Jonathan:
With the growing interest in the CF conventions around the world by the
satellite CF data producer and user communities coupled with the ubiquitous
nature of wavelength-based satellite CF data sets, does it make sense to
add a paragraph to Section 4 Coordinate Types to discuss Spectral
Coordinates ?
very respectfully,
randy
++++
Dear Aleksandar > I know this will likely end up as a trac ticket but
would like first > to gauge the community's opinion about defining a new
coordinate type. > Satellite data originates as measurements at a number of
intervals of > the electromagnetic spectrum. These intervals are commonly
referred to > as bands or channels. Deciding on how to store the band
information is > one of the key issues toward a standardized representation
for > satellite data. > > The convention seems to allow storing of band
information either as a > numerical coordinate variable or as a string
auxiliary coordinate > variable. Yes, the CF standard could handle both of
those, without any modification. A trac ticket may not be needed. I
certainly think there is no problem at all for a numerical coordinate of
band wavelength. You need only to propose a new standard name for it, if
one is needed. There is already a generic standard name of
radiation_wavelength, included for use as a coord variable just as in your
first example. If you need something more specific, I would suggest
sensor_radiation_wavelength. The coord values for this would be the central
wavelengths, and you could also supply bounds specifying the range of
wavelengths covered by the sensor. Although string-valued auxiliary
coordinate variables are possible already, as used in your second example,
I would argue they are less useful as metadata than numerical ranges. That
is because the main use of CF is to support intercomparison of datasets,
which is better-defined if numbers are used. If there are widely used
definitions of named wavelength bands, required for intercomparison of many
datasets, a standard_name could be defined with a number of permitted
string values. I think this extension could probably be seen as a new
standard_name, not requiring a change to the conventions, although it could
be explicitly mentioned in section 6 like Roy is proposing for biological
taxa. Best wishes Jonathan
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Received on Wed Apr 10 2013 - 07:20:22 BST
