ALOS-2 InSAR and Ionospheric Correction package released

Added by Cunren Liang 12 months ago

The ALOS-2 Multi-Mode InSAR and Ionospheric Correction Processors have now been fully integrated into ISCE. Check out the tutorials here
https://github.com/isce-framework/isce2/tree/master/examples/input_files/alos2

The package described below is no longer recommended.

Cunren Liang





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Dear ISCE users and colleagues,

We have got permission from JPL to release the InSAR Processor for ALOS-2 Multi-Mode SAR Data and Ionospheric Correction. You can download the package from github at: https://github.com/CunrenLiang/insarzd

Currently it is still a separate package. We are working on fully incorporating it into ISCE with improved efficiency and robustness. This will be done in a couple of months. Key features of this package include:

ONE APP TO PROCESS THEM ALL
  • Support all ALOS-2 acquisition modes (except spotlight, to be added shortly)
  • Combinations include ScanSAR-ScanSAR, ScanSAR-stripmap and stripmap-stripmap
  • Support making interferograms across all the three wavelengths of ALOS-2
  • Automatic mosaicking of multiple subswaths and frames
  • Ionospheric corrections

You can find more from the readme.txt file of the package, where you will find that many advanced techniques are implemented. For details of these techniques, refer to:
1. InSAR processing:
C. Liang and E. J. Fielding, "Interferometry with ALOS-2 full-aperture ScanSAR data,"
IEEE Transactions on Geoscience and Remote Sensing, vol. 55, no. 5, pp. 2739-2750,
May 2017.
2. Ionospheric correction:
C. Liang and E. J. Fielding, "Measuring azimuth deformation with L-band ALOS-2
ScanSAR interferometry," IEEE Transactions on Geoscience and Remote Sensing, vol.
55, no. 5, pp. 2725-2738, May 2017.
C. Liang, Z. Liu, E. J. Fielding, and R. Bürgmann, “InSAR time series analysis
of L-band wide-swath SAR data acquired by ALOS-2,” IEEE Transactions on Geoscience
and Remote Sensing, vol. 56, no. 8, pp. 4492-4506, Aug. 2018.

Attached is the 2015 Nepal earthquake deformation imaged by ALOS-2 multi-mode InSAR with ionospheric corrections.

Cunren Liang and Eric J. Fielding

nepal_example.jpg (898.1 kB)


Replies (8)

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by wfm m 11 months ago

Dear Liang,
I wonder how "MAI" is implemented in your package,which has been mentioned in your article 《Measuring azimuth deformation with L-band ALOS-2
ScanSAR interferometry》.I hope to hear from you soon,than kou!
yours sincerely!
Wenfei MAO.

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by Yahui Chong about 1 month ago

Dear Liang
when I used the split range spectrum to deal with the ALOS1.0 data, I can get the right outcomes, but when I used the TerraSAR data, I can't get the right high/low band SLCs, I suspect that the split range spectrum is not support the TerraSAR data, I want to know whether you have applied the split range spectrum module to the TerrasAR data? Does the split range spectrum module support the TerraSAR data? I am looking forward to your reply! Thank you very much!

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by Cunren Liang about 1 month ago

Hi Yahui,

Range split-spectrum method is implemented for all sensors and acquisition modes supported by ISCE in different applications. I guess you are using stripmapApp.py. Check your paramters in your input file.

Ionospheric correction is not recommended for X-band TerraSAR-X data. First of all, ionospheric effects at X-band is only about 1/64 that at L-band, which, in nearly all cases, only causes negligible errors. Second of all, the performance of range split-spectrum method depends on coherence. The shorter wavelength X-band data have much worse coherence, which might lead to significant errors in ionospheric phase computation. Therefore, eventually you might get worse result after ionospheric correction.

Cunren

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by Yahui Chong about 1 month ago

Hi Cunren

Thank you very much for your recommendation! The purpose of I do range split spectrum to TerraSAR data is not to do the ionospheric correction, but to obtain lower resolution SLC data.As you have said,the signal-to-noise ratio of the data will decreases after split spectrum,I am not sure whether I can get the right interferograms through the high/low band SLC data.

Yahui

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by Francisco Delgado about 1 month ago

Dear ISCE developers,

Is it possible to user phase unwrappers other than snaphu for the ALOS-2 processor? Also, is it possible to extract a few bursts of a swath like in topsApp? I didn't see any flag for these features in alos2App.py

Francisco

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by Cunren Liang about 1 month ago

Francisco,

alos2App.py currently does not support other unwrapping method. However, other versions of snaphu can be supported. You can go to Stanford website to download the latest version of snaphu. They have made a lot of improvements recently. You can compile it and make it available from command line, then alos2App.py will find and use it automatically.

If you need burst SLCs, interferograms etc, you need to run alos2burstApp.py. However, it extracts bursts of at least an entire swath. alos2burstApp.py is slower, you are not recommended to use it unless you need individual bursts or azimuth deformation.

Processing a few bursts only is definitely not a good idea with ALOS-2 ScanSAR. First of all, unlike the single-look burst system in Sentinel-1 TOPS, it is multiple-look burst system. Multiple look means a target on the ground can be imaged by multiple bursts. If you want to process only a few bursts, you would lose some looks near image edges. Second, very small area is not good for ionospheric correction.

Cunren

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by Francisco Delgado about 1 month ago

Thanks Cunren for the information. I was thinking on using ScanSAR data for studying a small island. Definitively not ideal but ScanSAR is the only data with coherence during the time span of interest. Since the data swath is so long and the island small for the size of the swath it takes a lot of processing time.

RE: ALOS-2 InSAR and Ionospheric Correction package released - Added by Cunren Liang about 1 month ago

I see your purpose. If we process the data using full-aperture workflow as implemented in alos2App.py, cropping a small area should be fine. If we crop an area surround by water we won't lose anything in ionospheric correction. If we crop a small area out of a land area, we might get worse ionospheric correction result.

processing a small area is not yet supported. This may be added in the next version.

Cunren

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