<< Click to Display Table of Contents >> Navigation:  Help Content > Polarimetry and PolInSAR Module > Reference Guide Polarimetry > Polarimetry and PolInSAR - Polarimetry - Dual Polarimetric Entropy Alpha Anisotropy Decomposition

Purpose

 

This routine is a dual pole version of the quad pol Entropy / Alpha / decomposition. It performs an eigen-decomposition of the coherency matrix of a dual-polarimetric Single Look Complex data set. In order to facilitate the analysis of the physical information provided by the eigen decomposition of the coherency matrix, two secondary parameters are defined as a function of the eigenvalues and eigenvectors:

 

•Entropy – it is related to degree of randomness of the scattering process. It can vary from 0 to 1.

•Alpha – it relates to the type of scattering mechanism. It can vary from 0° to 90°.

 

In general the incoherent decomposition approach is suitable for discriminating the scattering of complex targets such as natural features.

 

Technical Not

The scattering matrix S  is only able to characterize, from a polarimetric point of view, coherent scatterers. On the contrary, this matrix can’t be employed to characterize distributed targets. This type of scatterers can be only characterized, statistically, due to the presence of speckle noise. Since speckle noise must be reduced, only second order polarimetric representations can be used to analyzed distributed scatterers. In the case of dual pol decomposition these second order descriptors are the 2 by 2, Hermitian average coherency matrices (J).

 

The complexity of the scattering process makes extremely difficult the physical study of a given scatter through the analysis of J. Hence, the objective of the incoherent decompositions is to separate the J matrix as the combination of the second order descriptors corresponding to simple objects, presenting an easier physical interpretation.

 

As in the case of the coherent decomposition, it is desirable that these components present some properties. First at all it is desirable that the components J correspond to pure targets in order to simplify the study. In addition the components should be independent, i.e. orthogonal. The bases in which J are not unique. Consequently different incoherent decompositions can be expressed:

 

•The Freeman Decomposition

•The Huynen Decomposition

•The Eigenvector-Eigenvalue Decomposition

 

This functionality provides the decomposition results coming from the Eigenvector-Eigenvalue method. The two single channels (i.e. entropy and alpha) coming from their linear combination are generated.

 

Note that currently the classification post processing step Polarimetic Entropy Alpha Anisotropy Classification is not available.

 

Input Files

 

Input Co-Polarization File

Input file name of the scattering matrix (_slc or _slc_list). This file is mandatory.

 

Input Cross-Polarization File

Input file name of the scattering matrix (_slc or _slc_list). This file is mandatory.

 

Parameters - Principal Parameters

 

Azimuth Window Size

Window size (in pixel) in azimuth direction. This shall be set proportionally to the multilooking factor.

 

Range Window Size

Window size (in pixel) in range direction. This shall be set proportionally to the multilooking factor.

 

Window Type

One of the following options must selected:  

 

Boxcar

A window of constant shape and size is used. (only available option)

 

Azimuth Multilook

Number of looks in azimuth.

 

Range multilook

Number of looks in range.

 

Grid Size for Suggested Looks

The grid size, in meters, used to tune range and azimuth looks. If the other parameters are manually set, the grid size will not imply a change in their values.

 

Parameters - Global

 

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

 

Parameters - Other Parameters

 

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

 

Output Files

 

Output root name

Root file name. This file is mandatory.

 

_alpha        

Alpha decomposition parameter and associated header files (.sml, .hdr).

 

 

_entropy        

Entropy decomposition parameter and associated header files (.sml, .hdr).

 

.list        

List of the decomposition parameters. It is needed for the further Entropy Alpha Anisotropy classification.

 

Details specific to the Units of Measure and Nomenclature of the output products can be found in the Data Format section.

 

General Functions

 

Exec

The processing step is executed.

 

Store Batch        

The processing step is stored in the batch list. The Batch Browser button allows to load the batch processing list.

 

Close        

The window will be closed.

 

Help

Specific help document section.

 

 

Specific Function(s)

 

The most appropriate range and azimuth multi-looking factors are calculated. This calculation is performed by taking into account the Cartographic Grid Size, which is set in the relevant SARscape Default Values panel.

 

See Also

 

Task, SARscapeBatch object, SARscapeBatch script example

 

References

 

ESA, Polarimetric SAR Interferometry tutorial

 

Cloude, S.R. and E. Pottier: "A review of target decomposition theorems in radar polarimetry". IEEE Trans. GRS, vol. 34(2), pp. 498-518, Mar. 1996.

 

Cloude, S.R. and E. Pottier: "Symmetry, zero correlations and target decomposition theorems". Proc. 3rd Int. Workshop on Radar Polarimetry (JIPR ’95), IRESTE, University of Nantes, Mar. 1995, pp. 58–68.

 

S. R. Cloude: "An entropy based classification scheme for polarimetric SAR data". Proc. IGARSS’95, Florence, Italy, July 1995, pp. 2000–2002.

 

Cloude, S.R.: “The dual polarisation entropy/alpha decomposition: a palsar case study”, Polinsar 2007