Help Content > Interferometric Stacking > Persistent Scatterers > 2

Purpose

This functionality enables to execute, in an automatic way, the following processing sequence:

–Interferogram Generation and Flattening.

This step is mandatory.

Technical Note

The different steps implemented here are executed using the default processing approach (consult the reference guide specific to each processing step for more details); in particular:

•During the coregistration step, all sampled images are coregistered onto the resampled " Master file" . This involves an oversampling of a factor 4, in range direction (refer to the Preferences>Persistent Scatterers>Range Looks setting), which is executed to avoid aliasing of fast fringes in case of large baseline values. Differently from the standard InSAR processing, since the PS approach is looking at point targets, the spectral shift and the common Doppler bandwidth filters are not executed.The interferograms are then generated for each slave (i.e. "Input File List") using always the same master image (i.e. "Reference file").

•The Interferogram Flattening is performed using an input reference Digital Elevation Model or the ellipsoidal model if the DEM is not inputted; the "Geometry GCP file", if entered, is used to correct the master image (i.e. Super Master acquisition of the interferometric stack) onto the Digital Elevation Model. The better the reference Digital Elevation Model accuracy/resolution the better the result in terms of topography removal. It is important to note that, in case the Super Master image has already been corrected with the manual or the automatic procedure the GCP is not needed.

The data multilooking factors are relevant to the Master image. In case the input SAR series contains data with different pixel sampling (e.g. ALOS PALSAR FBS and FBD acquisitions), the program automatically changes the multilooking factors of each interferometric pair depending on its master acquisition mode.

Due to the large number of output products, the following three meta files are generated. They enable to load at once all relevant output products:

•slant_dint_meta, which refers to all flattened interferograms.

•slant_pwr_meta, which refers to all slant range power images.

In order to avoid loading failures it is recommended not to move any file from its original repository folder.

Input Files

Auxiliary file

Reference file generated as output of the "Connection Graph" step and possibly updated afterwards. This file is mandatory.

Optional Files

Geometry 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 optional. This file is optional.

DEM/Cartographic System

Digital Elevation Model file

Name of the Digital Elevation Model file. This should be referred to the ellipsoid. This file is optional. In case it is omitted, the ellipsoidal height and the relevant cartographic reference system, must be entered.

Output Projection

In case that the Digital Elevation Model is not used, the following parameters are compulsory to define the Cartographic System:

State

Definition of the country or general projection systems.

Projection

Definition of the projection system of the selected State. In case that a general projection system is selected in State, the Projection is automatically set.

Ellipsoid

Definition of the ellipsoid. This is chosen according to the selected State and Projection.

Hemisphere

Definition of the hemisphere. This is chosen according to the selected State and Projection.

Zone

Definition of the zone. This is chosen according to the selected State and Projection.

Datum Shift Parameters

Definition of the datum shift parameters. These are chosen according to the selected State and Projection.

Reference Height

In case that the Digital Elevation Model is not used, a constant ellipsoidal height must be provided. Default Reference Height is 0.

Parameters - Principal Parameters

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. These generated files only have visualization purposes and are not used for processing.

Range looks for Quick View

Number of looks in range direction (this field is active only if "Generate Dint Multilooked for Quick View" is set to TRUE). Note: Looks factor is not automatically detected.

Azimuth looks for Quick View

Number of looks in azimuth direction (this field is active only if "Generate Dint Multilooked for Quick View" is set to TRUE). Note: Looks factor is not automatically detected.

Rebuild All

By setting this flag the whole process is started from scratch.

It is advisable to leave this flag unchecked in case of process interruption, so that the products already generated have not to be computed and stored again.

Atmosphere External Sensors

By inserting this optional list, the software removes the atmosphere artefacts from the filtered interferogram stack using external sensors such as GACOS and MERIS (only for ENVISAT data).

Coregistration with DEM

By setting this flag, the input Digital Elevation Model is used in the coregistration process.

Parameters - Cluster

It brings to the cluster section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

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 - Interferogram

It brings to the interferometry 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.

Range Looks

This look factor is used as oversampling which is applyed to input SLC before the creation of interferograms according to Nyquist.

Azimut Looks

This look factor is used as oversampling which is applyed to input SLC before the creation of interferograms according to Nyquist.

Output Files

interferogram_stacking

Directory containing the following products:

•Meta files allowing to load the specific processing results (_meta).

•mean, SAR Intensity average image and associated header files (.sml, .hdr).

•IS_srdem which is the reprojected DEM in slant range.

In case the Generate Dint Multilooked for Quick View is set to True, a folder including all the tiff files "tiff_multilooked_dint" will be created. A metafile "slant_multilooked_dint_meta" will be created in the interferogram_stacking as well.

In order to distinguish the input SAR pair where each output product comes from (as well as to identify it in the connection network), a prefix containing the master-slave acquisition dates (i.e. yyyymmdd) and the master-slave relationships will be added.

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.

The window will be closed.

Help

Specific help document section.

Specific Function(s)

None.

Interferometric Stacking - Persistent Scatterers - 2 - Interferometric Process

Interferometric Stacking - Persistent Scatterers - 2 - Interferometric Process