Source code for casatasks.single.sdfixscan

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# stub function definition file for docstring parsing
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[docs]def sdfixscan(infiles, mode='fft_mask', numpoly=2, beamsize='0.0', smoothsize='2.0', direction='', maskwidth='1.0', tmax=0.0, tmin=0.0, outfile='', overwrite=False): r""" Task for single-dish image processing [`Description`_] [`Examples`_] [`Development`_] [`Details`_] Parameters - infiles_ (variant) - list of name of input SD images (FITS or CASA image) - mode_ (string='fft_mask') - image processing mode ["fft_mask", "model"] .. raw:: html <details><summary><i> mode = fft_mask </i></summary> - direction_ (variant='') - scan direction (p.a.) counterclockwise from the horizontal axis in unit of degree - maskwidth_ (variant='1.0') - mask width for Basket-Weaving (on percentage) .. raw:: html </details> .. raw:: html <details><summary><i> mode = model </i></summary> - numpoly_ (int=2) - order of polynomial fit for Pressed-out method - beamsize_ (variant='0.0') - beam size for Pressed-out method - smoothsize_ (variant='2.0') - size of smoothing beam for Pressed-out method - direction_ (variant='') - scan direction (p.a.) counterclockwise from the horizontal axis in unit of degree .. raw:: html </details> - tmax_ (double=0.0) - maximum threshold value for processing - tmin_ (double=0.0) - minimum threshold value for processing - outfile_ (string='') - name of output file - overwrite_ (bool=False) - overwrite the output file if already exists [True, False] .. _Description: Description Task **sdfixscan** is used to remove a striping pattern generated along the scan direction in raster scan data. By default, the scanning noise is removed using the FFT-based 'Basket-Weaving' method [1]_ that requires multiple images observed over exactly the same area with a different scanning direction. When doing 'Basket-Weaving', you can mask small structures and protect them using the *maskwidth* parameter. If only one image is available, the 'Pressed-out' method [2]_ can be used to remove the scanning effect. For 'Basket-Weaving', scans must have been conducted in at least two different directions. Normally, the scanning direction should be specified for each input image. As *direction* parameters, you should specify the angles perpendicular to the scan directions in units of degrees. The angle is defined in the counterclockwise direction from the x-axis. It removes scan noise by masking wave components perpendicular to the scan direction in the Fourier domain. Scan noise and striation structures appear as band-like artifacts in the Fourier transformed data. The parameter *maskwidth* controls the width of the mask in Fourier space and is defined as a percentage in the Fourier domain (*maskwidth = 10* means masking a region of 10% width in Fourier space). In the perfect case, where scan noise is an ideal striation without structure in the direction perpendicular to scan direction, the scan noise can be removed by specifying a small value for *maskwidth* (ex. *maskwidth = 1*). In the actual case, *maskwidth* should be set to some larger number, since scan noise also has some structure in the direction perpendicular to the scanning direction. Larger *maskwidth* values may also remove the emission from the scientific target at the same time, so careful adjustment and characterization by the user is necessary. .. note:: **NOTE**: Such masks are applied for each input scan image and the combined image is returned. If the size of the mask is large, the improvements to the noise level by combining images becomes small, since a smaller amount of data is subject to the processing. And note that 'Basket-Weaving' mode supports combining orthogonal scan noise images only (It is possible, but, at least, this function has not been tested enough). For 'Pressed-out', the scanning must be in a single direction. There are two ways to specify the size of the smoothing beam used for this process. One is to specify smoothing size directly. To do this, *smoothsize* should be specified as a string of a numerical value and a unit (e.g. '10.0arcsec'). The value of *beamsize* will be ignored in this case. The other way is to set smoothing size as a scale factor of the observed beam size. In this case, *beamsize* is interpreted as the observed beam size, and *smoothsize* is the scale factor. If the *beamsize* is provided as a float value, its unit is assumed to 'arcsec'. It is also possible to set the *beamsize* as a string consisting of the numerical value and the unit. The *smoothsize* must be a float value. The *infiles* must be an image (CASA or FITS), and does not work with MS or Scantable. The *direction* is an angle with respect to horizontal, in units of degrees. Preferred entries should range from 0.0 to 180.0 degrees. The *tmax* and the *tmin* parameters are used to specify a threshold that defines a range of spectral values used for processing. Data values larger than *tmax* or smaller than *tmin* will be excluded from the processing. The default (0.0) is to apply no threshold. The *outfile* specifies an output CASA image name. If *outfile* is empty, the default name ('sdfixscan.out.im') will be used. .. rubric:: Bibliography .. [1] Emerson & Grave 1988, A&A, 190, 353 `ADS <https://ui.adsabs.harvard.edu/abs/1988A%26A...190..353E/abstract>`__ .. [2] Sofue & Reich 1979, A&AS, 38, 251 `ADS <https://ui.adsabs.harvard.edu/abs/1979A%26AS...38..251S/abstract>`__ .. _Examples: Examples Examples for 'Basket-Weaving' :: sdfixscan(mode='fft_mask', infiles=['scan_0deg.im', 'scan_90deg.im'], direction=[0., 90.], maskwidth=5.0, outfile='basket_0_90.im') sdfixscan(mode='fft_mask', infiles=['scan_30deg.im', 'scan_120deg.im'], direction=[30., 120.], maskwidth=10.0, outfile='basket_30_120.im') Example for 'Pressed-out' :: sdfixscan(mode='model', infiles='scan_0deg.im', direction=90., smoothsize='100arcsec', outfile='press_0.im') .. _Development: Development No additional development details .. _Details: Parameter Details Detailed descriptions of each function parameter .. _infiles: | ``infiles (variant)`` - list of name of input SD images (FITS or CASA image) .. _mode: | ``mode (string='fft_mask')`` - image processing mode .. _numpoly: | ``numpoly (int=2)`` - order of polynomial fit for Pressed-out method .. _beamsize: | ``beamsize (variant='0.0')`` - beam size for Pressed-out method .. _smoothsize: | ``smoothsize (variant='2.0')`` - size of smoothing beam for Pressed-out method .. _direction: | ``direction (variant='')`` - scan direction (p.a.) counterclockwise from the horizontal axis in unit of degree .. _maskwidth: | ``maskwidth (variant='1.0')`` - mask width for Basket-Weaving (on percentage) .. _tmax: | ``tmax (double=0.0)`` - maximum threshold value for processing .. _tmin: | ``tmin (double=0.0)`` - minimum threshold value for processing .. _outfile: | ``outfile (string='')`` - name of output file .. _overwrite: | ``overwrite (bool=False)`` - overwrite the output file if already exists """ pass