Maritime Mobile Service Identity

Why do I need a MMSI?

The GMDSS is a set of digital signaling protocols used for both routine and distress hailing. The MMSI is key to enhanced emergency message traffic possible with GMDSS.

Digital distress calls contain the MMSI, latitude, longitude, and time of fix. This way, rescue authorities know

  • who you are
  • where you are
  • when you are there.

This saves valuable time in validating the emergency and deploying search and rescue assets. High seas rescues that used to take days now take hours or even minutes thanks to this system.

If you have VHF-DSC, the MMSI is used for routine hailing. Automated hailing offers many benefits such as automatic negotiation of working channels, group hailing, and reduced congestion on calling channels.

AIS data contain your MMSI and certain other fix, course, and speed data to identify your vessel to all others in the local AIS coverage area. In these instances, your personal record information is not used, just your MMSI number.

The information you provide upon registration is used to identify your vessel and its characteristics if you call for emergency assistance. These data reside on a secure site maintained by USPS, and within the Operations Systems Center of the United States Coast Guard. Individual record data are never released nor used for any other purpose.