[ryandamm]

Endgame is not just signal, it's inputs like GPS. Also, without external inputs, it's damned difficult to keep a lock on your location. But... not impossible.

Counterpoint, which confirms your comment: I spoke with a drone designer (DoD contract, so I won't name his company) who said he won a Red Team exercise (quaint terminology, that) against the US Armed Forces by using superior fly-without-GPS algorithm to get through a GPS suppression countermeasure. So... yeah, it's a thing.

That said, trying to do dead reckoning from a series of noisy sensor measurements isn't easy. Bias drift, quantization roundoff error (which integrates to a random walk if you're sensing rate), and filter decoherence are all real issues.