Offset Tracking Issues in SNAP using S1 imagery

Dear Snap users,

I am needing to undertake some feature tracking of two glaciers in Iceland using Sentinel imagery. I have had the SNAP toolbox recommended to me and hope to use it to good effect.

I have been trying to work through the processing steps, following both the tutorial from ESA for Rink Glacier, as well as the tutorial from a webinar given earlier this month by RUS for Petermann Glacier (link:

I am following these steps extremely closely, yet I have been unable thus far to obtain any sort of velocity output. I have been attempting to overcome these myself by reading through posts on the forum, and then retrying myself, but I am still stuck with the same issues.

Currently, my ‘best outcome’ has been a velocity map made up of randomly spaced squares, which obviously isn’t the outcome I need. I read on a post on this forum that I should check the geometric quality of my stack (using RGB) but have no idea how to do this - can any of you help?

Apart from this outcome, the other issue I have is that when I try to load the bands after undertaking the DEM-assisted coregistration nothing will load? Instead the screen where it should appear remains grey. I leave it to load for a while but still nothing. Any hints on why this may be occurring?

As I said, I am following the steps in both tutorials very closely (they are ever so slightly different but main steps are the same - apply orbit file > DEM > Subset > Offset Tracking. So I am struggling to see what I’m doing wrong?
I understand that I will need to play around with the parameters in the offset tracking stage as my glacier is much different to the ones in Greenland, but I do know it flows at max. 2m a day.
My computer has 16gb of RAM if that’s any help in answering the questions.

Thank you in advance.

Make an RGB from 2 or 3 images of your AOI and see how the glacier movement looks like visually. What DEM are you using? For co-registration a low-resolution one like the GETASSE30 will do.

Hi Markus, thanks for your reply -

What do you mean make an RGB exactly? I’ve had a look in SNAP and I guess you mean right click on a layer in the Product Explorer window and then select ‘Open RGB Image Window’, and then input a different layer for each band? so my first image would be red, second green then first/second is blue? Correct?
And a RGB of what? The offset tracking output? (I apologise for the questions, I just really don’t know what this all means)!

For the DEM-assisted co-reg I was using the ACE30 DEM - but am running the processing again with the GETASSE30 DEM to see if any difference.

RGB of your input images, taken on different dates, so you can see whether the glacier has moved or not.

The DEM-assisted coregistration either works or fails due to the DEM. If yours already worked no good reason to change the DEM.

Ok - got you - there is some displacement, so it has definitely moved over the period of 12 days. AS I said in my original post the glacier moves at around 1.5 - 2 m a day, so over 12 days in the summer we should be looking at at least 15 m of movement, if I’m correct.

So as the RGB has confirmed movement, any idea why my final velocity map either doesn’t show at all (just a grey screen) or gives the little squares?

I saw in a different post that instead of DEM-assisted co-reg I should just use the normal coregistration tool?