So I work as a contracted land surveyor. This job usually means marking out locations of stuff like manholes, lights, and building corners for other people to build. The current project I am working on is at the airport nearby. This job needs me there every workday for one reason: their accuracy tolerances are impossible to achieve, and they know it.
5 millimeters. That's their elevation tolerance for this job. For you Americans, that's just under 1/4 of an inch. My surveying device alone has an elevation accuracy of 3mm, so the construction workers basically only have 2mm to work with.
So what really ends up happening, is they need me to cheat numbers. Sometimes the elevations are close, but more often than not, I'm spending my time raising and lowering numbers to match the design. The engineers know that this is happening, but they turn a blind eye to it because they need to sign off on what I give them so that they can say "yup we're all within spec." This has been going on for decades, and the airport seems none the wiser.
And you know what? The accuracy that they end up with, is actually pretty good. It's 20mm instead 5, but that is good enough. I just recently flew on the runway that I surveyed last summer, where I was constantly adjusting numbers, and it was really smooth. I've heard pilots say that that runway is the smoothest they've landed on and taken off from.
Basically, I have a job right now because there are still people who sit at their computer all day looking at the numbers I send in, instead of the big picture. I guess I should be thankful.