[fitswcs] WCS documents

[William Pence]

Peter Teuben's suggestion, below, to add more examples to the current
keyword units proposal highlights the awkwardness of the current situation:
the convention for enclosing the keyword units in square brackets is being
defined in one place (proposed to be added to section 5.3 of the FITS
Standard), but recommendations for the contents of the units string itself
are defined in another place (Appendix B of WCS Paper I).   I think these
proposals need to be merged into a common proposal that would replace the 2
sentences that are currently in the Units section 5.3 in the FITS Standard. 
Section 5.3 is the logical place to put all units-related information; other
sections of the Standard which need to deal with units (e.g., the discussion
of the TUNITSn keyword in sections 8.1.2 and 8.3.2) simply refer back to
section 5.3.  I think it is a bit inappropriate to have the discussion of
the allowed units strings only in the WCS paper, because this is relevant in
many other contexts that have nothing to do with WCS.

So, I propose the following:  We remove appendix B from the WCS paper, merge
it with the current keyword units proposal at
http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/keywordunits.html, and submit
this as a separate proposal to replace the current section 5.3 in the FITS
Standard. 

This has a number of advantages:

1.  It simplifies the WCS paper.  All the WCS paper needs to state is:
"Units must follow the prescriptions of section 5.3 of the FITS Standard". 
This will also remove any debate about the allowed units strings when the
WCS papers come up for a vote.  I believe Appendix B could be removed from
Paper I with little or no change to the rest of the paper and thus should
not introduce any additional delay in getting the WCS Papers approved.  I
may have missed it, but I didn't see any reference to Appendix B in the body
of the paper.  

2.  This new Units proposal can be prepared and submitted to the FITS
committees very quickly.  Someone just needs to merge the text from the 2
separate proposals, and perhaps make a few editorial changes to make the
language suitable for inclusion in the FITS Standard.  Eric is probably the
logical person to do this, but I am certainly willing to help.

Does anyone else think this is a good idea??

-Bill

Peter Teuben wrote:
> 
> Bill,
>   do we have a good link to the IAU Style Manual. I don't even think I have
> a copy of it, despite that we often talked about it in the NOST document(s).
> 
> One thing I was wondering about is the academic possibility that there
> is a units which requires a lot of characters, so we could run out of space.
> 
> It would be good to add one or two more example or more complex variables,
> e.g. G (gravitational constant) and something with a bit more "math" to
> show the syntax.
> 
> Secondly, what is the requirement if something is dimensionless. Leave it out,
> or use [] explicitly? THings that just came to mind as I revisited this page.
> 
> -peter
> 
> On Wed, 10 Oct 2001, William Pence wrote:
> 
> > Eric and Mark,
> >
> > As a reminder of what was mentioned at the FITS BoF at the ADASS meeting, a
> > proposal for how to specify the physical units of a keyword value has been
> > submitted to the chair of the North American FITS committee for
> > consideration.  The full proposal can be viewed at:
> >
> > http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/keywordunits.html.
> >
> > It was suggested that Appendix B in your first WCS paper might be revised to
> > also mention this keyword units convention.
> >
> > In fact, once your WCS papers are approved and become part of the FITS
> > Standard, it might make sense to move most or all of your appendix B into
> > what is now section 5.3 (the Units section) of the FITS Standard.
> >
> > regards,
> > Bill
> > --
> > ____________________________________________________________________
> > Dr. William Pence                          pence at tetra.gsfc.nasa.gov
> > NASA/GSFC Code 662         HEASARC         +1-301-286-4599 (voice)
> > Greenbelt MD 20771                         +1-301-286-1684 (fax)
> >

-- 
____________________________________________________________________
Dr. William Pence                          pence at tetra.gsfc.nasa.gov
NASA/GSFC Code 662         HEASARC         +1-301-286-4599 (voice)     
Greenbelt MD 20771                         +1-301-286-1684 (fax)