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imagepol.sigmalinpolposang - Function

	Package	general
	Module	images
	Tool	imagepol

Error in linearly polarized position angle

Synopsis
sigmalinpolposang(clip, sigma, outfile)

Arguments

clip	in	Clip level for auto-sigma determination
		Allowed:	Float
		Default:	10
sigma	in	Standard deviation of thermal noise
		Allowed:	Float
		Default:	Auto determined
outfile	in	Output image file name
		Allowed:	String
		Default:	Unset

Returns
Image tool or fail

Description

This function (short-hand name slppa) returns the error (standard deviation) of the linearly polarized position angle ( 0.5tan^-1(U/Q) $\sqrt{(Q^2+U^2)}$) in degrees. This result comes from standard propagation of errors. The result is an Image tool as the error is signal-to-noise ratio dependent.

This function requires the standard deviation of the thermal noise. You can either supply it if you know it, or it will be worked out for you with outliers from the mean clipped at the specified level.

Example

- p := imagepol('stokes.cube')
- siglppa := p.sigmalinpolposang()