Purpose

This functionality enables to execute, in a single iteration, the following processing sequence:

It is important to point out that, in case ENVISAT-ERS pairs are processed, the "Coregistration with DEM” flag must be checked in the interferogram generation process parameters.

The final purpose of this processing chain is the generation of a displacement map in both the azimuth (exploiting the Multi Aperture Interferometry approach) and line of sight directions.

Technical Note

Details specific to each step implemented here are described in the relevant section of the reference guide. We recommend to read it carefully.

MAI (Multi Aperture Interferometry)

It activates the decomposition of the original doppler bandwidth, in the Reference and Secondary data, into smaller portions of the full spectrum. The result of this process is the generation of an additional differential interferogram (_mai_fint), which represents the displacement observed in azimuth direction.

The input "factor" is aimed at defining how many pieces the original (full) doppler spectrum must be subdivided in: the higher the "factor" the more the pieces, which means noisier split interferograms (due to the limited doppler bandwidth exploited) but higher sensitivity to the azimuth displacement. It must be noted that in any case the sensitivity to the displacement is much coarser than in range direction. The larger the MAI factor, the higher the separation between the sub-apertures, hence the displacement sensitivity along the azimuth direction (satellite flight direction) while the band spectrum becomes smaller along with the SNR.

This functionality has been currently tested on ENVISAT ASAR, ALOS PALSAR and ERS data; the program can fail in case other sensors are used. The program requires data pairs characterized by a small doppler difference; large doppler variations can cause program failures.

Input

Input Files

Input Reference file
File name of the Reference data (_slc). This file is mandatory.

Input Secondary file
File name of the Secondary data (_slc). This file is mandatory.

DEM/Cartographic System

Reference Type

The choice is given between the three following options:

•Input DEM: the provided "Input Digital Elevation Model" file is used in the process;

•Reference Height: in case that the Digital Elevation Model is not used, the parameters needed to define the Cartographic System, the pixel spacing and the reference height are compulsory;

•DEM Download: The Digital Elevation Model Extraction tool is used to download an online digital elevation model. Various sources are available, see this section for further information.

note that the choice of one source is compulsory.

Parameters

Grid Size

The grid size of the output data must be defined; the default unit of measure is meters.

Note that - for the Geographic projection - if values higher than 0.2 are entered they will be considered as metric units and then automatically, and roughly, converted from meters to degrees; if values lower than 0.2 are entered they will be considered as degree and used as such without any conversion.

MAI Factor

Enter the number of pieces the original (full) doppler spectrum must be subdivided in.

Interferogram Generation

It brings to the principal parameters of the Interferogram Generation step. Refer to the relevant section technical note for further information about the process and other Preferences parameters.

Adaptive Filter and Coherence Generation

It brings to the principal parameters of the Adaptive Filter and Coherence Generation step. Refer to the relevant section technical note for further information about the process and other Preferences parameters.

Phase Unwrapping

It brings to the principal parameters of the Phase Unwrapping step. Refer to the relevant section technical note for further information about the process and other Preferences parameters.

GCP Selection

Refinement 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 mandatory.

MAI Refinement and Re-flattening

It brings to the principal parameters of the MAI Refinement and Re-flattening step. Refer to the relevant section technical note for further information about the process and other Preferences parameters.

MAI Phase to Displacement and Geocoding

It brings to the principal parameters of the MAI Phase to Displacement Conversion and Geocoding step. Refer to the relevant section technical note for further information about the process and other Preferences parameters.

Output

Output Root Name

Name of the output root. This file is mandatory.

Delete Temporary Files

By setting this flag, temporary files which are created in the intermediate steps, are automatically removed. All of the intermediate files are kept otherwise, refer to the Output lists relevant to each processing step for further information.

_dem

Input Digital Elevation Model resampled onto the specified cartographic system and grid size, with the associated header files (.sml, .hdr). Its areal extent is the same as the output SAR products.

_disp_cc_geo

Geocoded coherence in range direction with the associated header files (.sml, .hdr).

_mai_disp_cc_geo

Geocoded coherence in azimuth direction with the associated header files (.sml, .hdr).

_ADF

Maximum slope direction values, with the associated header files (.sml, .hdr).

_IDF

Maximum slope inclination values, with the associated header files (.sml, .hdr).

_SD

Displacement values along the maximum slope direction, with the associated header files (.sml, .hdr).

_UD

Displacement values in the direction specified as azimuth and inclination degrees (i.e. custom direction), with the associated header files (.sml, .hdr).

_VD

Vertical displacement values, with the associated header files (.sml, .hdr).

_disp

Slant Range (satellite view direction) displacement values, with the associated header files (.sml, .hdr).

_mai_disp

Azimuth (satellite flying direction) displacement values, with the associated header files (.sml, .hdr).

_disp_precision

Estimate of the data quality in range with the associated header files (.sml, .hdr). This file is generated only if the coherence file is entered as input.

_mai_disp_precision

Estimate of the data quality in azimuth with the associated header files (.sml, .hdr). This file is generated only if the coherence file is entered as input.

_disp_ALOS

Azimuth Line of Sight with the associated header files (.sml, .hdr). Positive angles are measured clockwise from the North; negative angles are measured counterclockwise from the North.

_mai_ disp_ALOS

Satellite flying direction with the associated header files (.sml, .hdr). Positive angles are measured clockwise from the North; negative angles are measured counterclockwise from the North.

_disp_ILOS

Incidence angle of the Line of Sight with the associated header files (.sml, .hdr). The angle is measured between the Line Of Sight and the vertical on the ellipsoid (flat earth).

_mai_disp_ILOS

Incidence angle for the Satellite flying direction with the associated header files (.sml, .hdr). The angle is measured between the Flying Direction and the vertical on the ellipsoid (flat earth).

Details specific to the Units of Measure and Nomenclature of the output products can be found in the Data Format section.

General Function(s)

Preview

By setting this flag, the temporary files are made available to visualize after a single step in the chain.

Delete Temporary Files

By setting this flag to false, It is possible to keep all the temporary files created during the processing. The files are located in the ENVI Output Directory in a folder with the following name: SARsTmpDir_ddmmmyyyy_hhmmss

Save

Clicking this button allows to save and close the workflow at the actual step. After saving the workflow the window will be closed

Open

Clicking this button allows to open a previously saved workflow.

< Back

Clicking this button the previous step of the workflow is shown.

Next >

Clicking this button the actual step of the workflow is performed. once finished, the next step is shown.

Next >>>

Clicking this button all the steps are performed in succession and it is no more necessary to use the "Next >" button. Make sure that all settings in all the steps are correctly set before starting with this processing.

The window will be closed.

References

Consult the reference guide specific to each processing step.

Interferometry - DInSAR MAI Displacement Workflow

Interferometry - DInSAR MAI Displacement Workflow

Purpose