[fitswcs] RADESYS = 'GAPPT'

[Steve Allen]

On Wed 2011-03-16T12:31:30 -0700, Rob Seaman hath writ:
> Which is to say that I've had surreal conversations too many times
> about the "meaning" of RA versus TELRA versus the WCS keywords versus
> "reference pixels" versus...

The existing Lick Observatory FITS files contain CRVAL1 and CRVAL2
cards with meanings that correspond to no standard, but which are
essential for interpreting the pixels.  Those cannot be idly removed.

I take both of the above as examples of the motivations Greisen and
Calabretta had when they provided us with 26 alternate WCS versions.
There is room for us all to append our own meanings, precise or not,
but there should not be room for debate on the intended interpretation.

I'm ruminating about best practices for existing systems and
engineering suggestions to include in subsequent ones.

--
Steve Allen                 <sla at ucolick.org>                WGS-84 (GPS)
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