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Aleksander: This has come up before on CF-satellite. checkout: http://www.unidata.ucar.edu/mailing_lists/archives/cf-satellite/2011/msg00025.html very respectfully, randy ---------------------------------------- From: "Aleksandar Jelenak - NOAA Affiliate" <aleksandar.jelenak@xxxxxxxx> Sent: Thursday, April 04, 2013 3:09 PM To: "cf-metadata@xxxxxxxxxxxx" <cf-metadata@xxxxxxxxxxxx> Subject: [CF-metadata] New CoordinateType: Spectral? Dear All, 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. When I open such a file in Unidata's ToolsUI software (the CoordSys tab) and select Parse Info, this is reported: <userAdvice>Coordinate Axis band does not have an assigned AxisType</userAdvice> Following this advice I have two questions: 1) What would be the benefits of having a coordinate type for describing satellite bands? Let's call this new type "spectral" for now. 2) Can the same coordinate type be assigned to both numerical and string variables? Such variables will not appear in the same file. String band information will cover cases where purely numerical band information is not sufficient to describe different bands, like for passive microwave instruments. I have included two examples in the P.S. section below to illustrate the concept. -Aleksandar P.S. Variant #1: Band information as a numerical coordinate variable dimensions: along_track = <integer> ; across_track = <integer> ; band = <integer> ; variables: short along_track(along_track) ; along_track:axis = "Y" ; short across_track(across_track) ; across_track:axis = "X" ; float band(band) ; band:standard_name = "sensor_band_central_wavelength" ; // proposed standard name in Nov 2012 band:units = "um" ; float lat(along_track, across_track) ; lat:standard_name = "latitude" ; lat:units = "degrees_north" ; float lon(along_track, across_track) ; lon:standard_name = "longitude" ; lon:units = "degrees_east" ; double time(along_track) ; time:standard_name = "time" ; time:units = "<units> since <datetime string>" ; time:calendar = "gregorian" ; float swath_band_data(along_track, across_track, band) ; swath_band_data:coordinates = "lon lat time band" ; Variant #2: Band information as a string auxiliary coordinate variable dimensions: along_track = <integer> ; across_track = <integer> ; band_enum = <integer> ; band_strlen = <integer> ; variables: short along_track(along_track) ; along_track:axis = "Y" ; short across_track(across_track) ; across_track:axis = "X" ; char band(band_enum, band_strlen) ; band:standard_name = "sensor_band_identifier" ; // proposed standard name in Nov 2012 float lat(along_track, across_track) ; lat:standard_name = "latitude" ; lat:units = "degrees_north" ; float lon(along_track, across_track) ; lon:standard_name = "longitude" ; lon:units = "degrees_east" ; double time(along_track) ; time:standard_name = "time" ; time:units = "<units> since <epoch>" ; time:calendar = "gregorian" ; float swath_band_data(along_track, across_track, band_enum) ; swath_band_data:coordinates = "lon lat time band" ; _______________________________________________ CF-metadata mailing list CF-metadata@xxxxxxxxxxxx http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
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