[fitswcs] Detector distortion correction representations in FITS

[Doug Mink]

I'll just toss out one more thing we've been bandying about: dependent
WCS projections.  I'm in the process of implementing multiple WCS's as
per the proposed standard, and we at CfA were wondering whether, since
one of the possible WCS's would be pixel to focal plane, another could
be focal plane to sky, where a new keyword would note that the second
projection used the output of the first.  Then the pre-sky projection
polynomial would be explicitly defined as a pixel correction.  What do
people thing of this idea in general as a use for multiple WCS's?

-Doug Mink (who is testing an implementation of single, multiple named WCS's)