[fitswcs] Polynomial projection

[Mark Calabretta]

On Fri 2005/04/29 11:54:35 -0400, William Thompson wrote
in a message to: fitswcs at nrao.edu

>The new projection would be -PLY, and would be defined such that
>
>	S = S_r + w + A_2*w^2 + A_3*w^3 + ... + A_20*w^20

Historically, early drafts of Paper III contained a Sect. 2.2, "Higher
Order Corrections", which described such a mechanism for all spectral
coordinate types.  After 2001/07/04, when it was decided that
distortions should be handled separately, the text of this section
was replaced with a forward reference to Paper IV, and likewise the
polynomial extension to the TAN projection in Paper II was removed.
After 2001/10/29 the whole of Sect. 2.2 was removed from Paper III lest
it preempt the methods of Paper IV; only a reference to Paper IV was
left in the introduction.  The rationale was that the distortion
correction is supposed to be "small" and optional and that it would be
better to do it properly and just in one place.

Mark Calabretta
ATNF