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What is the 7 digit MMSI?

Published in Maritime Identification 2 mins read

A 7-digit Maritime Mobile Service Identity (MMSI) is a unique identification number assigned to ship stations, coast stations, coast earth stations, and group calls. This number remains with the vessel for its entire lifespan, irrespective of changes in name, ownership, or flag.

Importance of MMSI

The MMSI is crucial for maritime communications and safety. It serves as a digital "fingerprint" for a vessel, enabling:

  • Identification: Allows authorities and other vessels to quickly and accurately identify a specific ship.
  • Distress Alerting: Essential for transmitting distress calls and receiving assistance during emergencies.
  • Automated Information: Enables automated exchange of information, such as position, speed, and course, using systems like Automatic Identification System (AIS) and Digital Selective Calling (DSC).
  • Tracking: Facilitates tracking and monitoring of vessels by maritime authorities and fleet managers.

MMSI Structure and Allocation

While the overall MMSI is 9 digits, the question specifically asks about the 7-digit portion. The first three digits of an MMSI indicate the country of registration (Maritime Identification Digits or MID). The remaining six digits are assigned by the responsible national authority. When only referring to the ship's specific ID (excluding the MID), the relevant portion is 7 digits long. This 7-digit portion comprises the final two digits of the MID and the five subsequent digits assigned to that particular vessel. The final two digits of the MID are included in the seven-digit figure to ensure uniqueness, due to the potential for multiple countries to assign similar numbers. This ensures globally unique identification.

Example

Let's say a vessel's full 9-digit MMSI is 234567890. In this example:

  • 234 would be the Maritime Identification Digits (MID) representing a specific country (e.g., United Kingdom).
  • 567890 is the unique number assigned by that country to the vessel.

When communicating about the ship's unique ID, excluding the general country identifier, one could refer to the 7-digit portion, 3456789.

Conclusion

The 7-digit MMSI represents the unique portion of a vessel's identification number, excluding the most significant digit of the MID, and is essential for accurate identification and communication in maritime operations.

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