UCD problem in SSA/SpectrumDM

[Keith Noddle]

Hi Alberto,

Following Bruno's recent evaluation of the SSA document highlighting 
among other things a disconnect between the spectrum data model defined 
in SSA and that of the Data Model WG, Mireille and I plan to review SSA 
and see what can be done to reconcile this and other issues. We will 
obviously include your observations below in such an exercise!

Keith.

> 
> Dear DAL chair,
> 
> I'd like to mention a little but annoying problem with
> the instrument bandpass as defined in:
> 
> - Spectrum DM
> - SSA v1.04
> - ssap-keywords.xls
> 
> (see below all references in those documents to the instr.bandpass UCD)
> 
> 
> The problem is that the the wrong UCD is assigned to the central 
> wavelength of the bandpass.
> 
> All documents mention the UCD "instr.bandpass" for the field identified 
> by utype:
> Char.SpectralAxis.Coverage.Location.Value
> 
> This is wrong because the central wavelength of a bandpass is a 
> wavelength, not a bandpass.
> The correct UCD should therefore be:
> 
> em.wl.central;instr.bandpass
> 
> 
> and not just instr.bandpass.
> 
> 
> How easy would be to ammend the SSA document with such an easy change?
> 
> 
> (Without going into too many details, the fact that instr.bandpass is 
> instead used
> for a numeric field (central wavelength) makes the SSA validator fail 
> the test
> for the ESO SSA service, but that is a different issue that I will 
> address within
> a different forum. The problem here is that a wrong UCD is used.).
> 
> Many thanks,
> 
> Alberto
> 
> PS: All references to instr.bandpass in the mentioned documents:
> 
> 
> Appendix D: SSA Data Model Summary:
> -----------------------------------
> 
> DataID.Bandpass | instr.bandpass | Band as in RSM Coverage.Spectral | 
> char | * |
> Char.SpectralAxis.Coverage.Location.Value  |  instr.bandpass |  Spectral 
> coord value |  double *** wrong UCD
> Char.SpectralAxis.Coverage.Bounds.Extent   | instr.bandwidth   | Width 
> of spectrum |  double
>  
> 
> IVOA Spectral Data Model:
> -------------------------
> 
> Spectrum.DataID.Bandpass | instr.bandpass | Band, consistent with RSM 
> Coverage.Spectral | OPT | UNKNOWN |
> Spectrum.Char.SpectralAxis.Coverage.Location.Value | instr.bandpass | 
> Spectral coord value | MAN |     
> <PARAM ID="SpectralLocation" datatype="double" name="SpectralLocation" 
> ucd="instr.bandpass" 
> utype="spec:Spectrum.Char.SpectralAxis.Coverage.Location.Value"
>  value="6515.408759029946">
> 
> 
> 
> ssap-keywords.xls spreadsheet:
> ------------------------------
> 
> Bandpass         Spectrum.DataID.Bandpass  instr.bandpass  Band as in 
> RSM Coverage.Spectral   SPECBAND  char * q                   
> SpectralLocation Spectrum.Char.SpectralAxis.Coverage.Location.Value  
> instr.bandpass  Spectral coord value    SPEC_VAL        double           
> m    q
> 
> 



-- 
Keith Noddle                    Phone:  +44 (0)116 223 1894
AstroGrid Project manager       Fax:    +44 (0)116 252 3311
Dept of Physics & Astronomy     Mobile: +44 (0)7721 926 461
University of Leicester         Skype:  keithnoddle
Leicester                       Email:  ktn at star.le.ac.uk
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