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<< Click to Display Table of Contents >> Polarimetry and PolInSAR - Polarimetric Interferometry - Coherence Optimisation |
  
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<< Click to Display Table of Contents >> Polarimetry and PolInSAR - Polarimetric Interferometry - Coherence Optimisation |
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Purpose
The main scattering mechanisms, of a full polarimetric linearly-polarized Single Look Complex (SLC) acquisition pair, are estimated. It is performed by identifying those mechanisms that correspond to the highest value of interferometric coherence. The corresponding interferograms and coherence data are provided as result.
The data must have been previously coregistered.
Technical Note
The dependency of the interferometric coherence from the polarization of the images used to form the interferogram leads to consider the question of which polarization yields the highest coherence. In essence, the problem is to optimize the general formulation of the interferometric coherence, i.e.
After tedious algebra, it can be demonstrated that the maximum possible coherence value gopt1, which can be obtained by varying the polarization, is given by the square root of the maximum eigenvalue. Each eigenvalue is related to a pair of eigenvectors (w1i,w2i): one for each image. The first vector pair (w11,w21) represents the optimal polarizations. The second and third pairs (w12,w22) and (w13,w23), belonging to the second and third highest singular values, represent optimal solutions in different polarimetric subspaces.
These three optimal complex coherence data can be obtained directly by using the estimated eigenvalues:
It is important to note that the pixel sampling of the input master/slave data and synthetic phase, must be the same.
If the Range Looks and the Azimuth Looks are set to 1, the output products are over sampled (i.e. multiplied by a factor two) in range direction.
Input Files
Master HH file
Input file name of the master polarimetric HH data (_slc). This file is mandatory.
Master HV file
Input file name of the master polarimetric HV data (_slc). This file is mandatory.
Master VH file
Input file name of the master polarimetric VH data (_slc). This file is mandatory.
Master VV file
Input file name of the master polarimetric VV data (_slc). This file is mandatory.
Slave HH file
Input file names of the slave polarimetric HH data set (_slc). This file is mandatory.
Slave HV file
Input file names of the slave polarimetric HV data (_slc). This file is mandatory.
Slave VH file
Input file names of the slave polarimetric VH data (_slc). This file is mandatory.
Slave VV file
Input file names of the slave polarimetric VV data (_slc). This file is mandatory.
DEM/Cartographic System
Digital Elevation Model file
Name of the Digital Elevation Model file. This should be referred to the ellipsoid.
Output Projection
In case that the Digital Elevation Model is not used, the following parameters are compulsory to define the Cartographic System:
State
Definition of the country or general projection systems.
Projection
Definition of the projection system of the selected State. In case that a general projection system is selected in State, the Projection is automatically set.
Ellipsoid
Definition of the ellipsoid. This is chosen according to the selected State and Projection.
Hemisphere
Definition of the hemisphere. This is chosen according to the selected State and Projection.
Zone
Definition of the zone. This is chosen according to the selected State and Projection.
Datum Shift Parameters
Definition of the datum shift parameters. These are chosen according to the selected State and Projection.
Reference Height
In case that the Digital Elevation Model is not used, a constant ellipsoidal height must be provided. Default Reference Height is 0.
Cartographic Parameters
The reference parameters for some projection systems (e.g. Stereographic, Polar Stereographic, Gnomonic, Mercator, Miller, Albers, etc.) can be set.
Parameters - Principal Parameters
Filter Dimensions
The size (in pixels) of the window used during the coherence estimation and maximization process. It shall be set proportionally to the multilooking factors. Note that, in case of "Adaptive Window" type, it corresponds to the maximum window size:
Azimuth Size
Window dimension in azimuth direction.
Range Size
Window dimension in azimuth direction.
Filter Type
The estimation of the coherence and the maximization process can be performed by using:
Boxcar Window
A box-car window of fixed size for the whole image.
Adaptive Window
A window of variable size and shape, which is estimated depending of the local stationarity of the signal Intensity.
Azimuth Looks
Number of looks in azimuth.
Range Looks
Number of looks in range.
Remember that, in case the multilooking factor is manually calculated (i.e. without using the "Looks" button), the input coregistered data are over sampled two times in range direction, thus the range multilooking factor must be doubled with respect to that calculated for the original (i.e. not coregistered) data.
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.
Coregistration with DEM
By setting this flag, the input Digital Elevation Model is used in the coregistration process.
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 - Flattening
It brings to the flattening section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.
Parameters - Coregistration
It brings to the coregistration 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
Name of the output file. This file is mandatory.
_max_cc
Maximum estimated coherence with the associated header files (.sml, .hdr).
_max_dint
Interferogram relevant to the maximum estimated coherence with the associated header files (.sml, .hdr).
_med_cc
Medium estimated coherence with the associated header files (.sml, .hdr).
_med_dint
Interferogram relevant to the medium estimated coherence with the associated header files (.sml, .hdr).
_min_cc
Minimum estimated coherence with the associated header files (.sml, .hdr).
_min_dint
Interferogram relevant to the minimum estimated coherence with the associated header files (.sml, .hdr).
_ml_sint
Multilooked synthetic phase with the associated header files (.sml, .hdr).
_ml_srdem
Multilooked slant range Digital Elevation Model with the associated header files (.sml, .hdr). This file is generated only if the original product (i.e. rootname_srdem) is available in the input folder.
_parameter_polarimetric_coh_opt
Parameters set.
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)
| Looks |
The most appropriate range and azimuth multi-looking factors are calculated. This calculation takes into account of the over sampling in the input coregistered data.
Task, SARscapeBatch object, SARscapeBatch script example
References ESA, Polarimetric SAR Interferometry tutorial S. Cloude and K. Papathanassiou: "Polarimetric SAR interferometry". Geoscience and Remote Sensing, IEEE Transactions on, vol. 36, no. 5, Part 1, Sept. 1998, pp. 1551 - 1565. A. Monti Guarnieri et al.: "Multi-mode ENVISAT ASAR interferometry: techniques and preliminary results". Radar, Sonar and Navigation, IEE Proceedings -, vol. 150, no. 3, 2 June 2003, pp. 193 - 200. J. Lee et al.: "Speckle filtering and coherence estimation of polarimetric SAR interferometry data for forest applications" Geoscience and Remote Sensing, IEEE Transactions on, vol. 41, no. 10, Part 1, Oct. 2003, pp. 2254 - 2263. G. Vasile et al.: "Intensity-driven adaptive-neighborhood technique for polarimetric and interferometric SAR parameters estimation". Geoscience and Remote Sensing, IEEE Transactions on, vol. 44, no. 6, June 2006, pp. 1609 - 1621.