Multi-dimensional Data Access minimal requirements

[Mark Allen]

Hi Arnold,

I’m glad to hear you consider the requirements generally reasonable! 

I’m aware of the discussions about redshift/Doppler and spectral axes. The distinction I make here is that redshift/Doppler velocity is an interpreted coordinate that requires extra information (Doppler definition opt/radio, a redshift, or a reference frequency/wavelength - as you’ve pointed out in those discussions) and that the definition of those extra things is sufficiently complicated to leave it out of this first cut of requirements for data cubes.  Multiple objects, or multiple spectral lines in a given cube come to mind as complications let alone identification of redshifts of individual objects. 

That said, I agree that being able to distinguish different sorts of data cubes in data discovery is important and we should discuss this as part of the next steps - there can be many other cube axes that we would like to be able to query on and I suggest that Redshift/Doppler cube axes be part of a wider consideration of interpreted and derived axes in the next steps.

best regards,
Mark


On 7 Mar 2014, at 16:27, Arnold Rots <arots at cfa.harvard.edu> wrote:

> While appreciative of these requirements that are generally reasonable,
> I have to register my strong objection to its leaving out the Doppler velocity
> (Redshift) axis. I have said this over and over, and will keep repeating it:
> if we don't properly distinguish between the redshift and the spectral axes,
> queries and results will get confused and users annoyed.
> Redshift or Doppler velocity constraints need to be added to Data Discovery
> and to Simple Cutout.
> 
> Cheers,
> 
>   - Arnold
> 
> -------------------------------------------------------------------------------------------------------------
> Arnold H. Rots                                          Chandra X-ray Science Center
> Smithsonian Astrophysical Observatory                   tel:  +1 617 496 7701
> 60 Garden Street, MS 67                                      fax:  +1 617 495 7356
> Cambridge, MA 02138                                         arots at cfa.harvard.edu
> USA                                                   http://hea-www.harvard.edu/~arots/
> --------------------------------------------------------------------------------------------------------------

Mark Allen
mark.allen at astro.unistra.fr

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