next up previous contents index
Next: NOISE_SMOOTH Up: Smoothing Tasks Previous: DG_SMOOTH   Contents   Index



    This  task performs a 2D smoothing by an elliptical gaussian. If the in-
    put file is a 3D cube (or 4D hypercube), the 2D gaussian is applied  re-
    peatedly  on  the first 2 dimensions (i.e. each velocity plane for a LMV

    The algorithm works in the Fourier plane and the first 2 dimensions  (in
    pixels) should therefore be powers of two (but need not be equal). It is
    much faster than the equivalent sky plane algorithm, but you should  be-
    ware  of  aliasing  effects when the size of the convolving gaussian be-
    comes a sizeable fraction of the map (say 30%).

    Note also that, because of the round trip  in  the  Fourier  plane,  the
    blanking  values  can  NOT be ignored. This means that each pixel with a
    blanking value will contribute (pollute) the overall smoothed  image  in
    return. In other words, you should avoid images with blank values, or at
    least, set them to a reasonable dummy background value (e.g. 0).

Gildas manager 2020-09-28