Deramping TOPSAR SLC data

For some process I need to develop, I need to deramp my TOPS SLC images. I tried several times but never fully succeded. As said by @jun_lu in this topic (Crop classification using SENTINEL-1A SLC data), it should be possible in current SNAP version even if no “deramping” operator is present in the user interface.

I spend hours (no joke) trying to deramp the images with SNAP without having to recode things my-self, using the document written by @nuno.miranda :

Here’s the procedure. My process comes from the source code of SNAP engine, in s1tbx-op-sentinel1, in the BackGeocodingOp

You probably know (or you should :wink: ) that deramping is a mandatory operation for the coregistration of TOPS SLC images. In the Back Geocoding parameters, you can output the deramp and demod phase, giving you an image of this type :

Then, you simply use _Band Maths _ to create :

i_slv_deramped = i_EW1_HH_slv * cos(derampDemodPhase_slv) - q_EW1_HH_slv * sin(derampDemodPhase_slv)
q_slv_deramped = i_EW1_HH_slv * sin(derampDemodPhase_slv) + q_EW1_HH_slv * cos(derampDemodPhase_slv)

From the image below, you see that the deramping works well

(real part of the SLC image. left = deramped, right = original)

However, we only have the deramped/demod phase for the slave image ! Unfortunately, you cannot use this to deramp the master image. Here’s and example :

We have an improvement, for sure, but we still have an important residual azimuthal component.

Do you have any idea to deramp images ? In worst cases I will modify a bit SNAP engine for my usage but if I can spare time, I will

Thanks in advance,

Quentin Glaude


If you just want to deramp/demod a subswath of a TOPS SLC product (not the output from Backgeocoding), you can use the new operator “S-1 TOPS DerampDemod”.

Thanks for the answer. This topic is however now out-of-date.

Here’s a hyperlink to current situation :