[fitsbits] Primary & Alternate WCS Keyword Order

[Lucio Chiappetti]

What Bill did for the verifier (excerpt below) appears consistent with the 
LETTER of the standard, which talks only of the position of WCSAXES and 
not of WCSAXESa

I have re-read WCS papers I and II, The case for WCSAXES <> NAXIS and for 
degenerate axes is mentioned in some detail in paper I, and there is an 
even more detailed example for a long slit case in paper II (which however 
does not mention WCSAXES at all). The requirement on the position of 
WCSAXES (alone) is in paper I.

So the question is whether we should

(a) do any amendment to the standard (releasing the positioning 
requirement),

(b) issue an explanatory note (in the sense that the requirement applies 
to WCSAXES only, while for WCSAXESa is a mere recommendation for the order 
inside WCS a alone),

(c) do nothing and consider implicit was said in (b)


On Thu, 28 Jun 2012, William Pence wrote:

> Based on the lengthy discussion of this issue here, I have modified the
> on-line FITS file verifier at http://fits.gsfc.nasa.gov/fits_verify.html
> to temporarily disabled any checks on the position of the WCSAXESa

> For now at least, the FITS verifier still requires that the WCSAXES 
> keyword itself (without an alternate suffix letter) appear before any 
> other WCS keyword, but the alternate WCSAXESa keywords may appear 
> anywhere.

-- 
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Lucio Chiappetti - INAF/IASF - via Bassini 15 - I-20133 Milano (Italy)
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