Arduino. How to determine the coordinate inside the room?

Question

Arduino

Good afternoon. Question from the DIY Arduino series.
There is a need to determine the coordinates of a certain object inside the room (note: a special person with a certain stray in his hand / pocket).
The room is a square box 25 x 25 meters.
Let's assume that there are no large objects interfering with the line of sight (walls, columns) in the room.
Required accuracy: about a meter.
Question: how to determine the XY coordinate of a person in a room using available means and technologies?
My assumption: a person has a special device that emits / reflects ultrasonic (or some other) waves. In each corner of the room (4 pcs) there is a receiver (or transmitter / receiver) of these waves. Given the delay to each receiver, determine the distance to it. Sensors like HC-SR04, but they do not have the required range.

Answer 1

Two webcams will do the trick.
Hang in the corners and on each algorithm for determining the center of an object (person). Namely - the center of mass is needed.
Knowing the distance between the two cameras, the focus of the cameras and the displacement of the object to the left or right in the field of view of each camera, you can get the distance and exact coordinates with a fairly high accuracy using triangulation.

Answer 2

Lidar ?