I have to say that your simple question has a very long answer. An inspiration for an essay. Would have to cover classic methods of mine surveys and the various ways of representing complex 3D structures on 2D sheets of paper; followed by the modern revolution of LIDAR mapping and 3D CAD models.

I have used a sun compass to collect orientation data on highly magnetized outcrops. Hell, I’ve had credits cards in my wallet lose their magnetic data because of sitting on magnetite rich rocks. And if you are in an active mine, there are often high voltage powerlines nearby (like right next to you, when you are ankle deep in water), which totally screw with a compass.

The magnetic north pole is moving so rapidly that they have had to rush out an update to the magnetic map…

Additionally, have you experienced any issues from local deposits affecting the local magnetic field?

notebook, clipboard with grid paper, hardhat, headlamp, steel toed boots, colored pencils, no fear of bats, rescue O2 pack, weatherproof gear (underground is wet and muddy), rock hammer, a vest to put all this shit into plus some snacks.

Rule of thumb: typically, mine levels are about a hundred feet apart in elevation / depth.

I have always wanted to visit the Homestake mine:

https://abandonedminemodels.com/south-dakota

Anyone that points out the problem is NOT solved is dismissed as a fool, a coward, or evil. Trump simply doesn’t care about the North Koreans missile threat, or the Iranian nuke threat, or the Russian cyber threat. All he cares is that his followers admire his strength, his intelligence, and his courage. Conversely, he is determined that his followers see his opponents as foolish, cowardly, or evil.

We’ve known this since the beginning, when he insisted his inauguration crowds were bigger than anyone elses.
Even though it didn’t really matter, and no one cared, it was simply a fact about one of his claims (albeit a minor and insignificant one) that could be demonstrated to be false, so it was a threat to his legitimacy. He fears his legitimacy can be questioned because he was elected by a minority of voters, and he has always questioned the legitimacy of his enemies with insults, derogatory nicknames or outright lies. He must be aware (at least, I hope he is!) that most people see this, but he is not interested in “most people”. He is interested in his base. He knows how religious cults work, and they do not require belief in the unbelievers, they only demand complete belief from the congregation.

None of this is particularly unusual or surprising. What I find terrifying is that about a quarter to a third of the American public falls for this. We don’t just have a pathological President, we have a profoundly ignorant country.

The orange one saw a video of one tunnel entrance getting blown up. That as evidence of the underground facility being destroyed is stupid. But, he is.

Here’s a nice site of virtual mine models (not mine) for reference:

https://abandonedminemodels.com/

There will always be a misguided nostalgia for the past, or at least our idealized memory of it. We were young, we were strong, we were on the ascendant, so we tend to project our feeling of past vigor and dynamism onto everything and everybody. Make America Great Again, as if it ever was, or as if it isn’t now. Do we run the risk of it all “ending in disaster”. Yes we do, but that is the price we have to pay, and there are no guarantees. To be of value, to be remembered, experience has to be painful. Like freedom, the price of truth is blood and tears.

No, we need to learn our lesson, we need to hurt, to lose something, or we will not remember this time and this aberration and betrayal of everything that is good and decent about this country. Our memories of Stalin and Hitler, of Franco and Mussolini will always come back to haunt some of us, those who can’t find happiness in a more tolerant and decent world, but most of us will learn the lessons of history provided they are applied sternly and forcefully enough. In our Skinnerian world, negative reinforcement works, even if only for a generation.

Trump will cause damage and grief, true, but if we magically sweep him away, if some accident of history removes him, he will only come back in some even more horrid form tomorrow. Remember, his followers claim he “speaks to them”. After he goes they will remain. They must learn, the hard way, that he is speaking only lies.