Basic Information on sigest

Task: sigest
Purpose: Estimate the rms level in an image.
Categories: map analysis

        SIGEST is a Miriad task which attempts to estimate the rms noise
        level in an image. It does this by determining statistics of a
        clipped version of the image data. Based on the statistics of
        clipped Gaussian noise, the rms is then estimated. This
        assumes that the image pixels, after clipping, are dominated by noise.
 
        SIGEST will work poorly on images containing significant sidelobes.

Key: in
        The input image dataset. No default.

Key: clip
        The clip level to use. Pixels are excluded from the calculation
        if their absolute value is greater than the clip value. Ideally
        the clip should be about 2 to 3 times the rms noise level.
        The default uses an initial estimate of the rms to set the clip
        at 2.5 times the rms.

Key: region
        The standard image region of interest of the input. See the help
        on region for more information. The default is the entire image.