Making interferogram for TANDEM-X bistatic mode

  1. Only use the elevation generated by InSAR as the input (as you did)

  2. Using the ASTER here is totally fine. Make sure you check “DEM” in the terrain correction step. This writes the ASTER DEM in UTM coordinates into your target product so you can compare later.

  3. Uncheck “Mask out areas without elevation”

  1. If you do this with the InSAR elevations of both dates, the results will be of the same size and coordinate system and then you can select “Radar > Coregistration > Stack Tools > Stack” to bring them into one final product.

I made elevation result and the ASTER DEM in UTM coordinates (figure1) but it seems a little strange although I did not work with DEMs but why the ASTER DEM has DEM over some area of ice and does not have DEM over other parts?

Have you checked how the ASTER dem looks in the mosaic?

Are you sure what we see is not the ACE30?

ASTER has 30 meters spatial resolution which is resampled to the resolution of the TDX data.

This is something that I got from mosaic.

I also put it on google earth and seems ok about location.

does it really look like this in your study area?

This is the image I have (green one).

I am trying to make a KMZ file from my result to see, if it is matched or not but then it gives me this error.

This is that area and is matched with DEM.

The area is right but I do not know why ASTER is in course resolution.

I downloaded this one,

Is it right?

Another idea, I made a mosaic and I think the resolution was changed after making mosaic.
Yes. Now I got the point, making mosaic reduces resolution.
Any idea about it?

that’s possoble. You can use the measure tool to see how large the single pixels are.
I see that you have just updated your post. Strangely, the DEM was resampled for mosaicing.

No the problem is with mosaicing…look at this

I just tried it with SRTM and they area also resampled to a lower reslolution.

I found its solution. We should manually adjust it.

good that you found a solution.
Orthorectifying the DEM doesn’t make much sense to me. But as long as the result is not distorted, everything is fine.

Dear @ABraun

If you remember, I tried to make DEM for 18 and 29 May (for example HH). Result of 29th May was fine but I think something goes wrong with unwrapping 18th May (figure1, 2,3).

I think because we have water in our interferogram (figure1). I do not know how SNAP does unwrapping and from where it starts to do.

How can I find unwrapping code or method that SNAP uses it for unwrapping? Do you have any idea about it? How this error would be solved?

Figure1. Interferogram

Figure 2. Unwrapping

Figure 3. DEM

you can mask out low coherence areas in the image using a valid pixel expression as described here: Subsidence map in 3d view) but this unfortunately doesn’t affect the uwnrapping process.

I don’t know how these can be excluded from the unwrapping but the basic algorithms are explained here:
Chen and Zebker are the authors of snaphu, unfortunately, the page is currently offline: https://nova.stanford.edusar_group/snaphu/

Thanks but by this way, it only affects on coherence result, not interferogram. So, again unwrapping would be failed.

One more question,

Is it possible that I use ‘special subset from view’ over interferogram and subset my area of interest OR should I do this over intensity before making interferogram?

It does, you use low coherence values to make these areas no data in the interferogram.

To your second question: this is possible for must sensors besides Sentinel-1 because of the bursts. Subsetting the interferogram for TSX/TDX is no problem!