VOUnits RFC

[Arnold Rots]

I think I would definitely deprecate ta and Ba, not sure about min.
h and yr are fine, as far as I am concerned.
Personally, I find ha a bit obscure and tend to think of it as representing
hectare.
I would prefer cy.
That makes me wonder, what is the SI symbol for are? a or are?

  - Arnold

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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 cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Fri, Jul 26, 2013 at 3:02 PM, Norman Gray <norman at astro.gla.ac.uk> wrote:

>
> Arnold, hello.
>
> On 2013 Jul 26, at 19:29, Arnold Rots <arots at cfa.harvard.edu> wrote:
>
> > This reminded me that I should quote the units allowed in the draft
> > of FITS WCS Paper IV:
> >
> > recommended:
> >
> > s: second
> > d: day (= 86400 s)
> > a: Julian year (= 365.25 d)
> > cy: Julian century (= 100 a)
> >
> > also acceptable:
> >
> > min: minute (= 60 s)
> > h: hour (= 3600 s)
> > yr: Julian year (= a)
> > ta: tropical year
> > Ba: Besselian year
>
> I take I should therefore add these to the FITS 'known units' table in the
> document (and library), as recommended and deprecated, respectively.
>
> Given the language in paper IV section 4.2, I suspect that these are _all_
> in fact 'recommended' units in the sense of this IVOA document (even if
> paper IV would encourage authors to quote times in seconds rather than
> minutes), but that 'a' is preferred to 'yr'.  Does that sound plausible?
>
> The current list of FITS 'known units' was taken from tables 4.1 and 4.2
> in the FITS v3.0 spec (Pence et al., 2010).  Would that plus these units in
> WCS IV be complete?
>
> At present, all of 's', 'd', 'a', 'min', 'h' and 'yr' are mentioned but
> not deprecated, and 'cy', 'ta' and 'Ba' aren't mentioned.  What do you
> think of 'ha' -- hecto-year -- as a century?  The VOUnits document states
> that 'ha' should be interpreted as a century, because the SI document gives
> only rather grudging acknowledgement of the hectare; but that was a toss-up.
>
> All the best,
>
> Norman
>
>
> --
> Norman Gray  :  http://nxg.me.uk
> SUPA School of Physics and Astronomy, University of Glasgow, UK
>
>
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