MAP_PRECIS

      MAP_PRECIS    Real

    Maximum  mismatch in pixel at map edge between the true synthesized beam
    (which would have been computed using the exact channel  frequency)  and
    the  computed  synthesized  beam with the mean frequency of the channels
    sharing the same beam. This is used (with the actual image size) to  de-
    rive  the  actual  number of channels that can share the same beam, i.e.
    the effective value of BEAM_STEP when BEAM_STEP is -1.

    Default is 0.1