MAP_CONTINUUM GLOBAL

        [ADVANCED\]MAP_CONTINUUM [DIRTY|CLEAN|Other] /METHOD  GLOBAL  [Threshold
    [Nhisto]]

      Compute  the  integrated spectrum (over the region specified by CENTER and
    SIZE variables), and delineate the line-free region by Gaussian fitting  the
    histogram of the spectrum intensity.
      The  optional arguments control the algorithm. Threshold is clipping level
    in sigma units: values in range 2.5 - 5 are usable (default 3.5).  Nhisto is
    the number of histogram bins. The default is to adjust this number depending
    on the number of channels in the data. This is the same algorithm as used in
    UV_CONTINUUM, or in a per pixel mode by the GAUSS method.

      The continuum is then derived by integrating  in  the  line-free  regions.
    This  method  is fast, and gives a uniform noise since the same channels are
    used for all pixels.  It may be inaccurate into several ways:
    - Regions with strong broad line may still be contaminated by emission  from
    the line wings
    - The same applies to regions with line confusion.
    -  Continuum emission in regions with no line emission is not derived to the
    maximum sensitivity. This can be an issue in case of line confusion at  some
    positions.