You can build your own SAR system pretty easily, but of course the really cool stuff results from being able to fly a plane or in this case have some satellites. The PDF for Experiment 3 here https://ocw.mit.edu/resources/res-ll-003-build-a-small-radar... shows an example of using a weak 2.4 GHz system on the ground taking snapshots every two inches for 10 feet or so, facing down a road towards a warehouse. A visualization algorithm is overlayed on top of a satellite image to show that the system can at least detect front surfaces. The professor has also built other hobbyist high-frequency systems before, including demonstrating through-wall capabilities for some of them. This PDF (others on his site) has some good examples of what the environment looks like with a camera, and what you get when you process some SAR data with matlab into a 2D image: http://glcharvat.com/website%20pdfs/Charvat_MIT_Haystack_DIY...