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Purpose

 

This functionality defines the SAR pair combination and connection network, which is used for the generation of the multiple differential interferograms. This step is mandatory. It is important to remember that this network can be edited at any step, from the Interferometric Workflow to the SBAS Inversion.

 

Technical Note

 

The network links created in this step are only those connecting pairs that are within the temporal and spatial baseline values specified in the relevant "Input Parameters". Those acquisitions which remain disconnected, due to baseline values exceeding the specified thresholds, are discarded from the further SBAS analysis in the standard processing .

 

At the end of the processing a graph is shown, where all connection are represented as well as the selected Super Reference. Each acquisition is represented by a diamond associated to an ID number, which is reported also in both the "CG_report.txt" file and the Edit Connection Graph>Reference/Secondary lists panel and the intermediate products file names.

The color of the diamond symbol is as follows:

▪Discarded acquisitions due to user specific constraints in red color.

▪Valid acquisitions in green color.

▪Super Reference acquisition in yellow color.

 

The following graphs are generated:

 

▪Time-Position plot, which provides the normal distance from the Super Reference (y axis) and the input acquisition dates (x axis).

▪Time-Baseline plot, which provides the normal baseline (y axis), and the input acquisition dates (x axis).

▪Time-Position Delaunay 3D plot, which provides the normal distance from the Super Reference (y axis) and the input acquisition dates (x axis). This is generated only when the "Delaunay 3D" flag has been checked. The connections here are a subset of the full redundant connection graph (i.e. "Time-Position Plot").

 

They can be reloaded and edited at any processing step by means of the relevant tool.

 

The multi-looking factors of the output Super Reference image (prefix "CG_ ") are automatically calculated by taking into account the Grid Size for Suggested Looks value, which is set in the relevant SARscape Preferences panel.

The most relevant products of this step are stored in the “connection_graph” folder.

Tandem Bistatic are accepted and correctly managed by the program.

The Delaunay 3D functionality are under maintenance.

 

Input Files

 

Input file list

Input files (_slc) to be used. This file list is mandatory.

 

Optional Files

 

Input Reference file

Name of the acquisition to use as processing reference data. This acquisition could be contained in the "Input File list" or not, if not it will be automatically added by the program. If this file is not entered the program identify the one which have the maximum number of connected acquisitions. This file is optional.

 

Parameters - Principal Parameters

 

Min Normal Baseline (%)

This threshold corresponds to the minimum percentage of the critical baseline value, which is considered acceptable in the generation of the possible data connections.

Max Normal Baseline (%)

This threshold corresponds to the maximum percentage of the critical baseline value, which is considered acceptable in the generation of the possible data connections.

Min Temporal Baseline (days)

This threshold corresponds to the minimum temporal distance, which is considered acceptable in the generation of the possible data connections. This value is expressed in days.

Max Temporal Baseline (days)
This threshold corresponds to the maximum temporal distance, which is considered acceptable in the generation of the possible data connections. This value is expressed in days.

Degree of Redundancy

After applying the thresholds on minimum and maximum Temporal and Normal Baseline for the connections (interferograms) selection, a further degree of redundancy selection criteria can be specified:

•high, all the interferograms respecting the previous Baseline thresholds are accepted.

•low, the program tries to minimize the number of kept interferograms, based on the Graph Redundancy Criteria and on Min Connection per Acquisition

Redundancy Criteria

The following selection criteria are foreseen for the removal of redundant connections, when the Degree of Redundancy is low:

•Min Normal Baseline, the number of connections is minimized by keeping only those having the smallest spatial baseline.

•Max Normal Baseline, the number of connections is minimized by keeping only those having the largest spatial baseline.

•Min Temporal Baseline, the number of connections is minimized by keeping only those having the smallest temporal baseline.

Max connections per Acquisition

Number of connections (interferograms) per acquisition remaining after skimming to reduce redundancy. This parameter indicates the average redundancy of the connection graph, and bibliography suggest setting a value higher than 5 to obtain reliable inversion solutions.

Allow Disconnected Blocks

By setting this flag the program does not discard any group of images (refer to the Technical Note) and the diconnected SBAS functionality is automatically activated for the next inversion steps.

The choices are the following:

oFalse: when the graph is not fully connected the disjointed acquisition blocks are rejected.

oAllow:  the disjointed acquisition blocks are kept.

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 - Other Parameters

 

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

 

Output Files

 

Output Root Name

Name of the output root. This file is mandatory. It is used as root name throughout the entire SBAS processing chain.

 

connection_graph folder

Directory containing the following products:

•Report file (CG_report.txt) showing various input selection parameters such as: selected super Reference, number of References, baseline and doppler values, adopted selection criteria and thresholds, etc. In case the Connection Graph is edited afterwards, the original report is updated and the old one/s is/are saved in the "work_connection_graph" subfolder.

•Entire report file (CG_entire_report.txt) showing all feasible input combination, with a complete description for each pair. In case the Connection Graph is edited afterwards, the original report is updated and the old one/s is/are saved in the "work_connection_graph" subfolder.

•Super Reference intensity image (_pwr) and associated header files (.sml, .hdr).

•Ancillary files for graph plotting purposes in ENVI.

work_connection_graph folder

Directory used to store intermediate processing results.

auxiliary.sml

Text file with process steps counters related information. This file can be edited by the user.

work_parameters.sml

Text file with process parameters related information.

work_step_performed.sml

Text file with process steps IDs related information. This file is used during the incremental processing only.

 

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.

 

Close        

The window will be closed.

 

Help

Specific help document section.

 

 

Specific Function(s)

 

None.        

 

References

 

None.