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
> >
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Received on Thu Dec 21 2006 - 10:06:23 GMT
