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
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.
Precise measurement from fixed points of reference. In other words, if you are certain about where you’re starting (GPS) and where you want to end up (GPS) you can draw a straight line in that direction. You can carry your point of reference with you (straight down from the starting point) and the direction you need to go (compass) and the depth (multiple methods) and head out in that direction.
The measurements are checked a jillion times before starting, and throughout the dig process, especially because depth and direction will likely change over time. You then need to make adjustments to the tunneling machine to get/stay on track.
There are videos on this…digging the chunnel and through the alps.
Nowadays they use a device called a total station. If you’ve ever seen a worker beside the road looking into a device on a tripod, that looks like a complicated camera, that’s a total station. They are computerized devices that can really precisely measure the angles and distances between points.
The surveyors will establish a “benchmark,” which is a point whose coordinates are known to a high degree of precision – like, within 2 mm. The design will be based off of that benchmark. As the tunnel progresses, the surveyors will regularly mark out on the ground what is the correct direction for the workers to dig, based off of the benchmark and using a total station.
I cant answer OP’s question but just got done watching a doc on how El Chapo escaped from prison the second time and holy shit, those guys dug a tunnel starting a mile away from the prison and popped up right inside the shower stall in his cell.
Call it what you will but that was amazing to me.
Lasers! Specifically, laser-guided boring machines. [https://www.bechtel.com/projects/channel-tunnel/](https://www.bechtel.com/projects/channel-tunnel/)
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