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NRAO Home > CASA > CASA Task Reference Manual |
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0.1.120 simanalyze
Requires:
Synopsis
image and analyze measurement sets created with simobserve
Description
This task is for imaging and analyzing measurement sets (MSs) simulated with
simobserve or simalma.
Arguments
Inputs |
| ||
project |
| root prefix for input and output file names. This must be
the directory of results generated by running simobserve
or simalma. In particular project∕project.skymodel will
be required in order to compare output and input
images.
| |
| allowed: | string |
|
| Default: | sim |
|
image |
| (re)image project. * .mstoproject.image
| |
| allowed: | bool | |
| Default: | True |
|
imagename |
| simulation output image to analyze (default = first
$project/*.image found)
| |
| allowed: | string |
|
| Default: | default |
|
skymodel |
| skymodel image to analyze (the .skymodel image created
by simobserve or simalma and used by one of those
tasks to create an MS; if unspecified, will try to find one
similar to your specified output image name)
| |
| allowed: | string |
|
| Default: |
|
|
vis |
| Measurement Set(s) to image
| |
| allowed: | string |
|
| Default: | default | |
modelimage |
| lower resolution prior image to use in clean e.g. existing
total power image
| |
| allowed: | string |
|
| Default: |
|
|
imsize |
| output image size in pixels (x,y) or 0 to match model
| |
| allowed: | intArray |
|
| Default: | 00 |
|
imdirection |
| set output image direction, (otherwise center on the
model)
| |
| allowed: | string |
|
| Default: |
| |
cell |
| cell size with units e.g. ”10arcsec” or ”” to equal model
| |
| allowed: | string |
|
| Default: |
|
|
interactive |
| interactive clean? (make sure to set niter>0 also)
| |
| allowed: | bool | |
| Default: | False |
|
niter |
| maximum number of iterations (0 for dirty image)
| |
| allowed: | int | |
| Default: | 0 |
|
threshold |
| flux level (+units) to stop cleaning
| |
| allowed: | string |
|
| Default: | 0.1mJy |
|
weighting |
| weighting to apply to visibilities. briggs will use
robust=0.5 | |
| allowed: | string |
|
| Default: | natural |
|
mask |
| Cleanbox(es), mask image(s), region(s), or a level
| |
| allowed: | any |
|
| Default: | variant
|
|
outertaper |
| uv-taper on outer baselines in uv-plane
| |
| allowed: | stringArray |
|
| Default: |
|
|
pbcor |
| correct the output of synthesis images for primary beam
response?
| |
| allowed: | bool |
|
| Default: | True |
|
stokes |
| Stokes params to image
| |
| allowed: | string |
|
| Default: | I |
|
featherimage |
| image (e.g. total power) to feather with new image
| |
| allowed: | string |
|
| Default: |
|
|
analyze |
| (only first 6 selected outputs will be displayed)
| |
| allowed: | bool |
|
| Default: | False |
|
showuv |
| display uv coverage
| |
| allowed: | bool |
|
| Default: | True |
|
showpsf |
| display synthesized (dirty) beam (ignored in single dish
simulation)
| |
| allowed: | bool |
|
| Default: | True |
|
showmodel |
| display sky model at original resolution
| |
| allowed: | bool |
|
| Default: | True |
|
showconvolved |
| display sky model convolved with output clean beam
| |
| allowed: | bool |
|
| Default: | False |
|
showclean |
| display the synthesized image
| |
| allowed: | bool |
|
| Default: | True |
|
showresidual |
| display the clean residual image (ignored in single dish
simulation)
| |
| allowed: | bool |
|
| Default: | False |
|
showdifference |
| display difference between output cleaned image and
input model sky image convolved with output clean
beam
| |
| allowed: | bool |
|
| Default: | True |
|
showfidelity |
| display fidelity (see help)
| |
| allowed: | bool |
|
| Default: | True |
|
graphics |
| display graphics at each stage to
[screen—file—both—none]
| |
| allowed: | string |
|
| Default: | both |
|
verbose |
| ||
| allowed: | bool |
|
| Default: | False |
|
overwrite |
| overwrite files starting with $project
| |
| allowed: | bool |
|
| Default: | True |
|
dryrun |
| only print information [experimental; only for
interfermetric data]
| |
| allowed: | bool |
|
| Default: | False |
|
logfile |
| ||
| allowed: | string |
|
| Default: |
|
|
void
Example
* "project" needs to be the directory of results generated by running
simobserve or simalma. In particular $project/$project.skymodel
will be required in order to compare output and input images.
-------------------------------
mode image=True:
* One should input one or more simulated MSs using the "vis" parameter.
These can include a total power MS.
Simanalyze will grid any total power MS,
clean (invert and deconvolve) any interferometric MSs,
and feather the results.
