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NRAO Home > CASA > CASA Task Reference Manual |
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0.1.98 sdimprocess
Requires:
Synopsis
Task for single-dish image processing
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 FFT-based
’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.
Arguments
Inputs |
| ||
infiles |
| list of name of input SD images (FITS or CASA image)
| |
| allowed: | any |
|
| Default: | variant ” | |
mode |
| image processing mode
| |
| allowed: | string |
|
| Default: |
| |
numpoly |
| order of polynomial fit for Pressed-out method
| |
| allowed: | int | |
| Default: | 2 |
|
beamsize |
| beam size for Pressed-out method | |
| allowed: | double |
|
| Default: | variant 0.0 | |
smoothsize |
| size of smoothing beam for Pressed-out method
| |
| allowed: | any |
|
| Default: | variant 2.0 | |
direction |
| scan direction
(p.a.) counterclockwise from the horizontal axis in unit
of degree
| |
| allowed: | any |
|
| Default: | variant
|
|
maskwidth |
| mask width for Basket-Weaving (on percentage)
| |
| allowed: | any |
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| Default: | variant 1.0 |
|
tmax |
| maximum threshold value for processing
| |
| allowed: | double |
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| Default: | 0.0 |
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tmin |
| minimum threshold value for processing
| |
| allowed: | double |
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| Default: | 0.0 |
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outfile |
| name of output file
| |
| allowed: | string |
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| Default: |
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overwrite |
| overwrite the output file if already exists
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| allowed: | bool |
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| Default: | False |
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void
Example
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Keyword arguments
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infiles -- name or list of names of input SD (FITS or CASA) image(s)
mode -- image processing mode
options: ’basket’ (FFT-based Basket-Weaving),
’press’ (Pressed-out method)
default: ’basket’
>>>mode expandable parameter
direction -- scan direction (p.a.) counterclockwise from the
horizontal axis in unit of degree.
default: []
example: direction=[0.0, 90.0] means that the first image
has scan direction along longitude axis while the
second image is along latitude axis.
maskwidth -- mask width for Basket-Weaving on percentage
default: 1.0 (1.0% of map size)
numpoly -- order of polynomial fit in Presssed-out method
default: 2
beamsize -- beam size for Pressed-out method
default: 0.0
example: beamsize=10.0 is interpreted as ’10arcsec’.
beamsize=’1arcmin’ specifies beam size as
quantity.
smoothsize -- smoothing beam size in Pressed-out method.
if numeric value is given, it is interpreted in unit
of beam size specified by the parameter beamsize
default: 2.0
example: smoothsize=2.0 means that smoothing beam size is
2.0 * beamsize.
smoothsize=’1arcmin’ sets smoothsize directly.
tmax -- maximum threshold value for processing
default: 0.0 (no threshold in maximum)
example: 10.0 (mask data larger value than 10.0)
tmin -- minimum threshold value for processing
default: 0.0 (no threshold in minimum)
example: -10.0 (mask data smaller value than -10.0)
outfile -- name of output file. output file is in CASA image format.
default: ’’ (use default name ’sdimprocess.out.im’)
example: ’output.im’
overwrite -- overwrite the output file if already exists
options: (bool) True, False
default: False
-----------
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 FFT-based
’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 maskwidth 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. To do this, smoothsize should
be specified as string that consists of a numerical value and an unit
(e.g. ’10.0arcsec’). A value of beamsize will be ignored in this case.
Another way to specify smoothing size is to set an observed beam size
and indicate smoothing size as a scale factor of the observed beam
size. 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 ’arcsec’. 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, and its unit is degree. 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.
More information about CASA may be found at the
CASA web page
Copyright © 2016 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
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