[CF-metadata] New CoordinateType: Spectral?

[rho...@excaliburlabs.com]

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  

 
___
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata

Re: [CF-metadata] New CoordinateType: Spectral?

[Lowry, Roy K.]

Hello Randy,

If doing this, please make it clear that by 'Spectral' you mean 'wavelength 
spectral'.  There are other types of spectra, such as frequency (used for wave 
spectra) and size (used optical plankton counters and other particle sizers).

Cheers, Roy.

Please note that I now work part-time from Tuesday to Thursday.  E-mail 
response on other days is possible but not guaranteed!

From: CF-metadata [mailto:cf-metadata-boun...@cgd.ucar.edu] On Behalf Of 
rho...@excaliburlabs.com
Sent: 10 April 2013 14:20
To: cf-satell...@unidata.ucar.edu; cf-metadata@cgd.ucar.edu
Subject: [CF-metadata] New CoordinateType: Spectral?


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




This message (and any attachments) is for the recipient only. NERC is subject 
to the Freedom of Information Act 2000 and the contents of this email and any 
reply you make may be disclosed by NERC unless it is exempt from release under 
the Act. Any material supplied to NERC may be stored in an electronic records 
management system.
___
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata