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Purpose

 

This panel enables to set the default processing parameters, which are used to flatten an interferogram.

 

Technical Note

 

None.

 

Parameters - Flattening

 

Synthetic Phase Generation  

 

Optimal Resolution Approach

By setting this flag the optimal resolution interpolator (see Geocoding step) is used to generate the synthetic phase and related products.

 

DEM Resampling Factor

To set the pixel sampling of the input reference Digital Elevation Model, for the synthetic phase generation. This factor is considered for the transformation of the DEM from geocoded to slant projection. The default setting (-1) foresee two possible cases:

 

Any value other than the default setting (-1) represents the ratio factor applied to the original DEM sampling in the transformation from geocoded to slant projection. The example below refers to an original 100 m resolution DEM:

✓        2: Slant range DEM resampled to 50 m resolution

✓        3: Slant range DEM resampled to about 33 m resolution

✓        5: Slant range DEM resampled to 20 m resolution

 

Orbit Interpolation

It represents the multiplying factor, which is used to calculate the orbit position at sub pixel level in azimuth direction. The higher the value the longer the processing time and the accuracy.

 

Window Size Interpolation

This window dimension is used for the pixel interpolation of the slant range product.

 

Window Size Mean Filter

This window dimension is used for the mean filtering of the slant range product.

 

Synt Azimuth Looks

Only looks different than 0 are considered, otherwise are used the the interferometric looks for the synthetic phase generation. Only synthetic looks bigger than the interferometric looks are accepted. Values different than zero cause a software speedup during the co-registration step. These parameters are mostly intended to improve the PS interferometric step performance. Too high synthetic multilook values causes a PS product quality degradation, mostly for high resolution data, with large acquisition tube (large normal baseline and high topography sensitivity). The PS product quality degradation is almost negligible with Sentinel1 data.

 

Synt Range Looks

Only looks different than 0 are considered, otherwise are used the the interferometric looks for the synthetic phase generation. Only synthetic looks bigger than the interferometric looks are accepted. Values different than zero cause a software speedup during the co-registration step. These parameters are mostly intended to improve the PS interferometric step performance. Too high synthetic multilook values causes a PS product quality degradation, mostly for high resolution data, with large acquisition tube (large normal baseline and high topography sensitivity). The PS product quality degradation is almost negligible with Sentinel1 data.

 

 

Automatic Secondary Orbit Correction

This flag must be set, in those processes where the orbits of the Reference image are correct (i.e. the nominally geocoded image fits with the DEM) while the Secondary image orbits are not accurate (i.e. the nominally geocoded image does not fit with the DEM). By setting this flag the Secondary orbits are corrected using the Reference orbits and the coregistration shift.

 

Remove Residual Fringes        

By setting this flag the residual fringes are estimated on the wrapped phase (differential interferogram), removed from it and added to the synthetic phase (_sint). The objective is to get rid of those fringes, which remains after the removal of the phase component due to topography (i.e. DEM) and/or flat earth. This function is especially intended for those data which are affected by orbital inaccuracies. It must be noted that the original synthetic (_sint) and differential (_dint) interferograms, which are modified as result of phase removal, are saved with the prefix "original_". This parameter should be set on true only for those dataset composed by few images and where the area of interest is characterized by strong atmosphere

 

The parameters below are active only when this flag is checked.

 

Azimuth Window Size

Window Size in azimuth direction – better using power of 2 values – which is used to estimate the local fringe frequency. The window size must be larger than the orbital fringe dimension (in pixels) in order to have an optimal performance. If the window is too big, with respect to the image size, the program will automatically reduce it.

 

Range Window Size        

Window Size in range direction – better using power of 2 values – which is used to estimate the local fringe frequency. The window size must be larger than the orbital fringe dimension (in pixels) in order to have an optimal performance. If the window is too big, with respect to the image size, the program will automatically reduce it.

 

Azimuth Window Number

Number of windows, in azimuth direction, which are used for the removal process. If set to zero, the polynomial removal is not applied.

 

Range Window Number

Number of windows, in range direction, which are used for the removal process. If set to zero, the polynomial removal is not applied.

 

Polynomial Degree

The number of coefficients (from 1 to 10) used for the residual phase removal. It makes sense to have this value set at least to 2, since a dominant dependency in range is expected.

φ = K1 + K2X + K3Y + K4X2 + K5XY + K6Y2+ K7X3 + K8X2Y + K9XY2 + K10Y3

 

Low Pass Filter (m)

Window size (meters) for the Low Pass atmospheric removal, in range and azimuth direction, which is used for the removal process. If set to zero, the Low Pass removal is not applied. Suggested values are more than 15000 meters, only in case of small spatial size displacement pattern.

