Subject: Re: wcs.ps

From: Don Wells <dwells at cv.nrao.edu>
Date: Wed, 31 Mar 1999 12:35:07 -0500

Lucio Chiappetti writes:
 > On Wed, 31 Mar 1999, Francois Ochsenbein wrote:
 > 
 > > Appendix B with the OGIP conventions on units in FITS that,
 > > as far as I know, were never approved (was WCS approved ?)
 > 
 > a statement on the official approval status of both would be appreciated.

The FITS WCS conventions beyond those described in the earliest FITS
papers have not been subject to a vote by any of the FITS committees. 
Therefore, the current NOST FITS standard does not discuss them.

Conventions on units for FITS beyond those recommended in the FITS
papers have not been subject to a vote by any of the FITS committees. 
Therefore, the current NOST FITS standard says in its section 5.3 that
units should conform to the IAU style manual and 'for angular
measurements given as floating point values and specified with
reserved keywords, degrees are the recommended units'. 

The OGIP conventions on units are an agreement among certain
high-energy astrophysics data groups. The 'wcs.ps' draft is proposing
that a version of them become a recommended practice to augment the
IAU Style Manual rules. The units conventions used by the data centers
(CDS, ADC, etc) for data tables should be regarded as another draft
proposal for FITS.  I expect that a merger of the two sets of
conventions would be best; see:

http://vizier.u-strasbg.fr/doc/catstd-3.2.htx
http://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/general/ogip_93_001/ogip_93_001.html
    
The current negotiation of the WCS conventions for FITS is an
opportunity to agree on a recommended practice for interchanging
computer character string representations of units, a problem which
the IAU Style Manual did not address.

-Don
-- 
  Donald C. Wells      Scientist - GBT Project        dwells at nrao.edu
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