[fitswcs] Multiple WCS implementation in WCSTools

[Doug Mink]

While we don't seem to have full agreement about all of the proposed FITS WCS
standard, one new feature for which several people have expressed a need is
the ability to have several sets of WCS keywords in a single FITS header.  I
have implemented this feature in the latest release of WCSTools, shaken out
at least some of the bugs, and released it at

 ftp://cfa-ftp.harvard.edu/pub/gsc/WCSTools/wcstools-2.9.2.tar.gz

WCSTools 2.9 implements the use of multiple world coordinate systems, with the
WCS to which a keyword applies designated by a suffixed upper-case alphabetic
character. 

Thus CTYPE1 applies to the default WCS, which may be named using WCSNAME.
A second WCS could use keywords such as CTYPE1A and WCSNAMEA. Up to 27 (no
suffix, A-Z) different sets of WCS keywords may be specified. 

In the WCSTools programs, the WCS to be used is specified by adding %WCSNAME
to the end of a filename specified on the command line. This is added after
the extension of a multi-extension FITS image is specified: 

fitsfile,extension_name_or_number%WCS_name_or_letter

The imwcs program always fits the default (no suffix) keywords. 

An additional nonstandard feature has been added, the keyword WCSDEPx, which
is set equal to the name of a WCS which would be found in a WCSNAMEx keyword
value or a single character which is assumed to be the suffix for the WCS.
WCSDEPx implementation was pretty easy, but it has not been tested.

Source code for the WCS subroutines are available in

 ftp://cfa-ftp.harvard.edu/pub/gsc/WCSTools/wcssubs-2.9.2.tar.gz

I have used these subroutines in a new version of SAOimage, source for
which can be found at

 ftp://cfa-ftp.harvard.edu/pub/gsc/SAOimage/saoimage-1.29.2.tar.gz

Alpha and Solaris binaries are in the same directory.

I will try to get one or both of the sample files Steve Allen passed on to me
and some sample usage online this week.  All that is on the SAOimage web site
now is the above description.

Let me know what you think and tell me about any problems you find.

-Doug Mink