Track Planes and Ships

Aircraft and ships announce themselves over the air, and volunteers with cheap receivers write it all down. That gives you movement history for most civil traffic and, through registries, a path to ownership. The cost: the data is self-reported by the vehicle, so it is exactly as truthful as its operator chooses. The beginner error is chasing the wrong identifier — tail numbers, callsigns, vessel names and MMSIs all change, while ICAO hex codes and IMO numbers largely don't. Resolve to the durable identifier first and everything downstream survives a rename.

Triage: which identifier do you have?