How do they make sure tunnels are going exactly the right way?

Question

For example, when they’re digging the Euro tunnel how do they know they’re going gmthe right way and at the right depth etc.?

In: Engineering

Answer 1

Lasers! Specifically, laser-guided boring machines. [https://www.bechtel.com/projects/channel-tunnel/](https://www.bechtel.com/projects/channel-tunnel/)