DG_SMOOTH

##
DG_SMOOTH

            DG_SMOOTH
            Smoothes an image using the Conjugate Gradient Algorithm.
            (Author: Didier GIRARD, Groupe d'Astrophysique)

        The  smoothed  image  is  the  equilibrium  state  of  a  thin  flexible
        plate  constrained  to  pass near each height datum by a spring attached
        between it and the plate.  The smoothing is controled by the  "Smoothing
        Parameter" P :
                        P = ( plate stiffness) / ( springs stiffness)
        A low value for P (0.001) means high fidelity to the original  data  and
        should  be used for high signal to noise ratios.  If the data are noisy,
        use higher values of P (0.1 to 10).   The  algorithm  is  iterative  and
        needs  a  work  space equal to 3 input maps.  It usually converges in 10
        iterations, and can be restarted if you save the work files.  Timing  is
        of  the order of 2 seconds of microVAX II CPU time for a 128 by 128 map.
        It takes into account blanked pixels properly.