• EnvisatScanSar

Envisat ASAR ScanSAR Interferometry Processor

This processor is developed by InSAR team led by Prof. Qiming Zeng of Institute of RS & GIS, Peking University. Some of the modules in this processor are modified from similar modules in ROI_PAC. This processor can be added to ROI_PAC in order to process Envisat ASAR ScanSAR acquisitions for InSAR applications. Get Envisat_ASAR_ScanSAR_Processor.zip .

How to install this processor?

1. Make sure that you have installed ROI_PAC 3.0.0 or 3.0.1 correctly.

2. Make sure that the variables $INT_BIN and $INT_SCR are available.

3. Expand the package and enter the directory. Use the following command to install:

install.pl

4. Go to the subdirectory 'update_ROI_PAC'. If you are using ROI_PAC 3.0.0, we advise you to replace 'make_offset.pl' and 'synth_offset.pl' with the new versions which can be found in this directory. For ROI_PAC 3.0.1, you should use make_offset.pl_3.0.1 and synth_offset.pl_3.0.1. Of course, you are supposed to remove _3.0.1 before copying in this case. acpatch.F is the updated version of the azimuth compression program in ROI_PAC for ScanSAR processing. You should replace the original version in ROI_PAC with this program and complie the compression program again to get the new roi program. After that, replace the original roi program with the new one.

5. To avoid the break of process_2pass.pl, you can comment out the following codes starting from line 384 in process_2pass.pl:

• `$INT_SCR/look.pl $im12.cor \\
  • $Rlooks_unw`; Status "look.pl";
  `$INT_SCR/look.pl $im12.amp \\
  • $Rlooks_unw`; Status "look.pl";

How to use this processor?

We take the Envisat ASAR ScanSAR interferometric pair of Bam, Iran earthquake as an example to show the use of this processor. Examples of the parameter files that may be used in the processing can be found in the package.

1. Create the master and slave directories. e.g. 030902, 040608.

2. Create the DEM directory. e.g. DEM. Prepare the DEM files.

3. Create the int directory. e.g. int.

4. Edit the *.proc file, which is the parameter file of process_subswath.pl. You can find an example of this file in the package.

Now the preparation is done. Of course, you also have to prepare the orbit files needed. The folder structure is shown in the following figure.

5. Enter the master and slave directories respectively and decode the raw data using the following commands:

make_raw_asa_ws.pl ASA_WS DOR

6. Go back to the parent directory. Process each subswath using the following command:

process_subswath.pl prosubswath.proc

7. Enter the int directory. Mosaic each subswath using the following commands:

intmosaic.pl /home/lcr/bam/sub/1/INT/030902-040608-sim_SIM_4rlks.int /home/lcr/bam/sub/2/INT/030902-040608-sim_SIM_4rlks.int /home/lcr/bam/sub/3/INT/030902-040608-sim_SIM_4rlks.int /home/lcr/bam/sub/4/INT/030902-040608-sim_SIM_4rlks.int /home/lcr/bam/sub/5/INT/030902-040608-sim_SIM_4rlks.int /home/lcr/bam/int/030902-040608-sim_HDR_4rlks.int

ampmosaic.pl /home/lcr/bam/sub/1/INT/030902-040608_4rlks.amp /home/lcr/bam/sub/2/INT/030902-040608_4rlks.amp /home/lcr/bam/sub/3/INT/030902-040608_4rlks.amp /home/lcr/bam/sub/4/INT/030902-040608_4rlks.amp /home/lcr/bam/sub/5/INT/030902-040608_4rlks.amp /home/lcr/bam/int/030902-040608_4rlks.amp

cormosaic.pl /home/lcr/bam/sub/1/INT/030902-040608_4rlks.cor /home/lcr/bam/sub/2/INT/030902-040608_4rlks.cor /home/lcr/bam/sub/3/INT/030902-040608_4rlks.cor /home/lcr/bam/sub/4/INT/030902-040608_4rlks.cor /home/lcr/bam/sub/5/INT/030902-040608_4rlks.cor /home/lcr/bam/int/030902-040608_4rlks.cor

8. Go back to the parent directory. Uwrap the differential interferogram using the following command:

process_2pass.pl prosubswath.proc begin_filt unwrapped

The whole processing is completed.

Up to now, however, we still have not geocoded the interferomgram. We have not created a script that can geocode the ultimate interferogram automatically. We are still working on it.

Other functions

Additional functions of this processor includes:

1. Synchronization check of the interferometric pair.

2. Synchronization selection of the interferometric pair.

Example of Envisat ASAR ScanSAR interferometry

The following images are the differential interferomgram and coherence map of Envisat ASAR ScanSAR interferometry of Bam, Iran earthquake. These images are processed by this processor combining with ROI_PAC.

Improvements in this version

The first version of the processor was released on the page: http://roipac.org/ContribSoftware. Since then, we have fixed several problems in that version. The main improvements in this version include:

1. Removal of the horizontal stripes in interferogram and coherence map.

2. Modifications of the compression program in ROI_PAC, which can make it more suitable for ScanSAR processing.

3. More robust coregistration.

If you have published a paper that used this processor, please give an acknowledgment.

If you have any problem when using this processor, please contact: lcriah@gmail.com or qmzeng@pku.edu.cn