Thanks Bryan - but surely a viz tool should highlight over/undershoots
to prompt the user to choose a better scale? E.g. we colour
over/undershoots in black to show "data out of colour range". Maybe
not all tools do this (in fact I know they don't - I've seen some that
colour out-of-range values in the same colour as the min/max values,
which seems odd to me).
But yes, the actual min-max would be very useful indeed - it would
then be easy to get the min-max for a collection of data files too.
Is there a standard CF attribute for this?
Thanks also Roy for sharing what you do in BODC - very helpful.
Merry Christmas and Happy New Year all!
Jon
On 12/21/06, Bryan Lawrence <b.n.lawrence at rl.ac.uk> wrote:
>
> Steve is so right!
>
> The ozone hole was ignored for years because someone decided to omit
> non-sensible values: the problem is that the folk who choose "sensible"
> don't choose the colour scale at the viz end ... so you can't rely on
> undershoots and overshoots being obvious to the end-user at first
> parse... here be dragons!
>
> A safe alternative which might save time in visualising large datasets
> would be for the *actual* minimum and maximum to be optionally stored as
> attributes somehow ... this would be very useful for data mining as well
> as visualisation ...
>
> Bryan
>
> On Thu, 2006-12-21 at 09:39 -0700, Steve Emmerson wrote:
> > 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
> > >
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://www.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
--
--------------------------------------------------------------
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 - 12:12:30 GMT
