Methodology

MMSI (Maritime Mobile Service Identity) — 9-digit number assigned by national maritime authority

First 3 digits = MID (Maritime Identification Digit) per ITU-R M.585 — unambiguously identifies flag state

Special MMSI types: 00x (coast station), 111MID (SAR aircraft), 970 (AIS SART), 972 (MOB), 974 (EPIRB)

Live AIS position from VHF maritime transceivers — shore stations + satellite AIS for ocean coverage

Sources: MarineTraffic, VesselFinder (live), FleetMon (history), IMO registry, flag state databases