Urban area

How can I get the precise footprint of urban area on subswath and burst on s1 slc image?
and in which step I should merge images?

Please have a look at this wonderful tutorial by the EO College: https://www.youtube.com/watch?v=JslESstEIVw

It makes use of backscatter intensity and InSAR coherence and explains how to process SLC data.

thanks alot