Dear All,
Thought it might be worth sharing what we do in BODC. The netCDF data files carry the minimum and maximum values (excluding values QC-flagged as bad) for each channel as attributes, which are automatically checked against 'sensible ranges' from our parameter dictionary (equivalent of Standard Names plus Cell Methods), with mandatory resolution of check fails either by further data flagging or relaxation of the dictionary limits. Seems to work pretty well.
I would see no harm in carrying both types of range as optional attributes. It's useful information that would be helpful to have labelled in a standardised manner.
Cheers, Roy.
>>> Steve Emmerson <steve at unidata.ucar.edu> 12/21/2006 4:39 pm >>>
Be careful. I've seen lots of sea surface temperatures of 38 celsius
and higher in my work as a research associate at the University of Miami.
Jon Blower wrote:
> Dear all,
>
> As some of you know, we at Reading have developed an online,
> interactive visualization tool for CF-compliant NetCDF data
> (http://lovejoy.nerc-essc.ac.uk:8080/ncWMS/godiva2.html). In order to
> create images of the data that are stored in the NetCDF files, the
> tool needs to know a sensible range of possible data values. For
> example, for sea temperature a sensible range is -5 to 35 C.
>
> Many data files specify the valid_min and valid_max attributes: these
> define the range of all possible values - outside this range, data are
> interpreted as missing values and are thus "hard" boundaries. This
> range is often set very wide to ensure that no true data values are
> interpreted as missing.
>
> I think it would be useful if there were a similar pair of attributes
> (say "suggested_min" and "suggested_max") that are interpreted by
> visualization tools as clues to generating a sensible colour scale,
> but values outside this range are not interpreted as missing.
>
> Do others think this is sensible, and is there anything similar existing
> in CF?
>
> Thanks,
> Jon
>
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Received on Thu Dec 21 2006 - 09:57:35 GMT
