I want this, but I do not have the experience with radio signals to build this myself without more guidance. Is there a DIY proof of concept I could lean on? How much more challenging will this be if you are in an area with overlapping FM signals from 2 transmitters sending the same signal?
Would suggest to take a look at Jackson’s book on classical electrodynamics to get some intuition.
This is a very good point to start: https://www.rtl-sdr.com/tag/passive-radar/
If you have more than one receiver, the main issue is time sincronisation between the receivers.
Using the two transmitters will complicate things a lot