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On 7/26/2011 2:34 PM, Lynnes, Christopher S. (GSFC-6102) wrote:
Im not sure what the difference between the high and low gain, but it might be a good candidate to separate into 2 variables.On Jul 26, 2011, at 3:05 PM, John Caron wrote:On 7/26/2011 12:26 PM, Tom Rink wrote:Upendra, On 7/26/11 1:07 PM, Upendra Dadi wrote:Jim, Could you please clarify how to represent data which contain bands with multiple spatial resolutions using you scheme? I am thinking of MODIS data: http://en.wikipedia.org/wiki/Moderate-Resolution_Imaging_Spectroradiometer#MODIS_Bands As you can see, not all the bands have same spatial resolution (or spatial dimensions), even though all of them have same units. Could we even store all the bands in the same variable?I think multiple resolutions in same variable would be difficult and impracticable, the CF conventions for defining Projections, analytic or lat/lon, don't work like this. You'd probably have to define another dimension to index the different resolutions for the data, lon and lat variables. I would think this would be pretty messy. TomCorrect, you need seperate variables for different resolutions. However, theres no problem with having multiple coordinate systems in the same file. So if you chose, you would create multiple groups of variables, each group with their own coordinates.The HDF files for MODIS currently do separate the resolutions into different variables. However, MODIS presents some other issues, such as having both low-gain and high-gain versions of the same band in the same 3D variable. Currently, they handle this inside the file by calling one band "13" and another "13.5", but this is a bit opaque. I can never remember which is low and which is high.
if you accept that a data variable must have either a wavelength or wavenumber coordinate, then we need just those coordinate values (or bounds) to be unique, so they can be named uniquely by coordinate value. Other auxilary coordinates like bandwidth dont need to be unique.There are also two bands (21 and 22) with different band "numbers" but the same bandwidth (different Spectral Reflectance).
I have been mentally struggling to understand how these would fit in the various "band" dimension/coordinate proposals. Would it be useful to begin a set of examples for actual instruments so that the less CF-savvy amongst us could see the implications?
yes, very helpful.
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