MOSAIC

        [CLEAN\]MOSAIC [?| [CenterX CenterY UNIT] [ANGLE Angle]]

    List and Control the Mosaic processing mode.  Switching between Single-Field
    and Mosaic processing is automatic,

    MOSAIC ? lists the current Mosaic status.

    MOSAIC ON and MOSAIC OFF are obsolete and provided only for backward compat-
    ibility with older syntax.

    MOSAIC with no argument, or with coordinates and/or  orientation,  activates
    the SAULT method.

    Two different Mosaicing processing method exist.  The default one, the GUETH
    mode,  is  based  on  the Gueth, Guilloteau & Viallefond method. It uses and
    produces Primary and Dirty beams of the same sizes as the Sky mosaic.

    The alternative one, the SAULT mode, can only be activated by using the  MO-
    SAIC  command  (with none of the ?, ON or OFF arguments). It uses the method
    published by  Sault, Staveley-Smith and  Brouw  AA  Supp  Ser  120,  375-384
    (1995).   In the Sault et al method, each field is imaged with a smaller map
    size than the Sky mosaic, before being combined together.  This mode is more
    suited for large mosaics, being faster and more accurate (less edge  distor-
    tion effects) than the Gueth et al method.

    The  SHOW MOSAIC command will display the mode characteristics.  As for com-
    mand UV_MAP, variable MAP_CENTER can be used to specify the  Mosaic  center,
    unless the optional arguments are specified. Otherwise, the Mosaic center is
    derived from the pointing positions.

    Once  the  MOSAIC command has been used to select the SAULT mode, only a new
    READ UV command can reset the default mosaic mode so far.   The  syntax  may
    evolve to provide more flexibility.