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John,As we are feeling our way along here, I think we felt that we needed to have a single coordinate variable that we could hang attributes on that would make it clear that the associated dimension was enumerating different bands. Thus the "bandit" coordinate variable in my example that had an axis type of "index" and a standard_name of "band". If we dropped this coordinate variable altogether, the netCDF would still be proper, but where/how would we make it clear (to a general-purpose, CF-aware application) what the "bandit" dimension is for?
I guess a valid question to ask is - do we need such an indicator? Or put another way, what would be a good (or, the best) way to provide signposts for an application that is trying to recognize the type of data and do something smart with it? I am sure I don't know.
Grace and peace, Jim On 7/26/2011 2:51 PM, John Caron wrote:
On 7/25/2011 1:00 PM, Tom Whittaker wrote:Im not sure what the point of an "index coordinate" where coord(i) = i. is it just to have a container variable for where the other coordinates are referenced?John:On Mon, Jul 25, 2011 at 9:51 AM, John Caron<caron@xxxxxxxxxxxxxxxx> wrote:Another way to say the same thing: A coordinate variable must have values that are a "sampling" along a continuous domain. One sees this violated in the poorly designed AWIPS netcdf files, eg where all "temperature" values are crammed into one variable, and the coordinate values have both pressureand height and potential temperature, etc.Is it possible (practical) to define a simple "index" as a coordinate variable? What I'm thinking here is that we could define some coordinate axis types like "wavelength", etc., but would also need something that is just a simple index with a well-known attribute that could be easily recognized. In this "simple index" case, the data provider would have to supply other variables, dimensioned by "band" (for example) that would further describe the meaning of these indecies (for example: wavelength(band) would contain the central wavelength value). If this reasonable, then I could see us creating a few new coordinate axis names ("wavelength", "wavenumber") along with this simple index (name to be determined), and then start defining some standard_names for the ancillary metadata as well. tom_______________________________________________ cf-satellite mailing list cf-satellite@xxxxxxxxxxxxxxxxFor list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
-- Jim Biard Government Contractor, STG Inc. Remote Sensing and Applications Division (RSAD) National Climatic Data Center 151 Patton Ave. Asheville, NC 28801-5001 jim.biard@xxxxxxxx 828-271-4900
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