SNAPHU Software

[jefriza]

It works, It takes times 6 hours for 31000 lines.

I did for 23726 and take time 5 hours.

and here is the result in .kmz file after TC. It is not create fringes at all.

Thank you for your comments

[ABraun]

strong ramp in this one. If you look closer, is there any topographic information on this one?
Did you apply topographic phase removal? What is your goal?

[jefriza]

I did topographic phase removal.

My goal is to calculate fringes based on interferogram achieved.
I want to see landslide movement in that part (Central of Aceh District). Based on ground data. there are a lot of landslide in October 2015.

[ABraun]

did you have good coherence between the images? Maybe you can post a screenshot of the coherence raster and its histogram.

Which snaphu method did you allpy? TOPO, DEFO or SMOOTH?

You could also consider making additional interferograms based on other image pairs, before and afterh October, just to get an impression on the general information which can be retrieved from the data.

S1 Tops coregistration

Avalanches surely destroy coherence completely.

Unwrapping - results differ from tutorial

Please keep in mind that subsidence measurements from one or a couple if interferograms cannot be trusted due to the presence of atmospheric artefacts.

[jefriza]

I attached of histogram in Takengon city (Near Lut Tawar Lake).

I apply DEFO (Deformation in Snaphu method)

I have 5 data:

S1A_IW_SLC__1SSV_20151226T115029_20151226T115057_009213_00D472_F55A
S1A_IW_SLC__1SSV_20150828T115035_20150828T115102_007463_00A49B_3DB3
S1A_IW_SLC__1SSV_20150921T115036_20150921T115103_007813_00AE01_C390
S1A_IW_SLC__1SSV_20151202T115030_20151202T115058_008863_00CAA0_4976
S1A_IW_SLC__1SSV_20150711T115032_20150711T115059_006763_009132_6682

I sellect 21 Sept 2015 as a master image, and 2 Dec 2015 as a slave image.

I have not repeat interferogram to other slave image yet.

I studied that large land movement for 2 m above can destroy fringes. but I am still lack study about atmospheric artefacts can be destroy fringes too.

[ABraun]

theoretically, only the white areas in your coherence image reveal usable information. Then there are still atmospheric disturbances left which could affect your fringes. Try to apply a coherence mask on your interferogram as described below to see if the areas of interest are within that areas.

Subsidence map in 3d view

right-click on the unwrapped phase, in the menu you find properties. There is an entry "valid pixel expression", where you enter something like coh_HH_11Feb2008_04Mar2008 > 0.6. Of course, the coherence name should be yours and the threshold can also be lower. Some say acceptable quality begins with 0.3 already.

If the areas of interest are excluded by this mask, you need better coherence. You can achieve that by using an image pair with smaller temporal baseline (6/12 days are currently the smallest for Sentinel-1). You can also try to apply a better co-registration in order to improve the image alignment.

[jefriza]

I will work on that.

There only 24 days available data S1A on that area. I could not have 12 days or 6 days data

So how to do better coregistration.

Thank you for answering all my questions

[ABraun]

maybe one of these points helps:

Radarsat 2 coregistration

You can increase the number of GCPs for the coregistration. This could lead to better results at some locations. Also try to use a second order polyonomial and trucated sinc interpolation. These things won’t increase the overall quality of the data but baybe lead to smaller improvements.

[mengdahl]

24 days is simply too long to allow for higher coherence. 12-day data should be available over your area by now.

[jefriza]

Thank you Dr Marcus Engdahl and Dr Andreas Braun for your comment.

There are 6 days data availabe in the same sensor S1A:
S1A_IW_GRDH_1SDV_20170107T231936_20170107T232005_014732_017FB3_85B8 and S1A_IW_GRDH_1SSV_20170113T115035_20170113T115100_014813_01821F_62DD

is it ok if I coregistrasion and make interferogram from these image (I will chose VV polarization). I doubt GRD mode can not produce any interferogram.

