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<< Click to Display Table of Contents >> Interferometry - Amplitude Tracking - 2 - Shift Refinement and Re-Flattening |
  
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<< Click to Display Table of Contents >> Interferometry - Amplitude Tracking - 2 - Shift Refinement and Re-Flattening |
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Purpose
This step is crucial for a correct transformation of the shifts information into displacement values. It allows to remove possible shift ramps.
The execution of this step is mandatory for Displacement Mapping in range and azimuth direction.
To execute this step a Ground Control Point file must be previously created.
Technical Note
Depending on the specific processing parameter setting (Preferences>Flattening>Refinement and Re-flattening/Refinement Method), the polynomials and the correction factors are calculated and written in the header file of the shift images (_dr/_da.sml>interferometric_processing section) - as well as on a popup window when the process is not executed in batch mode - at the process completion; these correction factors/polynomials are:
| - | RPPPhasePolyDegree - Degree of the polynomial used to estimate the phase ramp - It is generated if the "Polynomial Refinement" method is applied. |
| - | RPPPhasePoly - The polynomial used to estimate the phase ramp - It is generated if the "Polynomial Refinement" method is applied. |
| - | RPPRMSE - Root mean square error calculated as the difference between the height value of the Ground Control Points and the corresponding value in the interferometric phase (in meters) - It is generated if the "Polynomial Refinement" method is applied. |
The popup window additionally provides, for each input Ground Control Point, the following values:
| - | Mean difference between SRDEM - slant range input DEM - and SAR DEM (in meters); |
| - | Mean difference between Shift and calculated Shift Ramp (in pixels); |
| - | Standard Deviation between SRDEM and SAR DEM (meters). |
Very large "RPPRMSE" - root mean square errors - (in the order of hundreds or thousands) eventually bring to wrong results.
Ground Control Points located on null/dummy value pixels (NaN) are discarded.
The correction parameters are calculated depending on the specific "Refinement Setting" and are applied to rebuild the following input files:
| - | Shift (_dr, _da). |
| - | Synthetic Shift (_rg_sint, _az_sint). |
The points ("Refinement Ground Control Point file") used to calculate the correction parameters (Refinement Setting), shall be selected on the input shift files (_dr, _da) in order to avoid "moving areas". The Ground Control Points must be well distributed throughout the entire scene.
An indication about the Ground Control Points quality can be obtained by inspecting the "_refinement.shp" (see "Output" product description below).
Areas with good coherence should be preferred for the Ground Control Points location. In any case the importance of each GCP is weighted by the program on the basis of its coherence value.
If errors exist in the shift images, they must be corrected before running this step. Otherwise wrongly estimated areas have to be discarded for the Ground Control Points location.
Input Files
Coherence file
Name of the coherence image (_cc). This file is mandatory.
Input Range Shift File
Name of the Shift file in range direction (_dr). This file is mandatory.
Input Azimuth Shift File
Name of the Shift file in azimuth direction (_da). This file is mandatory.
Input Reference File
File name of the multi-looked Reference Intensity data (_pwr). This file is mandatory.
Input Secondary File
File name of the multi-looked coregistered Secondary Intensity data (_pwr). This file is mandatory.
Range Synthetic Shift File
Name of the synthetic shift file in range direction (_rg_sint). This file is mandatory.
Azimuth Synthetic Shift File
Name of the synthetic shift file in azimuth direction (_az_sint). This file is mandatory.
Slant Range Digital Elevation Model file
Name of the Digital Elevation Model in slant range geometry (_srdem).
Refinement GCP file
Either a previously created Ground Control Point file (.xml) is loaded (Load GCP File), or the interface to create a new Ground Control Point file is automatically loaded (Create GCP File, refer to the "Tools>Generate Ground Control Point" for details). 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
Refinement method
The choice is given between the following refinement methods:
•Automatic Refinement;
•Polynomial Refinement;
•Orbital Refinement. (Not available yet)
Refer to the flattening section of the Preferences for further information about these methods.
Refinement Residual Phase Polynomial Degree
Degree of the polynomial used to estimate the phase ramp, which will be removed from the input unwrapped phase during the Re-flattening operation. In case this value is higher that the number of input Ground Control Points, it will be automatically decreased. The default values of 3 means that a phase ramp in range and azimuth direction plus a constant phase offset will be corrected. In case only the phase offset correction is needed, the polynomial degree will be set to 1.
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 - Refinement
It brings to the flattening 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 optional.
_reflat_dr
Re-flattened interferogram in range with the associated header files (.sml, .hdr).
_reflat_da
Re-flattened interferogram in azimuth with the associated header files (.sml, .hdr).
_reflat_rg_sint
Re-flattened synthetic phase in range with the associated header files (.sml, .hdr).
_reflat_az_sint
Re-flattened synthetic phase in azimuth with the associated header files (.sml, .hdr).
_reflat_srdem
Digital Elevation Model, in slant range geometry, with the associated header files (.sml, .hdr). This file is generated only if a "Refinement Method" was selected.
_reflat.txt
Text file with the orbital correction parameters resulting from the refinement.
_refinement.shp
Shape file containing those points retained (valid GCPs) form the input "Refinement GCP file".
The following information is provided if the "Polynomial Refinement" method is applied.
| - | Unwrapped phase value (in radians) - "ReadPhase". |
| - | Absolute - "AbsPhDiff" - and relative - "PhaseDiff" - difference (in radians) between the real phase and its fitted value based on GCPs. |
| - | Standard deviation (in meters) of the input "Refinement GCP file" - "SigmaMt" - It is based on interferometric coherence and orbital configuration. |
| - | Standard deviation (in radians) of the input "Refinement GCP file" - "SigmaRad" - It is based on the interferometric coherence. |
_refinement_geo.shp
Shape file containing the geocoded location of the valid GCPs used in the refinement process.
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)
None.
Task, SARscapeBatch object, SARscapeBatch script example
References None.