daily analysis field is considered representative of a certain
> day, but the specification of exactly how the field is representative is
> complex. This, to me, is not quite the same as saying that the field
> represents 12 noon on that day, plus or minus 12 hours. It's more
> "imprecision" than "uncertainty".
>
> Would you agree with this distinction?
>
> Cheers, Jon
>
> -----Original Message-----
> From: McCann, Mike [mailto:mccann at mbari.org]
> Sent: 03 June 2010 19:47
> To: Jon Blower; Steve Hankin
> Cc: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] bounds/precision for time axis
>
> Hi Jon,
>
> The OceanSITES data management team has recognized a desire to include
> an
> attribute named "uncertainty" for all of our in situ measurements that
> are
> in our netCDF files (that also follow the CF convention).
>
> We chose the attribute "uncertainty" after much discussion around terms
> such
> as "precision" and "accuracy" because we felt that "uncertainty"
> encompasses
> several aspects of metrology and is more usable and simple to understand
> for
> the consumers of the data.
>
> This attribute can also be extended to the coordinate variables, e.g. If
> the
> precision of my clock and upstream sampling techniques was 5 seconds I'd
> assign 5 to the .uncertainty attribute on my time coordinate.
>
> Would this approach work for your data?
>
> -Mike
>
>
>
>
--
*******************************************************
* Nan Galbraith (508) 289-2444 *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 *
*******************************************************
Received on Thu Jun 03 2010 - 14:23:11 BST
