PSTOUZIDEC

Description

PSTOUZIDEC performs an incoherent target-scattering decomposition in roll-invariant parameters for a fully polarimetric SAR (POLSAR) data set. It creates an image of 15 decomposition parameters. For each of the primary, secondary, and tertiary eigen vectors, the orientation angle (psi), dominant eigenvalue (lambda), Touzi alpha_s angle, Touzi phase, and helicity(tau) are computed. These parameters characterize the properties of partially coherent scattering by computing the proportion and type of the scattering mechanism for all features in your image. This information can be used further for image classification or interpretation.

Parameters

Name	Type	Caption	Length	Value range
FILI*	String	Input polarimetric SAR image	1 - 192
FILO*	String	Output Touzi decomposed raster	1 - 192
ANGLETYP	String	Angle units	0 - 7	Degrees | Radians Default: Degrees
MONITOR	String	Monitor mode	0 - 3	ON, OFF Default: ON

* 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 either non-symmetrized or symmetrized fully polarimetric (quad-polarization) complex data. The input data set must be in one of the following matrix formats: covariance, coherence, or Kennaugh. The input data set should have an equivalent number of looks (ENL) of at least 25. If the data set is single-look complex, an ENL of 25 can be achieved by applying a polarimetric filter, such as boxcar.

The input file must have already have been imported into the PCIDSK (.pix) format with SARINGEST. Input can also be the key-file name of any GDB-supported POLSAR data set in its distribution format. For more information, including a complete list of supported SAR sensors and data products, follow the link to SARINGEST at the end of this topic.

FILO

The name of the output file that will hold the polarimetric discriminators. The file name you specify must not already exist. The output file has the same dimensions as the input SAR image, and 15 channels. Their floating-point pixel values represent the proposed five Touzi-decomposition parameters: orientation angle (psi), dominant eigenvalue (lambda), Touzi alpha_s angle, Touzi phase, and helicity(tau) for the primary (channels 1-5), secondary (channels 6-10) and tertiary (channels 11-15).

ANGLETYP

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

This parameter is optional.

MONITOR

The program progress can be monitored by printing the percentage of processing completed. A system parameter, MONITOR, controls this activity.

Available options are:

• ON: Turns the monitor ON (default)
• OFF: Turns the monitor OFF (recommended if running in batch or background mode)

Details

PSTOUZIDEC performs the Touzi decomposition on a fully polarimetric (quad-pol) data set. The floating-point output represents the orientation angle (Psi), the dominant eigen value (lambda), the angle of the symmetric-scattering vector in the trihedral-dihedral basis (alpha_s), the phase difference between the vector components of the trihedral-dihedral basis (phi), and helicity (tau).

The coherency matrix is symmetrized and the HV and VH channel are combined to optimize the cross-polarization signal-to-noise ratio.

With extended natural targets, the input data should have an equivalent number of looks (ENL) of at least 25 for an unbiased decomposition parameter estimate.

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

Example

Perform a Touzi decomposition on a RADARSAT-2 data set that has already been ingested by SARINGEST. To minimize noise, the image has been filtered with PSBOXCAR.

EASI>FILI="rsat2_quadpol.pix"
EASI>FILO="rsat2_quadpol_psboxcar.pix"
EASI>FLSZ=5
EASI>run PSBOXCAR
 
EASI>FILI="rsat2_quadpol_psboxcar.pix" 
EASI>FILO="rsat2_quadpol_pstouzidec.pix"
EASI>ANGLTYP="degrees"
EASI>run PSTOUZIDEC
			

Algorithm

Like the Cloude-Pottier incoherent target-scattering decomposition, the Touzi decomposition is based on the characteristic decomposition of the coherency matrix. For reciprocal targets, the characteristic decomposition leads to the representation of the coherency matrix as the incoherent sum of three single scatterers, each weighted by its normalized and positive eigen value.

The Touzi decomposition uses the Touzi scattering-vector model to represent each coherency eigenvector in terms of unique target characteristics. Each coherency eigenvector is uniquely characterized by five independent parameters. Scattering type is described with a complex entity, whose magnitude (alpha_s) and phase (phi) characterize the magnitude and phase of target scattering.

The helicity (tau) characterizes the symmetric-asymmetric nature of target scattering. The orientation angle (psi) is the conventional Huynen tilt angle.

Target scattering can be characterized by a deep analysis of the parameters of the three eigenvectors. Touzi et al. have shown that the analysis of dominant scattering parameters can lead to efficient wetland classification [1].

References

[1] Touzi, R., "Target scattering decomposition in terms of roll invariant target parameters", IEEE TGRS, Vol. 45, No.1, pp 73-84, Jan. 2007.

[2] Touzi, R., "Speckle effect on polarimetric target scattering decomposition of SAR imagery", Canadian Journal of Remote Sensing, Vol. 33, No. 1, pp 60-68, Feb. 2007.

[3] Touzi, R., Deschamps, A. and Rother, G., "Wetland characterization using polarimetric Radarsat-2 capability", Canadian Journal of Remote Sensing, Vol. 33, No. 1, pp S56-S67, 2007.