DEFMAP a structure containing the current values for the Map
SIZE, CELL and FIELD of view, derived from the user prescription
in MAP_SIZE, MAP_CELL and MAP_FIELD.
BEAM_SHAPE[Nw,Nv] is a 2-D array containing the results by UV_STAT
BRIGGS, CELLS, ROBUST, TAPER or WEIGHT. It can be used in scripts
to select the optimal combination of MAP_ROBUST and MAP_UVTAPER
values according to the desired compromise of sensitivity and angular
resolution.
UV_BMIN and UV_BMAX, the min and max baselines