[fitswcs] NAXIS vs. WCSDIM

[Arnold Rots]

I remain unconvinced by Doug's arguments.  If I understand it
correctly, acceptance of the WCSDIM keyword will not change anything
without substantial software changes: those who currently use
degenerate axes will be able to continue to use them but not
understand the WCSDIM convention, and those who do not currently use
degenerate axes will adopt WCSDIM but still not be able to read
interpret images which use degenerate axes.

Admittedly, nothing lost - but nothing gained, either, and that seems
a poor basis for designing standards.  Considering that there is a
perfectly acceptable standard that allows full WCS description of
images through the use of degenerate axes, and considering that a
substantial part of the community (and it is not just the radio
community) has been using that device successfully for many years, I
would suggest that non-conforming part of the O/IR community (and,
again, it is not the entire O/IR community) bite the bullet, rather
than go off in a direction that is not compatible and will remain not
compatible with the rest of the community.

L3et me stress again that the use of degenerate axes is not tantamount
to overloading NAXIS.  As a matter of fact, the term "degenerate axis"
is unnecessarily pejorative: there is no reason why a single-pixel
axis should not be considered on par with multi-pixel axes.  Neither
does the comment that the simplicity of 1-D and 2-D images is lost
carry much weight: the raison d'etre for software is to make
complicated things look simple to the user.  Let the software deal
with it.

  - 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 81                              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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