sdimprocess

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8.2.1.18 sdimprocess

Keyword arguments:
infiles -- name of input SD (FITS or CASA) image
mode -- processing mode
        default: ’basket’
        options: ’basket’, ’press’

    >>>mode expandable parameter
         direction -- scan direction in unit of degree
             default: []
             example: [0.0,90.0]
         masklist -- mask width for Basket-Weaving on percentage
             default: 1.0 (1.0\% of map size)
         numpoly -- order of polynomial fit in Presssed-out
             default: 2
         beamsize -- beam size
             default: 0.0
             example: 10.0 (interpreted as ’10arcsec’), ’1arcmin’
         smoothsize -- smoothing beam in Pressed-out
             default: 2.0 (interpreted as 2.0 * beamsize)
             example: ’1arcmin’ (set smoothsize directly)

tmax -- maximum value used for process
        default: 0.0 (no threshold in maximum)
        example: 10.0 (mask data larger value than 10.0)
tmin -- minimum value used for process
        default: 0.0 (no threshold in minimum)
        example: -10.0 (mask data smaller value than -10.0)
outfile -- output CASA image name
        default: ’’ (use default name)
        example: ’output.im’
overwrite -- overwrite option for outfile
        default: False (not overwrite)
        options: True, False
        example: if True, existing file will be overwritten

DESCRIPTION:

Task sdimprocess is used to remove a scanning noise that appears as a striped noise pattern along the scan direction in a raster scan data.

By default, the scanning noise is removed by using the ’Basket-Weaving’ method (Emerson & Grave 1988) that requires multiple images that observed exactly the same area with different scanning direction. If only one image is available, the ’Pressed-out’ method (Sofue & Reich 1979) can be used to remove the scanning effect.

For ’Basket-Weaving’, scanning directions must have at least two different values. Normally, the scanning direction should be specified for each input image. Otherwise, specified scanning directions will be used iteratively. The masklist is a width of masking region in the Fourier plane. It is specified as a fraction (percentage) of the image size.

For ’Pressed-out’, the scanning direction must be unique. There are two ways to specify a size of smoothing beam used for process. One is to specify smoothing size directly, where smoothsize is specified as string that consists of a numerical value and an unit (e.g. ’10.0arcsec’). The value of beamsize will be ignored in this case. Another way to specify smoothing size is to set an observed beam size and indicate them smoothing size as a scale factor of the observed beam. In this case, the beamsize is interpreted as the observed beam size, and the smoothsize is the scale factor. If the beamsize is provided as float value, its unit is assumed to have ’arcsec’ units. It is also possible to set the beamsize as string consisting of the numerical value and the unit. The smoothsize must be float value.

The infiles only allows an image data (CASA or FITS), and does not work with MS or Scantable. The direction is an angle with respect to the horizontal direction in degree units. Any value may be interpreted properly, but the value ranging from 0.0 to 180.0 will be secure. The tmax and the tmin is used to specify a threshold that defines a range of spectral values used for processing. The data point that has the value larger than tmax or smaller than tmin will be excluded from the processing. The default (0.0) is no threshold. The outfile specifies an output CASA image name. If the outfile is empty, the default name (’sdimprocess.out.im’) will be used.

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