Hi there,
I finished my work near Mosul Dam. The previous literature stated that there is a subsidence in the dam. I got the final result that the range of the measurement is between 4.42 and 46.78 abs_phase. there is no scale and it looks uplifting and there is no subsidence. Is there any tip.

you have to run phase to displacement first.

Thanks dear Braun,
You mean before exporting to XMZ or before before Range-Doppler Terrain Correction?
Moreover, how can I run phase to displacement?

Where I did the following steps to complete the DNiSAR:

  1. Coregistration of data
  2. Interferogram Formation
  3. TOPS debursting
  4. Topographic phase removal
  5. Goldstein phase filtering
  6. Multilooking
  7. Export the result of step 5 to SNAPHU
  8. Unwrapping
  9. Import the result of SNAPHU
  10. Range-Doppler Terrain Correction
  11. Export the result of step 10 as a KMZ
    If there is any mistake, please tell me about it.

after importing the unwrapped phase and before range doppler terrain correction.

Hello, values that are shown colour legend “abs_phase”, these values correspond to the meters?

Thanks a lot


When performing the steps for deriving a map subsidence at the end, I am wondering whether we need to perform terrain correction before of after unwrapping? I did some experiments between unwrapping the phase after performing terrain correction and phase unwrapping before performing terrain correction. The results are shown below:

The image on the left shows the phase unwrapping which performed after the data has been terrain corrected. For the image on the right, the unwrapping phase were performed firsts and the it was terrain corrected.

We see that the difference between the two images is large. It seems that if we terrain correct the SAR image first before phase unwrapping, the results we get are very different. Why does terrain correction change the results so much?

So, is it recommended for terrain correction step to be done at the very end?

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Yes, terrain correction is a final step.

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I would have said that, too, but that still raises the question why the left image (tc before unwrapping) looks so well compared to the other.