Re: [cf-satellite] Proposal for band dimension and coordinate variable

On 7/26/2011 1:18 PM, Jim Biard wrote:
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

Hi Jim:

I am thinking that this is sufficient:

   float image(bandit=4, lines=5000, samples=5000);
     :coordinates = "polarization wavelength bandwidth";
     :units = "W m-2";
     :long_name = "the image";
     :standard_name = "the_image";

   float wavelength(bandit=4);
     :coordinates = "bandit";
     :units = "um";
     :long_name = "center wavelength";
     :standard_name = "radiation_center_wavelength";

   float bandwidth(bandit=4);
     :coordinates = "bandit";
     :units = "um";
     :long_name = "bandwidth";
     :standard_name = "radiation_bandwidth";

   short polarization(bandit=4);
     :coordinates = "bandit";
     :units = "radians";
     :long_name = "polarization";
     :standard_name = "radiation_polarization";

and then the convention would say something like:

"all data variables must have a wavelength (indicated by standard_name "radiation_center_wavelength") or a wavenumber (indicated by standard_name "radiation_center_wavenumber") coordinate."

it seems to me to suffice - an application looks for a coordinate with one of those 2 standard names, and now understands that this conforms to cf_satellite conventions, and knows what the dimension "band" is.





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