ANSI-C program: stokes_qm.c
NAME
stokes_qm - Calculate quantitative measures derived from Stokes
parameters (e.g. degree of polarization)
SYNOPSIS
stokes_qm <S> <S_par> [m] [s2chi] [s2psi]
[m_l] [m_c] [lp_ratio] [cp_ratio] [mu] [rphase] [alpha]
[phi]
| <S> | (input) root file name of 4 Stokes parameter files with extensions .s0, .s1, .s2, .s3 (float) |
| <S_par> | (input) image parameter file associated with the Stokes parameter data files (enter - for none) |
| <m> | (output) degree of polarization: sqrt(s1**2 + s2**2 + s3**2)/s0 (enter - for none) (float) |
| <s2chi> | (output) sine of the latitude of the Stokes vector on the Poincare sphere: sin(2*chi) = -s3/(m*s0) |
| <s2psi> | (output) sine of the longitude of the Stokes vector on the Poincare sphere: sin(2*psi) = s2/sqrt(s1**2 + s2**2)) |
| <m_l> | (output) degree of linear polarization: sqrt(s1**2 + s2**2)/s0 (enter - for none) (float) |
| <m_c> | (output) degree of circular polarization: s3/s0 (enter - for none) (float) |
| <lp_ratio> | (output) linear polarization ratio: (s0 - s1)/(s0 + s1) 0 <= lp_ratio (enter - for none) (float) |
| <cp_ratio> | (output) circular polarization ratio: (s0 - s3)/(s0 + s3) 0 <= cp_ratio (enter - for none) (float) |
| <mu> | (output) coherency parameter |mu|: sqrt(s2**2 + s3**2)/sqrt(s0**2 - s1**2) (enter - for none) (float) |
| <delta> | (output) relative H and V phase difference atan(s3/s2) (enter - for none) (radians, float) |
| <alpha> | (output) alpha parameter in the compact H/alpha decomposition: 0.5*atan(sqrt(s1**2 + s2**2)/s3) (enter - for none)(radians, float) |
| <phi> |
(output) longitude of Stokes vector 2*psi:
atan(s2/s1) (enter - for none) (radians, float) |
EXAMPLE
stokes_qm 20080409_HH_HV 20080409_HH_HV.mli.par m s2chi
s2psi m_l m_c lp_ratio cp_ratio mu delta alpha phi
generates the different measures derived from the Stokes
vectors files: 20080409_HH_HV.s0, 20080409_HH_HV.s1,
20080409_HH_HV.s2, 20080409_HH_HV.s3
DESCRIPTION
This program takes as input the Stokes parameters calculated with the program stokes and calculates a number of parameters the characterize the measured field. The total incident field can be decomposed into the sum of polarized and an unpolarized components. The four Stokes parameters describe the both the unpolarized and polarized components. The first parameter S0 is total power of the field and is the sum of each of the orthogonal polarization channels, for example the H and V receiver channels. The other 3 Stokes parameters measure the difference in power for 3 orthogonal polarization basis: H and V, 45 and -45 degrees linear, and RCP/LCP circular.
The degree of polarization of the field denoted m is the ratio between the power in the polarized component and the total power:
m = (S12 + S22 + S32)1/2 / S0
where (S12 + S22 + S32)1/2 is the power of the polarized components of the field.
Other values derived from the Stokes parameters are calculated including, degree of circularity, degree of linearity, sine of the latitude and longitude of the polarized component of the Stokes vector on the Poincare sphere, coherency parameter, phase difference between the H and V channels, scattering parameter alpha, and phase angle defined by atan(s2/s1) as described in references [1], [2], [3]. These parameters are used in calculation of various polarimetric decompositions for compact polarimetry including the m-chi, m-alpha, and m-delta decompositions.
[1] Raney, R. K., "Dual-Polarized SAR and Stokes Parameters,", IEEE Geoscience and Remote Sensing Letters, Vol. 3, no. 3. pp. 317-319, July 2006.
[2] Raney, R. K. et al. "The Lunar Mini-RF Radars: Hybrid Polarimetric Architecture and Initial Results," Proceedings of the IEEE, Vol. 99, no.5, pp 808-823, May, 2011.
[3] Cloude, S. R, et al.m "Compact Decomposition Theory," IEEE Geoscience and Remote Sensing Letters, Vol. 9, no. 1. pp. 28-32, January 2012.
SEE ALSO
typedef_ISP.h, stokes, m-chi,
m-alpha, m-delta