[daip] AIPS Mosaic Sensitivity

[Eric Greisen]

VTESS, UTESS, LTESS, STESS are not smart enough to do geometry and the
like.  Instead one must use other aips tasks first to create one image
on the desired (total mosaic) output image size and geometry.  Then
that is used as the template image in HGEOM or OHGEO to make N-1 more
large images each with 1/Nth the area actually filled in with data.
Then these tasks can add up all the images with beam correction etc
and do their thing.

FLATN does the OHGEO operation on the fly and understands the
coordinates of the input images (xTESS do not).

The TESS tasks should test the inputs to see if they meet their needs
and die if not.  Fixing ignorant tasks (e.g. all the uv tasks that
ignore SN and FG tables as well as these TESS tasks) and defending
their ignorance against users' assumptions of intelligence is going to
occupy me for a good bit of the next several months.

Eric Greisen