SNAP - ship detection

Hi SNAP fans,

I am following this video - ship detection using S1- GRDH product but I would like to use SLC product.

What kind of preprocessing I have to use in order to get GRDH from SLC?
or Could I follow the tutorial with SLC product?

As you have seen in the video the main processes of ship detection depend on the intensity and the calibration, In SLC image you could get also the intensity and furthermore the phase, which doesn’t play any role in here, that’s why GRDH is the right solution, might be for stable ships between two passes of SLC S1 you could focus on coherence of the objects and the shape.


Thanks for your help. I understand that SLC has phase included which is useless for this case but I have only SLC data for my AOI and not GDRH for the exact date.
I am wondering it there is a process how I can get GDRH from SLC.

Secondly, what exactly do you mean by coherence of objects?
I think to get shape of vessels could you elaborate more please?

With regard the first part of your question, you could search the GRDH products of the same AOI, by filtering this product with the scihub esa search products,


In case the GRD is not available, it’s possible to convert the SLC to GRDH please take a look at the following post,

Source of the post

Basically any stable object (in general) within two passes of radar SAR, could result a coherent object, if this the case, the stable ship could be detected as coherent object within two passes or more, however the shape of the object is important to eliminate the shape represent other things especially close to the port.

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“shape of the object is important to eliminate the shape represent other things especially close to the port”.

It is not clear for me. Could you please explain in details?

I meat not each coherent object represents ship or vessel.

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I would like to ask also question related to phase and interferometry.

Is it impossible to extract the height of offshore objects, such as offshore object which are stable 15X10m from sentinel SLC data?

I think it’s possible in case the offshore platform is within the resolution identification of S1 for instance, and the DEM should be created beforehand.

An example of offshore objects detection is here,

Source of the post

In the link is a
I know that we can detect the offshore objects but can we extract the altitude, heights?

Do we have DEM for ocean areas which could be used for terrain correction?

Hello Sir,
I am also following this tutorial and it doesnt mention any preprocessing (appart from applying precise orbit files), the sip detection Cfar algorithm is applied straight on GRDH product but to my understanding it should have been calibrated and then despeckled ? Am I correct ?