PLANE

##
PLANE

            PLANE

        This is a simple task that subtracts a plane from an  image.  The  plane
        is determined by least square fitting through all non-blanked pixels  of
        the  original map, weighted by a weight image. The latter can be used to
        account for a non uniform signal to noise ratio, but is more  frequently
        used to ignore some areas (typically the sources) in the fit.

        It  supersedes  an older obsolete version (still available as PLANE_OLD)
        which fitted a plane through 3 points of the input image.