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imagepol.imagepoltestimage - Function

1.1.4 Attach the Imagepol tool to a test image file


Description

This function can be used to generate a test image and then attach the Imagepol tool to it.

The test image is 4-dimensional (RA, DEC, Stokes and Frequency). The Stokes axis holds I,Q,U and V. The source is just a constant I (if you don’t add noise all spatial pixels will be identical) and V. Q and U vary with frequency according to the specified Rotation Measure components (no attempt to handle bandwidth smearing within channels is made). The actual values of I,Q,U, and V are chosen arbitrarily otherwise (could be added as arguments if desired).

You can use this image, in particular, to explore the Rotation Measure algorithms in functions rotationmeasure and fourierrotationmeasure.

If you don’t specify the Rotation Measure, then it is chosen for you so that there is no position angle ambiguity between adjacent channels (the value will be sent to the Logger).

The noise added to the image is specified as a fraction of the total intensity (constant). Gaussian noise with a standard deviation of sigma * Imax is then added to the image.

Arguments





Inputs

outfile

Output image file name

allowed:

string

Default:

imagepol.iquv

rm

Rotation Measure (rad/m/m). Default is auto no-ambiguity determine.

allowed:

doubleArray

Default:

0.0

pa0

Position angle (degrees) at zero wavelength

allowed:

double

Default:

0.0

sigma

Fractional noise level

allowed:

double

Default:

0.01

nx

Shape of image in x direction

allowed:

int

Default:

32

ny

Shape of image in y direction

allowed:

int

Default:

32

nf

Shape of image in frequency direction

allowed:

int

Default:

32

f0

Reference frequency (Hz)

allowed:

double

Default:

1.4e9

bw

Bandwidth (Hz)

allowed:

double

Default:

128.0e6

Returns
bool

Example

 
 
"""  
#  
print "\t----\t imagepoltestimage Ex 1 \t----"  
po.imagepoltestimage(outfile=’imagepoltestimage’, rm=200)  
po.rotationmeasure(rm=’rm.out’,rmmax=250)  
ia.open(’rm.out’)  
ia.statistics()  
#viewer()  
#  
"""  
 

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