Thank you

[lveci]

GRD only have amplitudes. You need complex data for interferometry. You need the SLC products.
https://sentinel.esa.int/web/sentinel/user-guides/sentinel-1-sar/product-types-processing-levels/level-1

[jefriza]

Thank you for replay Dr Luis Veci

I got 5.52 day times differences but perpendicular baseline is -1169553 meter. Is it ok to proceed ?
S1A_IW_SLC__1SDV_20170107T231936_20170107T232006_014732_017FB3_2E70.zip (Master)
S1A_IW_SLC__1SSV_20170113T115034_20170113T115102_014813_01821F_5F0D.zip (Slave)

[jefriza]

unfortunately, I can not proceed SLC data because on 7 Jan 2017 1SDV, I need IW1 VV pol and on the image 13 Jan 2017 1SSV, I need need IW3 VV pol . It has different IW.

So no data for that particular area below 24 days for SLC.

I though Sentinel 1A and 1B should have 6 days data in that particular area.

Thank you for any comment

[ABraun]

right, you need products of same polarization. But not all areas are covered equally, as you see here:
https://sentinel.esa.int/web/sentinel/missions/sentinel-1/observation-scenario

[jefriza]

Thank you Dr Andrew Braun.

yes, same polarization but not same IW number can not proceed Dr Braun, is is right?

one more thing,
low coherence will affect interferogram. a lot of site in Indonesia, especially in Aceh Tengah, low coherence is presented due to high vegetation. It means I have to elliminate result of DinSAR and can not use Sentinel data to produce a good interferogram due to atmospheric disturbance.

I read some papers. It is low coherence present but at least unwrapping phase can be proceed to D-InSAR with other sensor such as ALOS.

Sorry out of topic, I should move to another topic, but don’t do where to put. just go through my question and answer

Thank you for comment

[ABraun]

every SLC product consists of 3 sub-swaths (IWs)
If your images are taken within the same track (which means they geographically align and have the same extents) there should be no technical problem using them for interferometry.
You can use the TOPSAR Split module to select only one of the three sub-swaths to decrease the file size.

About coherence: It is generally destroyed by vegetation cover. But if you use long wavelengths (ALOS PALSAR) you have higher chances to penetrate some of the smaller vegetation and get coherence from the surfaces. This however ends at high canopies.

Some more points to consider:

Radarsat 2 coregistration

Maybe a few points: Coherence stronlgy depends from the land cover. Much vegetation leads to decorrelation between your images and low coherence. Where is your data located? Can you post a screenshot of your coherence? You can increase the number of GCPs for the coregistration. This could lead to better results at some locations. Also try to use a second order polyonomial and trucated sinc interpolation. These things won't increase the overall quality of the data but baybe lead to smaller impr…

Subsidence map in 3d view

thank you, @heinzollerketchup. Generally, the longer the temporal baseline (=the time between two images) the higher is the decorrelation which leads to small coherence values. It also depends on the cover of the analyzed surface. Bare ground mostly shows slower decorrelation than one with high vegetation cover. As you can see here (tested with S1 data), coherence decreases from 0.7 to nearly 0.1 within 6 12-day-cycles (12, 24, 36, 48, 60 and 72 days, blue to red) [image] Source: http://iee…

[panda1]

Dear ABraun：
I am a new user of SNAP, according to the tutorial you given above, the smooth installation of cygwin and SNAPHU, but when I put the contents of the red box on the contents of the paste -ENTER, there is a problem shown on the picture,I did not get the desired result，and I do not know why, Hope to get your answer, thank you very much!

[ABraun]

ntents of the paste -ENTER, there is a problem shown on the picture,I did not get the desired result，and I do not know why, Hope to get your answer, thank you very mu

somehow the file extension *.conf is not recognized by your command. Try renaming it to snaphu.conf and run again.

[sentinelgyb]

When I was installing the cygwin , it says the following error. Could you help me solve this problem. Thanks.

[ABraun]

I’m not experienced with cygwin so unfortunately not. But you should try a server which is a bit closer to you than Esslingen in Germany