Help Content > Interferometric Stacking > PS & E-PS > 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 " Reference 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 Secondary (i.e. "Input File List") using always the same Reference 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 Reference image (i.e. Super Reference 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 Reference 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 Reference 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 Reference 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.

Optional Water Vapour File List

File list with water vapour data GACOS products (_filename_list.txt; *_bil; *_geo). When the list is initialized and compiled, the software will remove the water vapour component from the interferograms (*_zpd_dint). A GACOS raster must be inserted for each input image (same date and time of acquisition). The couplings are made automatically by the software. This file is optional.

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

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 - Atmosphere

It brings to the atmosphere and general 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 applied to input SLC before the creation of interferograms according to Nyquist.

Azimut Looks

This look factor is used as oversampling which is applied 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 Reference-Secondary acquisition dates (i.e. yyyymmdd) and the Reference-Secondary 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