Interferogram and Displacement Comparison between SNAP and DIAPASON in GEP

[vin15carter]

Hello,

I try to obtain interferogram and displacement images of “Japan Earthquake April 2016 M7.3 Kumamoto” by processing Sentinel-1 images on SNAP. There was a similar work which processed the same sentinel-1 data but on another platfrom GEP (The Geohazard Exploitation Platform). They used DIAPASON processing chain which is available on the GEP. So that I can compare SNAP results and DIAPASON results. Although general interferograms look similar for ascending data, SNAP results look more noisy and DIAPASON results looks smoother and have nicer look. Well for descending data two results are quite different. And I really wanna learn the cause of that difference. DIAPASON results look nicer to me.

Note: After phase unwrapping two results look quite different for both asc and desc. But I will leave that part after we configure the reason for interferogram difference.

Data-Asc

• List item Pre (08/04/2016), S1A_IW_SLC__1SSV_20160408T091355_20160408T091430_010728_01001F_83EB
• List item Post( 20/04/2016), S1A_IW_SLC__1SSV_20160420T091355_20160420T091423_010903_010569_F9CE

Data-Desc

• List item Pre (03/03/2016), S1A_IW_SLC__1SSV_20160303T211629_20160303T211657_010210_00F131_E721
• List item Post (20/04/2016), S1A_IW_SLC__1SSV_20160420T211630_20160420T211658_010910_01059E_8779

The same data used. There was only VV polarization bands in the products.

I followed the same steps at “Sentinel-1 TOPS Interferometry Tutorial”. Basically the steps I followed are:

Step 1 ) S-1 Tops coregistration (I choose subswath and burst for the region)
Step 2 Interferogram formation
Step 3 ) S-1 Tops Deburst
Step 5) Topographic phase removal
Step 6) Goldstein phase filtering
Step 7) Terrain Correction

Step 8 …) I leave phase unwrapping part for now.

I used the default parameters for each operator.

Result are provided below. For details of DIAPASON results please look at the following presentation which I took the images. “GEP Diapason services for differential interferograms generation”

DIAPASON Asc

SNAP Asc

DIAPASON Desc

SNAP Desc

SNAP Desc On Google Earth

I guess I provided enough details.

Well for asc interferogram, patterns look similar however quality looks different. SNAP results seems more noisy. DIAPASON results look smoother. Is it just related with visualizing, or is there any intermediate step that I miss to apply? Well at Goldstein phase filtering step I increased window size and assumed to have less noisy result, but it didnt change anything.

For desc data, interferogram results are quite different. Maybe at coregistration step there could be algorithmic differences of two platform. Well I really have no comment here.

Your help will be appreciated.

Thanks.

[mengdahl]

The Diapason-phase look much more heavily filtered. I assume that you used the same orbit data for both SNAP and Diapason descending pair? It looks like there could be some issues with the co-registration of the the SNAP descending pair since fringes are missing in the right side of the scene.

[css]

The SNAP Desc screenshot only shows a small area towards the centre and left of the DIAPOSON Desc screenshot.
But for that smaller area the interferograms from both software tools seem to match quite well, at least in a similar way to how the ascendings interferograms match.

[vin15carter]

Yes more heavily filtered, they maybe used another filter I really dont know but it looks nicer. Yes I used exaclty the same data, since they provied that clearly on their presentation. Well yes, the first thing that comes to mind is coregistration for desc case. But not only right part, there is no similart even at the left part. Interesting…

[vin15carter]

Asc case looks quite similar but I really cannot see any similarity at desc case. I’ve done the steps twice on SNAP. Do you see any similarity on desc case?

[css]

I have cropped the area in the centre and centre-left of your DIAPASON Desc screenshot.
It looks like this:
DIAPASON Desc cropped

To me, it looks ‘similar’ to the SNAP Desc screenshot.
SNAP Desc

[vin15carter]

Oh yes you are right, so I take more burst from IW2 and general pattern look the same also for desc part, very similar to asc case. But again little more noisy. When I compare intefergoram and coherence band, they are consistent. So in somehow, they increased the coherency and obtained more nice looking fringes or they heavily filtered result. But at the end we cannot obtain it with SNAP.

DIAPASON Desc

SNAP Desc Interferogram

SNAP Desc Coherence

[Shivendra009]

Hello everyone
Can anybody suggest me what information can be derived from this interferogram, as i am unable to get some sort of fringes. What do these color gradients on mountain slopes indicate.

Please help

[ABraun]

please have a look at this topic:

Some explanations about concepts of fringes of interferogram and coherence

Dear all, The phase difference can have contributions from five different sources: Δφflat is called flat Earth phase which is the phase contribution due to the earth curvature.  Δφelevation is the topographic contribution to the interferometric phase.  Δφdisplacement is the surface deformation contribution to the interferometric phase.  Δφatmosphere is the atmospheric contribution to the interferometric phase. It is introduced due to the atmospheric humidity, temperature and pressur…

[nathanielgeo]

Hello vin15carter,

This is a great post and is very helpful.

Thank you very muchly,

Nait