What are Ship Numbers & Different Types of Ship Identification Number Systems

Ships have various means of being identified. While the transponders present of ships can make their location easy to trace by a satellite system, all over the world, an identification system allows giving an exact name to the ship that denotes its characteristics.



This makes a universal ship identification system that allows marine authorities all over the world to identify a ship and its features. However, a common ship identification system exists, but each country may have some modifications.


What are ship numbers?

For someone who is unaware about technicalities of shipping world, a ship identification number would be a new thing. To tell them, a ship number is a unique ship identification number issued to the ships by an authority. Under varying systems of ship numbering, different types of ship numbers have been allotted to ships in the past. Some of the ship numbering systems includes the following:

Global shipping number system

This kind of ship numbering system is mainly based on the information of the ship’s type, its building place and time of its construction. This ship numbering system developed somewhere in 1998. This system is based on specific information like place and time of manufacture of the ship. The basic idea of the GSN system is to assign a unique 8 digit number to every ship. However, the main source of this database remains the information of ships already available.

Example a ship data for which has been obtained from British Shipbuilding database will be provided a number in series of 2xxxxxxx. The unique first digit marks the identity of each ship. But there are chances of one ship appearing in more than one database, hence being assigned multiple GSNs.

Listing by the Hull number

Another system of ship numbers famous mostly in US navy; this is a rather old system which dates back to 1880s. However, a newer version of this system was introduced somewhere in 1920 when the information of ships in US navy was combined using their hull number mentioned for every ship and a unique alphabetical code assigned to the ship.

The alphabetical code could be a single letter or two letters code that mainly denoted the type of ship and the purpose it was used for, example AB stands for crane ships, AF for store ship, AFS for combat store ships, AM for minesweepers, AB for net laying ships etc. This alphanumeric system of ship identification was derived from the unique codes common among the people tracking ships by their hull numbers. Although this system has been in use for many decades now and has undergone certain changes over the time, it is still a popular system of ship identification number.

Pennant number

This is another type of number allotted to ships for their easy identification. Used mainly in some parts of Europe and the modern Royal navy, this system uses the information about the ship depending on its type. A specific number is assigned to each ship depending on the type of ship to which a letter code is added which makes a unique pennant number for every ship. The numerical code can precede or succeed the letter.

Depending on position of numbers in this code, it can be called flag superior or inferior. However, the more important thing of this ship identification system is the capital letter to every ship that marks its type or use. This system of analogous to the more commonly used Hull number identification system used in other parts of the world but is also used for ships of other countries. This system is most important because of its universal application, ease of use and unique characteristics.

IMO number system

One of the most commonly used and popular system of ship identification is the IMO number system. This is the numbering system issued by the International Maritime Organization. This number is one of the most important of the ship numbers. It consists of a seven digit number preceded by letter IMO. It is assigned to every seagoing vessel of 100 GT or more. As a part of the regulation looking into ship identification, it is important that IMO number vessel must be marked on the vessel all the times at places where it is easily visible.

However, it is important that this number should not be confused with the official number issued at time of vessel’s registration. IMO number vessel is assigned by Lloyd’s Register-Fairplay Ltd on behalf of IMO, solely for purpose of identification. This is a unique numbering system and is followed internationally making it one if the most commonly used numbering systems. It is also important to mention that while it is necessary for every seagoing vessel to be an IMO number vessel, there are certain exceptions that can be made like pleasure yachts, hopper barges, hydrofoils, air cushion vehicles, floating docks, ships engaged on special service, ships engaged in fishing etc.

MMSI numbering system

Another ship identification numbering system involves use of a Maritime Mobile Service Identity (MMSI) number. This is a nine digit number which is transmitted over the radio channels to be picked up by earth ship stations all over the world. This number is also unique for every ship and serves dual purpose of ship identification and course tracking. 0 in MMSI number indicates the coast station.

Next number ranges from 2-7. This system does not employ use of digit ‘1’. The digits 2-7 denote the specific regions while the last two digits are reserved for national and regional identity respectively.

Some other ship numbers include Naval Registry Identification Number and European Vessel Identification Number.


You may also like to read-What is Maritime Mobile Service Identity?






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