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)
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