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<< Click to Display Table of Contents >> Preferences specific - Flattening |
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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.
Digital Elevation Model 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:
| - | Optimal Resolution Approach: a slant range DEM with pixel sampling equal to 2 times the SAR image ground range resolution is used; in case the DEM original resolution is better than the SAR image ground range resolution, this last one will be used. |
| - | Optimal Resolution Approach not flagged: a slant range DEM with pixel sampling equal to half the SAR image ground range resolution is used; in case the DEM original resolution is better than half the SAR image ground range resolution, the original DEM sampling will be used. |
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.
Automatic Slave Orbit Correction
This flag must be set, in those processes where the orbits of the master image are correct (i.e. the nominally geocoded image fits with the DEM) while the slave image orbits are not accurate (i.e. the nominally geocoded image does not fit with the DEM). By setting this flag the slave orbits are corrected using the master orbits and the coregistration shift.
Remove Residual Phase Frequency
By setting this flag the residual phase frequency is 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_".
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 and Re-flattening" processing step:
| - | Automatic: by setting this flag the orbit configuration is first estimated on the basis of the input Ground Control Points. If the "A-priori check>Achievable RMS" is larger than the threshold, or the absolute normal baseline is smaller than the "A-priori check>Minimum Baseline", or the "A-posteriori check>Final RMS" is larger than the threshold, or the "A-posteriori check>RMS Ratio" is larger than the threshold, or the number of GCP is lower than 7, than the program automatically switch to the "Residual Phase" 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 has to be equal to the "Residual Phase Poly Degree", otherwise the poly degree is automatically decreased accordingly. |
By default, the Polynomial Refinement is chosen.
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.
A-priori check (active only when the "Default" refinement method is checked)
| - | Achievable RMS: 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.
| - | Minimum Baseline: If the baseline absolute value is lower than this threshold the orbital refinement is not carried out. |
A-posteriori check (active only when the "Default" refinement method is checked)
| - | Final RMS: once the orbital configuration has been estimated, the real height error for each GCP can be calculated. The maximum acceptable value must be entered. |
| - | RMS Ratio: the maximum acceptable value of the ratio between "Final RMS" and "Achievable RMS" 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.