AIS and MMSI for vessel tracking

What is AIS and how does it work? What is the link between AIS and MMSI?

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AIS stands for Automatic Identification System. MMSI stands for Maritime Mobile Service Identities.

In basic terms, you can think of AIS as a GPS or a location-sharing system for vessels and MMSI as the unique identifier of a vessel in that system.

If we get a bit more technical, IMO mandates vessels bigger than 500GT and vessels bigger than 300GT are equipped with an AIS transponder. They transmit data such as their position, heading, and speed through these transponders. These signals are then collected by receivers on land or satellite and processed into useful information.

AIS was primarily introduced for maritime safety and security but most vessel monitoring, performance, and analytics systems have been built around this ecosystem as well.

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What is AIS?
AIS stands for Automatic Identification System, and it is a system used in the maritime industry for vessel tracking and identification.

How it works?
The AIS system uses VHF radio signals to transmit and receive data between vessels and shore-based stations. The data transmitted includes the vessel’s identity, position, course, speed, destination and other details.

The AIS system consists of two main components: a transponder on the vessel and a receiver on shore or on other vessels. The transponder on the vessel constantly broadcasts information about the vessel’s position, speed, and other relevant information. This information is received by other vessels, specialized satellites or shore-based stations within range of the signal, allowing them to track the vessel’s movements and to take appropriate action if necessary.

What is the importance of AIS system?
AIS is an important tool for maritime safety and security, as it enables vessels to avoid collisions and to respond quickly to emergency situations. It also helps authorities to monitor and manage vessel traffic, and to detect and prevent illegal activities, such as piracy and smuggling. This is why AIS is mandatory for:

  • All vessels with a gross tonnage of 300 or more engaged in international voyages, including cargo ships, tankers, and passenger vessels.
  • All passenger ships, regardless of size, on domestic voyages.
  • All vessels over 500 gross tonnage, regardless of the type of voyage, that carry hazardous or polluting cargo.
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Originally, AIS was used terrestrially, meaning the signal was sent from the boat to land and had a range of roughly 20 miles (also considering the earth’s curvature). As ships began sailing further away from land, they started sending the signal to low orbit satellites, relaying information back to land. This meant ships could sail as far as they liked, and we’d always have peace of mind knowing exactly where they were and how they were doing.

The AIS system consists of one VHF transmitter, two VHF TDMA receivers, one VHF DSC receiver, and a standard marine electronic communications link to shipboard display and sensor systems. Position and timing information is normally derived from an integral or external GPS receiver. Other information broadcast by the AIS is electronically obtained from shipboard equipment through standard marine data connections.

It’s been really informative learning about AIS and MMSI from all the previous responses. In a nutshell, AIS is a GPS-like system for vessels that uses VHF radio signals to transmit and receive data between vessels and shore-based stations. MMSI serves as the unique identifier of a vessel within the AIS system. The system has evolved over time to include low orbit satellites, allowing for greater coverage and reliability.

With this in mind, I’m curious about how often AIS data is updated and if there’s any delay in the transmission of the data. Additionally, are there any known limitations or issues with AIS that mariners should be aware of? @sinan-ansen @aydin-mammadov @ali-gara @furkan-zblbl

@tural Yes, AIS is can be switched off by the vessel for different reasons. Reported destinations can be wrong for either political reasons or because of an input error by the captain. Also, AIS signals get mixed up by satellite providers around ports where there are A LOT of ships such as Singapore Port so you could potentially get a mixed up signal.