* the "vis" parameter:
- example: single MS: vis="mysim.alma.out03.ms"
- example: multiple MSs: vis="mysim.alma.out03.ms,mysim.aca.tp.ms"
- one can use "$project" and let the task automatically replace it with
the project name, e.g., vis="$project.noisy.ms,$project.noisy.sd.ms".
However, note that if you created measurement set(s) using simobserve,
MS names will include the configuration, e.g.
"$project.alma_out20.noisy.ms"
- setting "vis" to "default" will find and attempt to image
all measurement sets (interferometric and single dish) in the
project directory
* Sometimes it is preferable to grid the single dish MS using the
sdimaging task for more control. In that case one can input
the resulting single dish imaging under "featherimage", only
put interferometric MSs in "vis", and simanalyze will clean the
interferometric and feather with your "featherimage".
* Sometimes it is preferable to use a low resolution (single dish or
synthesis) image as a prior model during clean deconvolution
of a higher resolution interferometric MS. That is accomplished
by putting the low-resolution image in "modelimage" and the MS
to be deconvolved in "vis". NOTE: This is not the original skymodel
that was used in simobserve or simalma. It is recommended to
leave this blank unless the user is familiar with using a prior
in clean deconvolution. (see casaguides) NOTE 2: modelimage will
not be used if the MS to be imaged is total power.
* uses Cotton-Schwab clean for single fields and Mosaic gridding
for multiple fields (with Clark PSF calculation in minor cycles).
* interactive clean or use of more parameters than the subset
visible here are available by simply running the clean task directly,
then using simanalyze in the mode image=False (see below).
* if graphics are turned on, this step will display the clean image
and residual image
* the "mask" parameter:
Specification of cleanbox(es), mask image(s), primary beam
coverage level, and/or region(s) to be used for cleaning.
clean tends to perform better, and is less likely to diverge, if
the clean component placement is limited by a mask to where real
emission is expected to be. e.g. pixel ranges mask=[110,110,150,145],
filename of mask image mask=’myimage.mask’, or a file with mask
regions -- see help for the clean task for more information.
* NOTE: simanalyze was designed to be used after one or more runs of
simobserve, and as such it assumes it will be able to find a
sky model image called $project/$project.skymodel, .newmodel, or
.compskymodel in the $project/ subdirectory. If the simulated
MS has been created by means other than simply calling simobserve,
the user may have to copy their sky model image into the $project
subdirectory and call it "$project.skymodel"
-------------------------------
mode image=False:
* Sometimes the user has created a synthesized image themselves,
most likely using the clean task, perhaps along with
sdimaging and feather, or a previous call to simanalyze with image=True
* The user should input that simulated image as "imagename".
It will have suffix .image if created by clean, simanalyze, or simalma
* simanalyze will attempt to find an appropriate skymodel image -
this is the *.skymodel image created by simobserve or simalma,
the (optionally rescaled) original sky model, which was used
to create the measurement set.
simanalyze will look in the project directory, but if there are
multuple skymodels present it may not find the right one, so the
"skymodel" parameter allows explicit specification.
-------------------------------
mode analyze=True is used to create an image of the difference between
the input skymodel and the simulated output image (whether that output
image is being generated in the same call to simanalyze, with
image=True, or has already been generated, and simanalyze is being
called with image=False).
showuv -- display uv coverage
showpsf -- display synthesized (dirty) beam (ignored in single dish simulation)
showmodel -- display sky model at original resolution
showconvolved -- display sky model convolved with output beam
showclean -- display the synthesized image
showresidual -- display the clean residual image (ignored in single dish simulation)
showdifference -- display difference between output cleaned image and
input model sky image convolved with output clean beam
showfidelity -- display fidelity image
fidelity = abs(input) / max[ abs(input-output), 0.7*rms(output) ]
Note that the RMS is calculated in the lower quarter of the image.
This is likely not the best choice, so you are encouraged to
measure RMS yourself in an off-source region using the viewer.
dryrun=True is an advanced technical mode only useful for interferometric
(not single dish) data.
-------------------------------
Output produced: (not all will always exist, depending on input parameters)
To support different runs with different arrays, the names have the
configuration name from antennalist appended.
-------------------------------
project.[cfg].skymodel.flat.regrid.conv = input sky regridded to match
the output image, and convolved with the output clean beam
project.[cfg].image = synthesized image
project.[cfg].flux.pbcoverage = primary beam correction for mosaic image
project.[cfg].residual = residual image after cleaning
project.[cfg].clean.last = parameter file of what parameters were used in
the clean task
project.[cfg].psf = synthesized (dirty) beam calculated from weighted uv
distribution
project.[cfg].image.png = diagnostic figure of clean image and residual
project.[cfg].fidelity = fidelity image
project.[cfg].analysis.png = diagnostic figure of difference and fidelity
project.[cfg].simanalyze.last = saved input parameters for simanalyze task
-------------------------------
Please see http://casaguides.nrao.edu, and contact the CASA helpdesk
with questions.
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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