[iaufwg] Final FITS review comments

[Arnold Rots]

William Pence wrote:
> Dear IAU FWG members,
> 
> ...
> 
> List of remaining open issues regarding the FITS Standard document
> ------------------------------------------------------------------
> ...
> 
> 2. from Andreas Wicenec (17 March):
> >The last two sentences in section 3.1 should be dropped, since they
> >are not quite correct and don't add any further information to the 
> >standard. If anything then one may state that 'limitations due to 
> >hardware or software may restrict the  actual size of FITS files'.
> 
> For reference, here are the 2 sentences:
> 
>    "Software packages that read or write data according to this
>    standard could be limited, however, in the size of
>    files that are supported. In particular, some software systems
>    have historically only supported files up to 2^{31} bytes in
>    size (approximately 2.1 GB).
> 
> Response: These 2 sentences provide additional information that may be
> useful to some readers, and it does no harm to leave them in the
> document, even though they are not strictly required to define the FITS
> format.

Note that usually 1 kB is considered to be 2^10 B, 1 MB = 10^20 B, and
1 GB = 10^30 B.
Hence it would have been correct to say that 2^31 bytes is
approximately 2.1*10^9 bytes, but 2^31 bytes is exactly 2 GB.

> 
> ...
> 11. from Ray Norris (17 March)
> >Table 8.5, I think there should be a footnote defining "radio
> >velocity" and "optical velocity", as they do not have a physical basis
> >(but are a computational convenience) and so may not be obvious to a
> >scientist in 100 years time.
> 
> Response:  The following footnote should be added to table 8.5:
> - By convention, the "radio" velocity is given by $c(\nu_0 - \nu)/\nu_0$
> and the "optical" velocity is given by $c(\lambda_0 - \lambda)/\lambda_0$

No!
v_opt = $c(\lambda - \lambda_0)/\lambda_0$

> 
> ...
> 16.  from Mark Calabretta:
> >The new Standard should note any inconsistencies in syntax
> >between previous versions of the Standard, either as an
> >appendix or as footnotes throughout the document.
> 
> I am unsure how to respond to this suggestion.  No one seems to know of
> any specific cases of changed syntax that should be documented, and no
> one has volunteered to take on the task of searching through the
> documents to look for any such cases. I can't gauge how the FWG as a
> whole feels about this issue because there has been so little discussion
> so far.  A couple people (Allen and Shaw) have seemed to question
> whether the Standard is in fact the best place for this type of
> information.  Perhaps it would be more appropriate to put this in a
> separate FITS Implementor's Guide along with other practical guidelines.
> 
> I would like to hear how other members feel about this issue.  Is this
> issue important enough that it must be addressed immediately?  What
> is the scope of changes that should be documented, i.e., would we only
> include any changes that have occurred between versions 1.0 of the
> Standard and the current draft version 3.0, or are we also talking about
> any changes with respect to the original FITS Papers?  Is anyone willing
> to take on this task of making a detailed comparison of the different
> versions to look for changes?  Personally, I would have to say I don't
> really see the urgency in addressing this issue to cause a delay in
> voting on the new standard. But I would like to hear what others think.

I would be in favor of adding an appendix that contains an audit
trail, providing the significant changes between specific versions.
Since an Appendix is not part of the formal standard, it will be
possible to update it without affecting the standard, as we remember
additional items that should be listed.
So: add an audit trail appendix, give it (y)our best shot, but don't
hesitate to update it.

  - Arnold

> 
> Bill
> -- 
> ____________________________________________________________________
> Dr. William Pence                       William.Pence at nasa.gov
> NASA/GSFC Code 662       HEASARC        +1-301-286-4599 (voice)
> Greenbelt MD 20771                      +1-301-286-1684 (fax)
> 
> 
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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 head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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