Feedbacks about AVM tags in Aladin

[Doug Mink]

It was interesting to hear about Pierre's problems with AVM tags, which
I had hoped to add support for in WCSTools.  Our default way of dealing
with WCS in JPEG images--and GIFs and PNGs for that matter--has been to
simply extract the FITS header using WCSTools imhead -f (which preserves
all of the blanks and keeps 2880-byte blocks) and append it to the JPEG
file after other processing (which hopefully preserves pixel locations)
has been completed.  The WCSTools header reading software knows to look
at the end of a GIF, JPEG, or PNG file for the FITS header for pixel to
WCS or WCS to pixel conversion or WCS coverage computation.  This may
not be a good standard, but it is a convenient convention and is
independent of AVM standard changing.  In addition, *all* of the header
information is present, so you can find out other things about the image
than its WCS.  I added this feature in version 3.6.4, in May 2006, but I
haven't publicized it very much as it is more a convenience than a
standard, but at least it is a stable convenience!

For a future standard, I think it is important to have a way to put the
entire FITS header, or a reasonably inclusive subset, in any
astronomical image.

-Doug Mink
  Telescope Data Center
  Smithsonian Astrophysical Observatory
  Cambridge, MA USA