[fitswcs] Status of WCS negotiations

[Doug Mink]

Eric Greisen wrote:
>      Don's use of the PROJPn keyword makes the point that we need a
> better keyword for this purpose.  I propose CPnn_iiV where CP means
> coordinate parameter, nn (1 or 2 digit no leading zero) is the axis
> number, ii (1 or 2 digits no leading zero) is the parameter number and
> V is the version code (blank for main, A-Z for secondary
> descriptions).  This general word allows us to propose projection-like
> parameters for e.g. velocity axes in some future agreement.  For axis
> pairs (longitude-latitude) we will have to agree on which axis is
> given the CPs and I would suggest the latitude (in honor of the by now
> much deprecated CROTA2).  The omission of leading zeros (forcing the _
> separator) is in line with the NOST standard as is the limit to
> upper-case letters in the version code.

I agree with Eric's proposed use of CPnn_iiV.  For my
polynomial-corrected TAN projection, I am using COnn_ii for similar
reasons.  It should be
directly translatable into a standard using CPnn_iiV, and I already
have a program in the WCSTools package, keyhead, for changing header
keyword names in bulk.

-Doug Mink