The answer is... LIDAR of course
I work for a company that makes a type of LIDAR and for internal mapping this is not a bad idea.
I came across these guys a while back that use real-time SLAM to do mapping off areas.
This is really cool (because you get to fly a drone around) but not sure you want it destroying the insode of your house! So if you want to walk around and look like a real plonker then the answer is even more clear... put a LIDAR on a spring.
When I saw this I thought I was in a surreal dream, but no, it actually works.