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<< Click to Display Table of Contents >> Polarimetry and PolInSAR - Polarimetric Interferometry - Polarimetric Interferogram Generation |
  
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<< Click to Display Table of Contents >> Polarimetry and PolInSAR - Polarimetric Interferometry - Polarimetric Interferogram Generation |
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Purpose
An interferogram can be generated using the same polarization of the polarimetric interferometric acquisition pair. It must be noted that, for the interferogram generation, Reference and Secondary data must have been previously coregistered. If the synthetic phase is entered as input, then the topography is removed and the output file will be a flattened interferogram.
Technical Note
For each resolution element two coregistered scattering matrices are available. The complete information measured by the SAR system can be represented in form of three 3 by 3 complex matrices T11, T22, and Ω12 formed formed using the outer products of the scattering vectors k1 and k2 as:
T11 = kT1. k1 T22 = kT2 . k2 Ω12 = kT1 . k2
T11 and T22 are the conventional polarimetric coherency matrices which describe the polarimetric properties for each individual image separately, and Ω12 is a complex matrix containing polarimetric and interferometric information. The two complex scalar images (i1 and i2) forming the interferogram are obtained by projecting the scattering vectors (k1 and k2) onto two unitary complex vectors w1 and w2, which define the polarization of the two images respectively as:
i1 = wT1 . k1 and i2 = wT2 . k2
The interferogram related to the polarizations given by w1 and w2 is then:
i1 i*2 = (wT1 . k1) (wT2 . k2)T
Two cases should be distinguished:
•w1 is equal to w2, i.e. images with the same polarization are used to form an interferogram. In this case the interferometric phase contains only the interferometric contribution due to to the topography and range variation, while the interferometric coherence expresses the interferometric correlation behaviour.
•w1 is not equal w2 , i.e. images with different polarization are used to form the interferogram. In this case the interferometric phase contains, besides the interferometric component, also the phase difference between the two polarizations. The interferometric coherence expresses, apart from the interferometric correlation behaviour, also the polarimetric correlation between Reference and Secondary:
| γ (w1, w2) = γInt . γ2 |
It is important to note that, when using the synthetic phase as input, its pixel sampling must be the same of the input Reference/Secondary data. Note that in this module only the first case is considered. If one wishes to use images with different polarization (the second case), the Polarimetric Features module's Polarimetric Phase Difference (PPD), should be used.
If the Range Looks and the Azimuth Looks are set to 1, the output products are generated with the same multilooking factors as the input data. . It is important to know that, unlike the multi-looked intensity images generated in the "Basic module>Multilooking", these Reference and Secondary intensities cannot be radiometrically calibrated due to the spatial varying effect introduced by the spectral shift filter.
Input Files
Input Reference file
File name of the Reference data (slc_rsp, _slc_list_rsp). This file is mandatory.
Input Secondary file
File name of the Secondary data (slc_rsp, _slc_list_rsp). This file is mandatory.
DEM/Cartographic System
Digital Elevation Model file
Digital Elevation Model file name. This should be referred to the ellipsoid. In case a list of input files is entered, the DEM must cover the whole imaged area. This file is optional.
Output Projection
In case that the Digital Elevation Model is not used, it is mandatory to define the Cartographic System.
To use the same coordinate system as another dataset, click the Import from Existing Dataset button and select the source dataset.
To apply the same Coordinate System of the current selected layer
The reset icon allows to reset the coordinate system field.
Parameters - Principal Parameters
Azimuth Multilooks
Number of looks in azimuth.
Range Multilooks
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.
Coregistration With DEM
This parameter can not be defined by the user.
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 root. This file is mandatory.
_int
Interferogram with the associated header files (.sml, .hdr).
_dint
Flattened interferogram with the associated header files (.sml, .hdr). This file is generated only if the input synthetic phase is entered.
_pwr
Multi-looked Reference and Secondary image with the associated header files (.sml, .hdr).
_orb.sml
Xml file containing the scene orbital parameters.
_cc
Estimated coherence with the associated header files (.sml, .hdr). This file is generated only if the Coherence Generation flag is selected.
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.
Task, SARscapeBatch object, SARscapeBatch script example
References ESA, Polarimetric SAR Interferometry tutorial