Offset tracking


Thanks for your reply!

I follow your suggestion and find the PDF as mentioned, it helps!


Thanks sir! I really appreciate your information, especially the example. Thanks for your time and consideration!


Dear @hillgrey, Sorry to reply you so late. I haven’t used GAMMA in offset tracking until now. Glad to see you have overcomed this problem.
Best regards.:grin:


Hello sir! Could you please share your experience about GAMMA offset tracking processing?


Hello @Abraun

With offset tracking. What is the minimum unit of displacement that can be identified?

I’m thinking of applying it to the slopes of hydroelectric dams that have displacements.

Thank you.


I’d say this depends on the spatial and temporal resolution of your data. It should provide enough patterns to be recognized in all images but with stable areas used for the coregistration at the same point.

Edit: don’t mind the following, I was wrong with that.
For example, the spatial resolution of Sentinel-1 is originally 3x20 m (range x azimuth, source), which is then resampled to 10x10 m. Accordingly, the observed displacement should be larger than that in some way.


That is not correct, cross-correlation between image templates can easily detect sub-pixel size movements, provided that the tracked features stay similar enough and there is no rotation for example. The window-size can be tweaked to find a compromise between resolution of the output product and SNR.

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Offset Tracking - how does the algorithm operates?
Earthquake Modeling using InSAR
Earthquake Modeling using InSAR

Authors claimed that displacement accuracy of pixel offsets techniques with Sentinel-1 can go up to 50~60 cm in azimuth resolution and 12~16 cm in range resolution. (for highly coherent areas)

That’s quite coarse compared to what you can obtain from Cosmo-Skymed or Radarsat for example. That’s the reason why offset tracking in SNAP is presented for glaciological purposes (plurimetric displacement per year).


I wasn’t aware of that, to be honest. Thank you for clarification.


Thanks to everyone for your replies


The displacement accuracy of pixel offsets that I usually see is about 1/20 of the pixel size at best and usually closer to 1/10 of a pixel. As the Sentinel-1 TOPS mode SLC products have pixels that are 14 m in azimuth, I would be surprised if the azimuth pixel offset accuracy could be less than 0.7 meters for most situations.

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