Range doopler corection change pixel position in diferent images

Hi everybody.

First to say that i am beginner processing Sentinel 1 SAR images. I am working on ground range detected S1 SAR products. I am using the processing chain showed below:

  1. Thermal noise removal
  2. Apply Orbit file
  3. Calibration to Beta0
  4. Speckle filtering
  5. Radiometric terrain flattening
  6. Range Doppler Terrain Correction
    Everything is going well untill the range doppler corection. In radiometric terrain flattenin step i compare the relative pixel position in the same coordinates for two differents dates. I will show a super zoom.

As you can see, the pixel position is the same in two differents dates. Then i apply range doppler correction and the relative pixel position is not the same, even applying the same parameters to the doppler step. And the fixed structures as houses, are displaced from one date to another. I will show a super zoom of the relative pixel position.

i will show the doppler correction parameters in the next post.

Can anybody tell me what it’s happening and how to solve it?
Thank you in advance.

Range doppler corection parameters:

DEM-Assisted Coregistration solve the problem. Thank you all.

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