|
<< Click to Display Table of Contents >> Preferences specific - Persistent Scatterers |
  
|
|
<< Click to Display Table of Contents >> Preferences specific - Persistent Scatterers |
|
Purpose
This panel enables to set the default processing parameters, which are used in the Interferometric Stacking module and, in particular, within the Persistent Scatterers functionalities.
Technical Note
Multilooking
There are two different settings for the multilooking process:
-Multilooking Factor
These correspond to the factors used in between the coregistration and the generation of the interferograms. The negative "Range Looks" is because the program oversamples the input with the specified factor; the default value is mostly intended to cope with large baseline pairs.
-Multilooking Differential Interferograms
These correspond to the factors used for the generation of the differential interferograms (_dint). The values entered here are typically set to obtain approximately square pixels starting from the original single look geometry.
GCP Average Distance
The correction parameters are weighted on the basis of: i) the distance from the GCP; ii) the coherence value. The window size, which is set here in meters, has to be defined by considering the pixel sampling (ground range projected) of the input data.
Atmospheric Pattern Estimate
These parameters are used to estimate - and remove before the displacement velocities are calculated - atmospheric induced phase variations. It is done by specifying the expected scale and temporal frequency of atmospheric variation. Spatial variation in the same acquisitions are typically slow and thus a low pass filter is adopted; vice versa the changes over the time (from one to another acquisition) are much stronger and thus a high pass filter is adopted.
–Atmosphere Low Pass, this accounts for the spatial distribution of the atmospheric variations. It is implemented by using a square window: large windows are more suitable to correct large scale variations, while small windows are better to correct isolated artifacts due to localized variations. The smaller is the window size, stronger will be the filter effect.
–Atmosphere Hi Pass, this accounts for the temporal distribution of the atmospheric variations. It is implemented by using a temporal window: large windows are more suitable to correct effects with low temporal variability, while small windows are better to correct frequent atmospheric variations. The bigger is the window size, stronger will be the filter effect.
Model Solution Parameters
Depending on the displacement mechanism and dynamics it is possible to set different values for the maximum and minimum admitted residual height, which is measured respect to the reference DEM. For instance, when analysing a data set acquired over a subsidence affected area, we can set the "Min Residual Height" definitely higher than the "Max Residual Height" since the area is expected to have height values lower than those reported in the reference DEM. The opposite will happen if the area is subject to an uplift.
Parameters - Persistent Scatterers/ Enhanced - Persistent Scatterers
Baseline Threshold
This threshold corresponds to the maximum baseline value, which is considered acceptable for the PS analysis. Data pairs with baseline values outside this limit are not taken into account. This value is expressed as percentage of the critical baseline (original default is 5 times the critical value).
Number of looks in range direction.
Azimuth looks
Number of looks in azimuth direction.
Range looks for Quik View
Number of looks in range direction.
Azimuth looks for Quick View
Number of looks in azimuth direction.
PS Resampling Method
By setting the relevant flag, the interpolation method is specified.
Nearest Neighbour
Bilinear Interpolation
3rd Order Cubic Convolution
4th Order Cubic Convolution
PS Density for Statistics
Typical values, for systems like ERS, ENVISAT and RADARSAT-1, are 200 PS/sqkm in urban areas and 20 PS/sqkm in rural areas. The measurement precision (i.e. mean velocity error in mm/year) is estimated considering a number of PS/sqkm, which is equal to the value specified here. The higher this value the lower the estimated mean velocity error. Note: this is used only in the Connection Graph step for the creation of a statistic for velocity and residual heights based on the temporal/spatial baseline and the PS density value. These statistics are printed in a popup window at the end of the connection graph execution.
Product Coherence Threshold
Pixels with coherence values smaller than this threshold cannot be kept as Persistent Scatterers.
Dimension (in meters) of the window to set for the low frequency (spatial) atmospheric removal.
Area for Single Reference Point (sqkm)
Area (in square kilometers) used to define the subsets in which the dataset is divided. A single reference point is set for each zone under the area threshold.
Atmosphere High Pass Size (days)
Dimension (in days) of the window to set for the high frequency (temporal) atmospheric removal.
Area Overlap for Sub-areas (%)
For each subarea one or more pixels is/are considered as candidates (Reference Points). The analytic method to define the candidates is based on the Amplitude Dispersion Index. They are automatically analyzed for the calculation of the phase offset and just one will be selected as reference point.
Number of Candidates
Overlap Area (in percentage) between the subsets generated following the Area for Single Reference Point parameter.
pvalue
The P value is defined as the probability under the assumption of no effect or no difference (null hypothesis), of obtaining a result equal to or more extreme than what was actually observed. The P stands for probability and measures the statistical similarity of neighboring pixels located within the user defined window size.
Residual Height (Max and Min)
These correspond to the maximum (positive value) and minimum (negative value) residual height, with respect to the reference Digital Elevation Model.
Displacement Velocity (Max and Min)
This corresponds to the value expected (in mm/year) as the maximum displacement velocity.
Residual Height Sampling
This corresponds to the sampling frequency (in meters) which is used to estimate the residual height.
Displacement Sampling
This corresponds to the sampling frequency (in mm/sec) which is used to estimate the displacement velocity.
KML Max Nr of Points
If values other than -1 are entered, the output KML file is split in several parts (each marked by a progressive numbering - _01; _02; etc.); each part of the KML contains a portion of the total number of points, which corresponds to the value entered. It is suggested not to exceed 50000 points in order to avoid visualization problems.
Generate Dint Multilooked for Quick View
By setting this flag the differential interferograms, with the multilooking factors specified below, are also generated as processing outputs.
Generate Geocoded Shape Result
By setting this flag the output shape file/s are generated.
Generate Geocoded Kml Result
By setting this flag the output kml file/s are generated.
Generate Shape Time Series
By setting this flag the output shape file/s, with the displacement temporal evolution, are generated.
Generate Kml Time Series
By setting this flag the output kml file/s, with the displacement temporal evolution, are generated.
Refer Output List to Older
By setting this flag the displacements are referred to the oldest acquisition in the input file list.
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.