Cruise Terminology Glossary

A quick reference for the terms we use across CruiseMigration — from industry jargon to ship-tracking vocabulary.

Repositioning cruise

A one-way voyage that moves a ship between seasonal regions. Cruise lines use repositioning sailings to relocate ships as demand shifts — for example, from the Caribbean to Alaska each spring. They are typically longer than round-trip itineraries and often include unusual port combinations.

Alaska migration

The annual spring movement of cruise ships into Alaskan waters for the summer season. Most ships arrive in late April or May after repositioning from the Caribbean, Mexico, or transpacific homeports. The migration is mirrored each fall when ships return south for winter itineraries.

AIS (Automatic Identification System)

A ship-tracking technology built on VHF radio transponders. Vessels broadcast their identity, position, speed, and heading at regular intervals; coastal stations and satellites pick up the signals. CruiseMigration uses AIS data to plot near-real-time positions for the tracked fleet.

Transatlantic

A route type for voyages that cross the Atlantic Ocean between the Americas and Europe. Transatlantic repositionings typically run in spring (westbound) and fall (eastbound), and often include two or more sea days in a row.

Transpacific

A route type for voyages that cross the Pacific Ocean. Transpacific sailings connect Asia, Oceania, and North America and are generally longer than transatlantic crossings due to the greater distance involved.

Panama Canal

A route type for voyages that transit the Panama Canal between the Atlantic and Pacific oceans. These itineraries are popular repositioning routes between Florida or the Caribbean and Pacific homeports such as Los Angeles, San Francisco, or Seattle.

Coastal repositioning

A shorter repositioning voyage that follows a coastline rather than crossing an ocean. Classic examples include San Diego to Vancouver in the spring or Seattle to San Francisco in the fall. These trips usually take four to seven nights.

Gross Tonnage

A measure of a ship's total enclosed internal volume — not its weight. Gross Tonnage is the standard size metric used by cruise lines and regulators. It is calculated from the volume of all enclosed spaces using a formula defined by the International Convention on Tonnage Measurement of Ships.

Passenger capacity

The maximum number of passengers a ship is designed to carry, usually stated on a double-occupancy basis (two passengers per cabin). True peak capacity can be higher when every berth — including upper pullman bunks and sofa beds — is used.

IMO number

A seven-digit International Maritime Organization identifier that is unique to each ship's hull. The IMO number is permanent: it stays with the vessel across name changes, flag changes, and ownership transfers, which makes it the most reliable way to track a ship over time.

MMSI

Maritime Mobile Service Identity — a nine-digit number used for AIS and other maritime radio communications. Unlike the IMO number, an MMSI is tied to a radio license rather than the hull, so it can change when a ship is sold or re-flagged.