Wiggy
Well, there are various mature technologies available to both "see" and range-find. Some kind of combination?
Would a computer be any worse at judging these things than a human?
I'm thinking that any autonomous aircraft will of necessity have to use one of the various tech solutions for see and avoid and these should read across onto runway surveillance.
Even a laser rangefinder would do the job.
https://www.youtube.com/watch?v=_qah8oIzCwk
Yes, the system on this video is crude, but it is entirely visual based and incredibly small.
More importantly it is what a bunch of kids and hundreds of pounds can do not Boeing/Airbus with billions of pounds.