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

They plan before they dig. If they want to dig east, they get a compass that points them east. If they want to go down, they get a level that shows them what “flat” looks like and aims down from there.