I am new to SAR image processing, I have a SAR sentinel 1 dataset downloaded from ESA site: S1A_IW_GRDH_1SDV_20190314T030905_20190314T030930_026328_02F196_2EC3

I am trying to do terrain correction via SNAP sentinel 1 toolbox using Range Doppler Terrain Correction.

My Region of Interest (is a coastal area)

RAW image of the SAR data in SNAP

I try to perform Range Dopler Terrain Correction with the default parameters.

The result generated is a blank map where there are no values:

The result from the Range Dopler Terrain Correction

Am I missing something? I understand the SRTM data is use correct the terrain. However, since my data is near the coast and considering the accuracy limitations of the SRTM data is it removing the entire remote sensed values considering they all are below mean sea level?

Below are the parameters for Terrain Correction using Range Dopler Terrain Correction: Parameters for Range Dopler Terrain Correction causing the issue

  • I also having the same problem, > i have two images of the same place.. it performs the terrain correction for one but does not for the other. How did you solve the problem?
    – Neloy
    Nov 6, 2019 at 6:15

1 Answer 1


This is a known issue and caused by inaccurate access to the SRTM 3Sec (Auto Download) data which is required for the terrain correction. Usually, it is automatically downloaded but the access changed.

Solution: Please install the latest internal updates (see image below) of SNAP and restart the software. Additionally, I recommend using the SRTM 1Sec (Auto Download) because of its higher resolution and smaller tile size (mostly reduces downloading time). Furthermore, it is not affected by the issue mentioned above.

enter image description here

  • The problem persists even after installing the updates... moreover i have two images of the same place.. it performs the terrain correction for one but does not for the other.. any idea ???
    – rao
    Oct 31, 2019 at 7:54

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