Hi Ag (and list),
I guess there could be a dual approach - each standard name has a
"default" sensible range, but an individual file could override this -
for example a file that contains temperature data only for the Arctic
Ocean would probably define a narrower data value range for display.
Cheers, Jon
On 12/21/06, Stephens, A (Ag) <A.Stephens at rl.ac.uk> wrote:
> Dear all,
>
> I think these attributes would be more appropriately dealt with in the definition of the quantity - i.e. held with the standard_name or other fixed vocabulary metadata. It is very unlikely to change quickly and can therefore be considered as fixed, in which case it would not be needed in every NetCDF file containing that variable. However, perhaps this approach is less workable than something you can put in the NetCDF variable metadata.
>
> Cheers,
>
> Ag
>
>
> -----Original Message-----
> From: cf-metadata-bounces at cgd.ucar.edu on behalf of Roy Lowry
> Sent: Thu 21/12/2006 9:48 AM
> To: cf-metadata at cgd.ucar.edu; jdb at mail.nerc-essc.ac.uk
> Subject: Re: [CF-metadata] attributes for min/max data values for visualization
>
> Dear All,
>
> I'm not sure how this would work because the valid range could be a function of both the Standard Name and the Cell Method.
>
> Cheers, Roy.
>
> >>> "Jon Blower" <jdb at mail.nerc-essc.ac.uk> 12/21/2006 9:35 am >>>
> 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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--
--------------------------------------------------------------
Dr Jon Blower Tel: +44 118 378 5213 (direct line)
Technical Director Tel: +44 118 378 8741 (ESSC)
Reading e-Science Centre Fax: +44 118 378 6413
ESSC Email: jdb at mail.nerc-essc.ac.uk
University of Reading
3 Earley Gate
Reading RG6 6AL, UK
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Received on Thu Dec 21 2006 - 04:17:26 GMT
