PSFARA

Description

Estimate Faraday rotation from fully polarimetric scattering data.

Parameters

psfara(fili, filo, flsz, angletyp)

Name	Type	Caption	Length	Value range
FILI *	str	Input fully polarimetric SAR image	1 -
FILO *	str	Output Faraday rotation angle	1 -
FLSZ *	List[int]	Filter size (pixels, lines)	1 - 2	1|3|5|7|9|11|13|15|17|19|21|23|25|27|29|31|33 Default: 5,5
ANGLETYP *	str	Angle units	1 - 7	Degrees | Radians Default: Degrees

* Required parameter

Parameter descriptions

FILI

The name of the input polarimetric SAR data set that contains the input complex polarimetric SAR data set, which must be non-symmetrized fully polarimetric (quad-polarization) complex data. The input data set must be in scattering S4c-matrix format.

The input file must be a data set that has already been imported in PCIDSK (.pix) format by SARINGEST. Alternatively, it can be the key-file name of any GDB-supported POLSAR data set in its distribution format. For more information, and a complete list of supported POLSAR sensors and data products, see SARINGEST.

FILO

The name of the output file that will hold the Faraday rotation. The file must not already exist. The output file has the same dimensions as the input SAR image, and one channel. The floating-point pixel values represent the estimated Faraday rotation angle.

FLSZ

The horizontal and vertical window size, in pixels, of the filter. The value must be an odd integer between 1 and 33. The default value is 5 x 5 pixels.

ANGLETYP

The angle units for the output channel, in degrees or radians. The default value is Degrees.

Details

Electromagnetic activity in the ionosphere can induce a path delay (Faraday rotation) that degrades the SAR signal. Faraday rotation results in range shifts and may have significant impact for some high-resolution SAR applications. PSFARA provides an estimate of the Faraday rotation (in degrees or radians) for each image pixel. The algorithm requires fully polarimetric scattering data as input and is based on the circular basis method described by Bickel and Bates in 1965.

All output angles are written in either degrees or radians, depending on the angle units setting.

Example

Calculate the filtered (5 x 5) Faraday rotation angle in degrees from a full-quad RADARSAT-2 image that has already been ingested into PCIDSK (.pix) format by SARINGEST.

from pci.psfara import psfara

fili="RSAT2_FQ.pix"
filo="RSAT2_FARADAY.pix"
flsz=[5,5]
angeltyp="Degrees"

psfara(fili, filo, flsz, angeltyp)

Algorithm

PSFARA computes the Faraday rotation angle for each pixel. The rotation angle is computed as:

Faraday = argument of the coherent average of synthesized "LR" value multiplied by Conjugate of the synthesized "RL" value /4.

References

Bickel S.H., Bates R.H.t., "Effects of Magneto-Ionic Propagation on the Polarization Scattering Matrix", Proc. IEEE, vol. 53, no. 8, pp. 1089-1091, August 1965.>

Lavalle M., Pottier E., Solimini D., Miranda N., "Faraday Rotation Estimation from Unfocussed ALOS-PALSAR Data", Presentation PolInSAR Workshop Frascati, Italy, January 2008.