Phase problem (single purple color) in interferometric processing chain

[gokhan]

Hello to all!
I m trying to produce interferogram. I have 2 image data with same properties. I mean they all have the same rel. orbit number and cover the same area but after the coregistration and enhanced spectral diversity steps, when I come to make “Interferogram Formation” step, click on the Phase_ifg, I just see one single-purple color strip -nothing else- .
I did a few more trials with different data set for different area but had the same problem.

Thanks a lot in advance.

[ABraun]

Can you please show an RGB image of the coregistered image where red is master and green is slave?
Can you furthermore provide the full prouct names of the images you are using?

[gokhan]

Dear @ABraun, thanks a lot for your help.

The images are taken from Sentinel-1 SAR, SLC, in IW mode.
Sure, I also take care to be careful when choosing my area and images. Even if, I have faced with this problem in all my trials.
[1] S1A_IW_SLC__1SDV_20180918T155934_20180918T160001_023755_029731_0DD6
[2] S1A_IW_SLC__1SDV_20180930T155934_20180930T160001_023930_029CE0_341C

I am also sending Snap Out files in zipped format.
<aclass=“attachment"href=”/uploads/default/original/2X/0/018afdcbfa665a03fa10fd3739c7d2dae3f8fb4a.7z">OUT_failed_2.7z (310.7 KB)

[ABraun]

attaching dim-files alone doesn’t work, they only contain metadata.
But I will test at my computer with the provided product names.
Which IW and burst did you select for the TOPS coregistration?

[ABraun]

this is what I computed from the produts:

Are you sure the coregistration was correct?

[gokhan]

It seems everything is allright from your result @ABraun.
What I do:
1- Split processing
2- Apply orbit file
3- Coregistration - S1 Tops Co. - S1 Back Geocoding
Here, I only coregister split_orb files. “RUN”
Then, Coreg. - S Tops Co. - S1 Enhanced Spectral Diversity “RUN”
I get a file with …split_orb_stack_esd
4- Interferogram Formation step
I choose last file which is a source: …split_orb_stack_esd
Everything is default. “RUN”

But the result shows me nothing on phase information and then I can not go on.

[gokhan]

I will also tell you which IW and burst I selected.
Rightnow, SNAP is not available on my business computer.

[ABraun]

1- Split processing
2- Apply orbit file
3- Coregistration - S1 Tops Co. - S1 Back Geocoding

these should all be executed within “S1 TOPS Coregistration” and not separately. Use this as your very fist processing step.

[gokhan]

Ok, I will try again.
You did and in the selection&use of data no problem.
So, I could make a mistake in coregistration step. That might be a reason.

[gokhan]

But there is one thing which is not clear on my side.
How is possible to make all these process in one go for coregistraion

these should all be executed within “S1 TOPS Coregistration” and not separately. Use this as your very fist processing step.

?

[ABraun]

Menu > Radar > Coregistration > S1 TOPS Coregistration > S-1 TOPS Coregistration with ESD

This guides you through the different steps and creates one single output product which is the stack of master and slave. Then create the interferogram, followed by TOPS Deburst.

[gokhan]

@ABraun
I ve tried a few times and I think the problem is with my computer.
I got :java heap space: problem in my all trials. That is the main source of problem.

[ABraun]

yes, this means your computer ran out of memory.

[ga96dag]

I have the same problem, but I have more than 66GB memory left. Is there a way to clear this problem? Some days ago there wasn’t this issue.

[Niroj]

I am facing the same problem.

[chahatchawla001]

Problem with Interferogram Creation

Hi, I have been facing the same issue. For me, the source of error is the S1 TOPS REGISTRATION STEP itself. Can you please check that after stacking, the two slave and master files are generated, what are their intensity files. For me, slave goes zero all the time. Check stats thing, you can find the range of values in the file. For me they are between 0 and some small value. A quick response will be highly appreciated. Thanks!

I am also facing the same issue. For me, the slave intensity is between zero and some very small value. This renders any further step redundant and also leads to purple screen on checking phase. Can everyone who’s facing this issue kindly check their slave intensity file. Just to ask, are you all following https://media.asf.alaska.edu/uploads/pdf/current_data_recipe_pdfs/generate_insar_with_s1tbx_v4.1.pdf or similar tutorial posted their ?

[ABraun]

the intensity doesn’t matter for interferometry. As long as the coregistration was successful, no problems should be arise for the interferogram.

Please have a look at my post here and especially mengdahl’s answer on this kind of intensity image: TopoPhaseRemoval and stack

[idk]

This is chahatchawla001. @ABraun But I am getting zero slave after co-registration. Also, I have still tried and did TopoPhaseRemoval followup from the manual I have mentioned. But got nothing in DEM/ Interferrogram.

[ABraun]

if the coregistration fails, you cannot proceed with interefrogram generation.

[mwabz.a]

Hey Gokhan did you solve this issue? if yes what was the problem?