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| <pre>
| | {{imhead}} |
| Help on imhead task:
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| List, get and put image header parameters
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| This task allows the user to manipulate some meta-data parameters in an
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| image. The mode='list' shows those keywords that are
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| presently implemented, with their values. The contents associated
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| with the keywords can be obtained (get) and changed (put).
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| Additional image parameter listings are available.
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| [For visibility files, the taskname='vishead' should be used.]
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| The modes that are available are:
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| list --- Lists the image header keywords and values.
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| Use this if 'get' and 'put' are executed.
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| get --- Get the specified keyword value(s) from the image
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| put --- Put the specified keyword value(s) into the image
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| history --- Display the history information in hte CASA logger.
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| summary --- Information summarizing the CASA image file.
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| fits --- Lists the header information in a FITS style (not available)
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| add --- Adds a new header key. Use with caution
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| del --- Delete a header key, hdkey. Use with caution
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| Parameters currently implemented are listed using mode = 'list'
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| beammaj Major axis of the clean beam
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| beammin Minor axis of the clean beam
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| beampa Position angle of the clean beam
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| bunit Image pixel units (K, Jy/beam, etc)
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| cdeltn Pixel size, nth axis (max n is 4)
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| crpixn Pixel coordinate of reference point, nth axis
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| crvaln Pixel location of reference point, nth axis
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| ctypen Axis name, nth axis
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| cunitn Pixel units, nth axis
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| datamax Maximum pixel value in image
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| datamin Minimum pixel value in image
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| date-obs Date of the observation
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| equinox Reference frame for directional coordinates
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| imtype Image type: intensity,
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| minpos
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| minpixpos
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| maxpos
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| maxpixpos
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| object Source name
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| observer Observer name
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| projection Image projection ('SIN','TAN', or 'ZEA')
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| reffreqtype Reference frame for the spectral coordinates
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| restfrequency Rest Frequency
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| telescope Telescope name
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| Keyword arguments:
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| imagename --- Name of input image
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| default: none; example: imagename='ngc5921_task.image'
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| mode --- Mode: options:
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| default: none; 'list', 'summary', 'fits', 'history',
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| 'get', 'put', 'add', and 'del'
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| NOTE: 'add' and 'del' should be used with caution
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| hdkey --- keyword to use with get, put, add, or del
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| default: none; example: hdkey='telescope'
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| hdvalue --- keyword value that is 'got', or to be 'put' or
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| to be 'added'
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| default: ''; example: hdvalue='VLA'
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| Examples:
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| hdkey='date-obs';hdvalue='2007/06/20/00:00:00'
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| hdkey='beammajor';hdvalue='55arcsec'
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| hdkey='beampa'';hdvalue='0deg'
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| hdkey='restfrequency';hdvalue='1.421GHz'
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| hdkey='restfrequency';hdvalue='1.421GHz, 115.272GHz'
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| hdkey='projection';hdvalue='TAN'
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| hdkey='cdelt4';hdvalue=24415.05
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| hdkey='cdelt1';hdvalue='7.75e-5deg'
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| hdkey='crval1';hdvalue=qa.quantity( '763180', 'arsec')
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| hdkey='crval1';hdvalue='14:07:58'
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| hdkey='crval4';hdvalue='6250000Hz'
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| hdtype --- Used only with 'add' mode. It is the data type that
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| is used to store the hdkey. It can not be used to
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| change the data type of an exiting keyword.
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| options: bool, int, string, doubple, complex
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| default: none; example hdtype='double'
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| Note that hdvalue will contain numbers, strings as well as units.
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|
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| Examples:
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| 1) get the clean beam from one image and put it in a second image
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| options: bool, int, string, doubple, complex
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| default: none; example hdtype='double'
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| Note that hdvalue will contain numbers, strings as well as units.
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| Examples:
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| 1) get the clean beam from one image and put it in a second image
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| Get the clean beam from image1 into hdvalue
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| imagename = 'image1.im'; mode = 'get'; hdkey = 'beam'
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| hdvalue = imhead()
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| print hdvalue # to see values
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| To then put the clean beam into image2
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| imagename = 'image2.im', mode = 'put'; imhead()
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| 2) Most output values are dictionaries:
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| mode = 'get'; hdkey = 'maxpos'; aa = imhead()
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| would give for the command print aa
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| {'value': '03:19:48.160, +41.30.42.103, I, 4.88163e+09Hz', 'unit': ''}
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| print aa['value'] gives
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| 03:19:48.160, +41.30.42.103, I, 4.88163e+09Hz
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| print aa['value'[1][0:12] gives 03:19:48.160
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| mode = 'get'; hdkey = 'crpix1'; aa = imhead()
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| would give for the command print aa
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| {'value': '128.0', 'unit': ''}
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| print aa['value'] gives
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| 128.0 (a string)
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| 3) The use of put is a bit more straight-forward
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| mode = 'put'; hdkey = 'crpix1'; hdvalue = '200'; imhead()
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| then
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| mode = 'get'; hdkey = 'crpix1'; aa = imhead() would give
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| {'value': '200.0', 'unit': ''}
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| </pre>
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