 

 

Refinement Method        

Different ways to perform the phase refinement (both in case of Digital Elevation Model and Displacement Map generation) are possible. One of the following methods can be selected to be used in the refinement processing step:

•Automatic: by setting this flag the orbit configuration is first evaluated based on the input Ground Control Points. If the a-priori check “Refinement Achievable RMS” is larger than the threshold, or the absolute normal baseline is smaller than the a-priori check “Refinement Minimum Baseline”, or the a-posteriori check “Refinement Final RMS” is larger than the threshold, or the a-posteriori check “Refinement RMS Ratio” is larger than the threshold, or the number of GCP is lower than 7, than the program automatically switch to the Polynomial Refinement correction method; otherwise the Orbital correction method is applied.

•Orbital: by setting this flag the orbital correction parameters are estimated using the Ground Control Points. Selecting this flag both the a-priori and the a-posteriori checks are disabled, while the only necessary condition for this method to work it is that at least 7 GCPs are available.

•Polynomial Refinement: by setting this flag a phase ramp is estimated from the unwrapped phase without considering the orbit configuration. In this case the minimum number of Ground Control Points must be equal to the “Refinement Residual Phase Poly Degree”, otherwise the poly degree is automatically decreased accordingly

By default, the Polynomial Refinement is chosen.

 

Refinement Radius (m)

Maximum buffer radius for the association of Ground Control Point with respect of the slant range unwrapped phase closer valid pixel.

 

Refinement Residual Phase Poly 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.

 

 

Refinement Achievable RMS 

A-priori check valid only when the Automatic refinement method is checked. The interferometric Signal to Noise value is considered in combination with the baseline value using the following formula:

 

((γ2/1-γ2)/2π)H

 

where γ is the interferometric coherence and H is the height of ambiguity.

The maximum acceptable height error (GCP average value expressed in meters) must be entered

 

Refinement Minimum Baseline

A-priori check valid only when the Automatic refinement method is checked. If the baseline absolute value is lower than this threshold the orbital refinement is not carried out.

 

Refinement Final RMS

A-posteriori check valid only when the Automatic refinement method is checked. Once the orbital configuration has been estimated, the real height error for each GCP can be calculated. The maximum acceptable value must be entered.

 

Refinement RMS Ratio

A-posteriori check valid only when the Automatic refinement method is checked. The maximum acceptable value of the ratio between “Refinement Final RMS” and “Refinement Achievable RMS” must be entered

 

Refinement Automatic: Slope max thr (deg)

This parameter is used by the SBAS automatic refinement procedure only. This threshold contributes to retrieve the refinement mask used instead of the manual Ground Control Points. The maximum acceptable slope value in degree must be entered

 

Refinement Automatic: Coherence min %

This parameter is used by the SBAS automatic refinement procedure only. This threshold contributes to retrieve the refinement mask used instead of the manual Ground Control Points. The percentage of pixels, among those already masked, with the highest temporal coherence value must be entered.

 

Refinement Automatic: Residual Height max %

This parameter is used by the SBAS automatic refinement procedure only. This threshold contributes to retrieve the refinement mask used instead of the manual Ground Control Points. The percentage of pixels, among those already masked, with the lower measured residual height value must be entered.

 

 

Refinement Automatic: Displacement max %

This parameter is used by the SBAS automatic refinement procedure only. This threshold contributes to retrieve the refinement mask used instead of the manual Ground Control Points. The percentage of pixels, among those already masked, with the lower measured displacement value must be entered.

 

Refinement Automatic: min Cluster Size

This parameter is used by the SBAS automatic refinement procedure only. This threshold contributes to retrieve the refinement mask used instead of the manual Ground Control Points. The minimum cluster group of pixels, in the refinement mask, acceptable size must be entered.

 

 

Refinement Automatic: MuSigma min%

This parameter is used by the SBAS automatic refinement procedure only. This threshold contributes to retrieve the refinement mask used instead of the manual Ground Control Points. The percentage of pixels, among those already masked, with the higher MuSigma (temporal Mean/Standard Deviation) value must be entered.

 

 

 

General Functions

 

Load Preferences

It allows loading specific Preferences tthirteen different settings  as possible alternative default processing values.

 

Load

It allows loading an .xml, .sml or .txt file where SARscape common Preferences where previously saved.

 

Save

It allows saving SARscape common Preferences for a future processing using the same preferences characteristics.

 

Help        

Specific help document section.

 

 

Ok        

The selected default processing parameters are loaded.

 

Cancel        

The window will be closed.

 

Specific Function(s)        

 

None.

 

References

 

None.