[daip] GAL

[Eric Greisen]

It turns out that I am using GAL for my own work at present and so am
better informed than usual.

Note that GAL is used on a first moment image output by XMOM or MOMNT
rather than on a data cube.  Furthermore, that moment image had better
be in velocity units rather than frequency for a number of reasons.
Use ALTSW on your cube if needed to make the freq axis a velocity.
MOMNT will blank with a smoothed image of the cube, XMOM requires
TRANS (to axis order 312) and only applies a flux cutoff on the input
image.  If the blanking is good the two will produce essentially the
same answer.

Eric Greisen