The missile knows where it is because it knows where it is not…

https://youtu.be/bZe5J8SVCYQ?si=QrIlpJ6BuJADd_zF

Obviously this is a total aside, but can anyone explain what’s going on with that? Is it just explaining terrain mapping in an intentionally obtuse way, or is it some kind of parody? It’s really frustrated me because lots of people like to trot it out like a meme in the same way it was here.

	▲	Bairfhionn 4 days ago \| parent \| next [-]
		It's a joke (meme, copypasta) but it's also accurate. As I understood: Missile uses gyros and accelerometers to figure out how far it flew already towards the target. This is not 100% accurate. So it additionally uses terrain mapping to figure out how it looks down there. Compare ground (am I flying above a slope?) to its internal maps and it can figure out where it is and adjust path if off course. So it figured out the position by knowing that the position is most likely not the position where it's supposed to be.
	▲	chrisandchris 4 days ago \| parent \| prev [-]
		> Is it just explaining terrain mapping in an intentionally obtuse way AFAIK, yes, that's what it actually was (or the basic sentiment actually came from). It was some part of training video in the US army/navy (don't know exactly), but the actual story or origin remains a bit unclear. At least my search within the web did not yield any (assumingly) valid source. I think at some point it just got to "it is what it is now" because it is a very, very complicated way to explain this stuff.