A wierd gradient over my result

Dear all
I used TanDEM-X data and made a DEM from them. Steps are listed in below:

  1. Interferogram formation
  2. unwrapping
  3. Phase to height
  4. Applying boxcar filter (5 by 5)
    But if you look at my final result, there is a blue gradient over my filtered phase to height. How can I remove it?


Cheers

Did you try out another filter to compare the result? Or did you try out the same filter using other window size?

Dear @falahfakhri
Actually I used radar----spckle filtering and then there are several options (look at at attachment) and I used all but I have all the time this blue gradient that affects on my furthure result too.

Did you check up the ground points with known altitude (you already added) in this blue patch?

OR

Could you apply your filter before phase to height conversion!

This blue patch is mostly over sea ice, not land.
I will apply the filter before phase to height conversion, I hope it works.

Ok in this case you could also try to add known altitude from nearby and then convert phase to height!

In this case you would convert phase to height two times.

I am not sure, but I believe the ramp results from smaller inaccuracies in the handling of orbit files. My colleague frequently works with TDX data and always has ramps when using SNAP.
Are these bistatic or repeat-pass data?

This is bistatic.

Yes, one of my colleges told me that he suspects it represents something of a calibration error but I do not know how it can be fixed

Why I should convert phase to height two times?

Apart form the filter process, You have this patch in your result that is right, Ok;

To convert phase to height, you have to have known altitude, and in your case they are not available Ok;

You could use your results within this patch to get the altitude points from around the patch and then reprocess again by adding these points.

have you tried to load the images separately and coregister them manually and see if the interferogram is better?

No I did not but I will do it.
Only one more question…
What are the best option in below to choose for coregistration?

I did this one in last process but still I have this blue gradient.

@ABraun
I loaded them seperately and did coregistration but the results is even worse.

Would you please to try other pairs?

Although the alignmend of fringes is quire regular: sometimes, the real structures become visible after unwrapping.

I did but it has same form.[quote=“marjanmarbouti, post:1, topic:13511, full:true”]
Dear all
I used TanDEM-X data and made a DEM from them. Steps are listed in below:

  1. Interferogram formation
  2. unwrapping
  3. Phase to height
  4. Applying boxcar filter (5 by 5)
    But if you look at my final result, there is a blue gradient over my filtered phase to height. How can I remove it?


Cheers
[/quote]
@falahfakhri I did but same shape.

Did you change the parameters of Corr , infgm formation steps, for instance, I haven’t been working a lot in TDX, but I try out to give substantive solutions.

I did unwrapping but nothing to show.