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dish.imagems - Function



Package dish
Module dish
Tool dish


Make an image from all scans in a MeasurementSet.


Synopsis
imagems(msname, start, stop, step, imname, spwid, nx, ny, cellx, celly, gridfn, convsupport)


Description
This command is a more general facility than its complement makeim. Where makeim will operate only on the scans for a given procedure, imagems will operate on all the scans found within a MeasurementSet; this is particularly useful for creating a data cube from several mapping procedures around the same region. Like makeim, it will construct a data cube (position-position-frequency). It uses the imager tool to achieve this. The user selects the MeasurementSet into which all of the mapping scans have been filled, specifying the channel range over which to produce the cube (start, stop). An optional averaging is offered through the step argument. The cell size can also be optionally specified with the number and units; both cellx and celly must be specified to over-ride the default calculated value (e.g., cellx='4arcmin',celly='4arcmin'). The default gridding function is the boxcar (BOX); PB (primary beam) and SF (prolate spheroidal) may also be specified. For the BOX and SF gridding functions, the size of function can be specified through the convsupport argument. The units of convsupport are pixels in the resulting image and this specifies a radial size of the convolving function. For BOX, a convsupport of 0 (the default) corresponds to nearest cell gridding. A convsupport of 1 is boxcar of width 3 (-1, 0, and +1). For SF gridding, the default size is 1 a radius of 1 pixel. Larger values may produce images with better noise characteristics at the expense of a loss of spatial resolution. There is no gridding along the frequency axis (data are mearly averaged into the nearest frequency channel as they are gridded on to the image). The default value is chosen when convsupport has a boolean or non-numeric value.



Arguments

msname   MeasurementSet name
    Allowed: string
    Default: no default
start   starting channel
    Allowed: integer
    Default: no default
stop   stopping channel
    Allowed: integer
    Default: no default
step   number of channels to average over for final cube
    Allowed: integer
    Default: 1
imname   name of output image
    Allowed: string
    Default: scanimage
spwid   spectral window id number
    Allowed: integer
    Default: F
nx   number of cells in x
    Allowed: integer
    Default: F
ny   number of cells in y
    Allowed: integer
    Default: F
cellx   cell size in x
    Allowed: string
    Default: F
celly   cell size in y
    Allowed: string
    Default: F
gridfn   gridfunction to use; BOX, PB or SF
    Allowed: string
    Default: BOX
convsupport   convolution support radius for BOX or SF
    Allowed: integer
    Default: F


Returns
T (if successful)


Example
- d.imagems('cloud_SP',520,1000,imname='cloud.im');





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