How to determine the distance between devices?

Question

Do it yourself

There was a task. There are two devices and you need to find out the distance between them. Regardless of direction... just distance. The radius of action is 10m, the accuracy is no more than 5cm ...
Let's say I put a receiver on the camera, and put the transmitter in a person's pocket. And I always know how far a person is from the camera...
I found one article where the question of how to solve this on zigbee was theoretically considered:
www.masters.donntu.edu.ua/2013/fknt/mironyuk/libra...
but I never saw a practical solution ...
In general, a two-part question:
- is it really possible to solve the problem at all?
- maybe someone who understands this issue will help to make devices?