Getting Started

Documentation

Glish

Learn More

Programming

Contact Us

Version 1.9 Build 1488

News	FAQ
Search	Home

imagepoltestimage - Constructor

	Package	general
	Module	images
	Tool	imagepol

Create an Imagepol tool and a test image file

Synopsis
imagepoltestimage(outfile, rm, pa0, sigma, nx, ny, nf, f0, bw)

Arguments

outfile	in	Output image file name
		Allowed:	String
		Default:	imagepol.iquv
rm	in	Rotation Measure (rad/m/m)
		Allowed:	Vector of float
		Default:	Auto no-ambiguity determine
pa0	in	Position angle (degrees) at zero wavelength
		Allowed:	Float
		Default:	0
sigma	in	Fractional noise level
		Allowed:	Float
		Default:	0.001
nx	in	Shape of image in x direction
		Allowed:	Integer
		Default:	32
ny	in	Shape of image in y direction
		Allowed:	Integer
		Default:	32
nf	in	Shape of image in frequency direction
		Allowed:	Integer
		Default:	32
f0	in	Reference frequency (Hz)
		Allowed:	Float
		Default:	1.4e9
bw	in	Bandwidth (Hz)
		Allowed:	Float
		Default:	128e6

Returns
Imagepol tool or fail

Description

The constructor can be used to generate a test image and then create an Imagepol tool from 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 * I_max is then added to the image.

Example

- p1 := imagepoltestimage(rm=200)
- p1.rotationmeasure(rm='rm.out', rmmax=250)
- rm := image('rm.out')
- rm.view()