Long-Range Identification and Tracking
Abbreviation: LRIT
Mandatory worldwide ship-position-reporting system at 6-hour intervals via Inmarsat-C (or Iridium), separate from AIS.
In practice
Configured by the flag-state Application Service Provider. The bridge officer verifies LRIT 'system OK' on the daily checklist; communication-loss alarm appears when the satellite link drops for >25 hours.
Regulatory detail & full definition
Required by SOLAS Ch. V Reg. 19-1 for passenger ships, cargo ships >= 300 GT on international voyages, and offshore drilling units. Position is reported to the flag state's LRIT data centre, which may share with port states (within 1,000 NM of coast) and the IMSO (International Mobile Satellite Organization). Distinct from AIS — LRIT is encrypted and not publicly viewable.
Authoritative source: SOLAS Chapter V (Safety of navigation) ↗
Related
Source: SOLAS Ch. V Reg. 19-1; IMO MSC.263(84) LRIT performance standards
High confidence
Editorial confidence: how we grade.