Gamma LAT: Reference Manual

polcovar

ANSI-C program: polcovar.c

NAME
polcovar - Calculate polarimetric covariance matrix C elements from HH, HV, and VV SLC data

SYNOPSIS
polcovar <SLC-1> <SLC-2> <SLC-3> <SLC1_par> <SLC2_par> <SLC3_par> <C> <C_par> <rlks> <azlks> [loff] [nlines]

<SLC-1>	(input) HH single-look complex image (scomplex or fcomplex format)
<SLC-2>	(input) HV single-look complex image (scomplex or fcomplex format)
<SLC-3>	(input) VV single-look complex image coregistered with SLC-1 (scomplex or fcomplex format)
<SLC1_par>	(input) HH SLC image parameter file
<SLC2_par>	(input) HV SLC image parameter file of SLC-2 coregistered with SLC-1
<SLC3_par>	(input) VV SLC image parameter file of SLC-3 coregistered with SLC-1
<C>	(output) root file name of covariance matrix elements (e.g. scene_id): .c11, .c22, .c33 (float), .c12, .c13, .c23 (fcomplex)
<C_par>	(output) MLI image parameter file associated with the covariance matrix element data files
<rlks>	number of range looks for the averaging window
<azlks>	number of azimuth looks for the averaging window
[loff]	offset to starting line (default: 0)
[nlines]	number of SLC lines to process (enter - for default: entire file)

EXAMPLE

polcovar slc/20080409_HH.slc slc/20080409_HV.slc slc/20080409_VV.slc slc/20080409_HH.slc.par slc/20080409_HV.slc.par slc/20080409_VV.slc.par COV/20080409_HH_HV_VV COV/20080409_HH_HV_VV.cov_mli.par 3 6

This calculates the elements of the polarimetric covariance matrix c11, c22, c33, c12, c13, c23 and stores them in the files with the root file name COV/20080409_HH_HV_VV and ending in .c11, .c22, .c33, .c12, .c13, .c23.

DESCRIPTION

The 3x3 covariance matrix [1] contains information on the averaged polarimetric signature of the illuminated scene and is the basis for further polarimetric filtering and classification.
For monostatic radar data the covariance matrix elements are calculated from the HH, HV, and VV SLC data by spatial averaging of products and averaging spatially. For each point the feature vector F contains the values of the complex scattering HH, HV, and VV, where HH is the scattering with transmit H receive H, HV is transmit H, receive V, and VV is transmit V and receive V. Essentially all natural scatterers exhibit reciprocity such that HV = VH for monostatic scattering. With this assumption, a feature vector with 3 elements is sufficient to characterize the radar backscatter polarimetric signature:

The 3x3 covariance matrix C is given by:

C = <F · F^*T>

The <> operator denotes a spatial averaging over the window with dimensions rlks in range and azlks in azimuth.

the coefficients on the diagonal C11, C22, and C33 are real-valued and are proportional to the power in the each of the 3 channels. The off-diagonal elements are complex-valued and contain the information on the relative phase between the channels. The span is defined as the sum of the diagonal matrix elements of the C matrix and has the same value as the span of the coherence matrix T calculated by polcoh. By construction, the covariance matrix is Hermetian.

[1] Lee, J. S., Eric Pottier, "Polarimetric Radar Imaging: from Basics to Applications," Chapter 3, CRC Press, Boca Raton, 2008

SEE ALSO
polcoh, pauli