WCS questions

[Mark Calabretta]

On Thu 1996/12/19 16:22:29 GMT, William Thompson wrote
in a message to: fitsbits at fits.cv.nrao.edu

>I'm confused here.  My reading of the WCS document is that the PC matrix must
>agree with the CDELT, CRVAL, and CTYPE values.  Or did you mean CmELT, etc.?

WCS is defined as a chain of independent algorithms as described in fig. 1 of
the draft.  What does it mean to say that one step in this chain "agrees" with
another?  The suggestion is to tap into the intermediate products of that
chain.

One point which does need clarifying though is whether the PC matrix is or is
not used in conjunction with the secondary axis descriptors.  I have assumed
it is but the current draft does not say explicitly.  Image rotation would be
the main issue here.

Mark Calabretta
ATNF