The Automatic Identification System (AIS) – Aiding Maritime Safety

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Image Courtesy: Wikimedia

The Automatic Identification System (AIS) is a digital VHF radio-based transponder system that can prevent collisions as it displays the information of other vessels in the vicinity such as unique identification, position, course and speed. It is capable of handling well over 4,500 reports per minute and updates as often as every two seconds. It uses Self-Organising Time Division Multiple Access (SOTDMA) technology to meet this high broadcast rate and ensure reliable ship-to-ship operation.

This information can:

  • be displayed on a computer or chart plotter or a screen such as ECDIS
  • aid in situational awareness
  • provide a means to assist in collision avoidance.

AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport. However, vessels fitted with AIS transceivers can be tracked by AIS base stations located along coast lines or, when out of range of terrestrial networks, through a growing number of satellites that are fitted with special AIS receivers, which are capable of deconflicting a large number of signatures.

According to the U.S. Coast Guard Navigation Centre (The Navigation Centre of Excellence), “Each ship “symbol” can reflect the actual size of the ship, with position to GPS or differential GPS accuracy. By “clicking” on a ship symbol, you can learn the ship name, course and speed, classification, call sign, registration number, MMSI, and other information. Maneuvering information, closest point of approach (CPA), time to closest point of approach (TCPA) and other navigation information, more accurate and more timely than information available from an automatic radar plotting aid, can also be available. Display information previously available only to modern Vessel Traffic Service operations centres can now be available to every AIS user as seen below.

What You See With AIS
Image Courtesy: The Navigation Centre of Excellence

With this information, you can call any ship over VHF radiotelephone by name, rather than by “ship off my port bow” or some other imprecise means. Or you can dial it up directly using GMDSS equipment. Or you can send to the ship, or receive from it, short safety-related email messages.”

The Australian Maritime Safety Authority states, ” There are two types of shipborne AIS:

  • AIS Class A – AIS Class A has been mandated by the IMO through the Safety of Life at Sea Convention (SOLAS), for:
    • vessels of 300 gross tonnage and upwards engaged on international voyages
    • cargo ships of 500 gross tonnage and upwards not engaged on international voyages
    • passenger ships, irrespective of size, which carry more than 12 passengers.
  • AIS Class B – AIS Class B provides less functionality than an AIS Class A and is intended for non-SOLAS vessels and pleasure craft. 

    The IMO does not mandate for AIS Class B to be installed.

    There are also different types of non-shipborne AIS, including:

    • AIS used for shore stations (AIS Base Stations)
    • AIS Aids to Navigation (AIS AtoN)
    • AIS Search and Rescue Transmitters (AIS SART)
    • AIS fitted to Search and Rescue Aircraft (SAR aircraft)
    • Man Overboard units (AIS MOB).”

The Canadian Coast Guard reveals, “AIS shore infrastructure is integrated within Marine Communication and Traffic Services (MCTS) centres and has resulted in 19 MCTS centres and 113 remote sites fitted with AIS systems.” On how it helps with maritime safety, it states, “In addition to the management of shipping traffic in general, MCTS centres provide an AIS data feed to other Government Departments such as the Department of National Defence, as well as to the Marine Security Operations Centres, to further contribute to maritime domain awareness and assist in the identification of anomalies within Canada’s waters.”

Image Courtesy: The Navigation Centre of Excellence

According to Wikipedia, the functions AIS serves are as follows:

Collision avoidance – AIS was developed by the IMO technical committees as a technology to avoid collisions among large vessels at sea that are not within range of shore-based systems. The technology identifies every vessel individually, along with its specific position and movements, enabling a virtual picture to be created in real time. The AIS standards include a variety of automatic calculations based on these position reports such as Closest Point of Approach (CPA) and collision alarms. As AIS is not used by all vessels, AIS is usually used in conjunction with radar. When a ship is navigating at sea, information about the movement and identity of other ships in the vicinity is critical for navigators to make decisions to avoid collision with other ships and dangers (shoal or rocks). Visual observation (e.g., unaided, binoculars, and night vision), audio exchanges (e.g., whistle, horns, and VHF radio), and radar or Automatic Radar Plotting Aid are historically used for this purpose. These preventative mechanisms, however, sometimes fail due to time delays, radar limitations, miscalculations, and display malfunctions and can result in a collision. While requirements of AIS are to display only very basic text information, the data obtained can be integrated with a graphical electronic chart or a radar display, providing consolidated navigational information on a single display.

Fishing fleet monitoring and control – AIS is widely used by national authorities to track and monitor the activities of their national fishing fleets. AIS enables authorities to reliably and cost effectively monitor fishing vessel activities along their coast line, typically out to a range of 60 miles (depending on location and quality of coast based receivers/base stations) with supplementary data from satellite based networks.
Vessel traffic services – In busy waters and harbours, a local vessel traffic service (VTS) may exist to manage ship traffic. Here, AIS provides additional traffic awareness and information about the configuration and movements of ships.
Maritime security – AIS enables authorities to identify specific vessels and their activity within or near a nation’s Exclusive Economic Zone. When AIS data is fused with existing radar systems, authorities are able to differentiate between vessels more easily. AIS data can be automatically processed to create normalised activity patterns for individual vessels, which when breached, create an alert, thus highlighting potential threats for more efficient use of security assets. AIS improves maritime domain awareness and allows for heightened security and control. Additionally, AIS can be applied to freshwater river systems and lakes.
Aids to navigation – The AIS aids to navigation (AtoN) product standard was developed with the ability to broadcast the positions and names of objects other than vessels, such as navigational aid and marker positions and dynamic data reflecting the marker’s environment (e.g., currents and climatic conditions). These aids can be located on shore, such as in a lighthouse, or on water, platforms, or buoys. The U.S. Coast Guard has suggested that AIS might replace racon (radar beacons) currently used for electronic navigation aids. AtoN’s enable authorities to remotely monitor the status of a buoy, such as the status of the lantern, as well as transmit live data from sensors (such as weather and sea state) located on the buoy back to vessels fitted with AIS transceivers or local authorities. An AtoN will broadcast its position and Identity along with all the other information. The AtoN standard also permits the transmit of ‘Virtual AtoN’ positions whereby a single device may transmit messages with a ‘false’ position such that an AtoN marker appears on electronic charts, although a physical AtoN may not be present at that location.
Search and rescue – For coordinating on-scene resources of a marine search and rescue (SAR) operation, it is imperative to have data on the position and navigation status of other ships in the vicinity. In such cases, AIS can provide additional information and enhance awareness of available resources, even if the AIS range is limited to VHF radio range. The AIS standard also envisioned the possible use on SAR aircraft, and included a message (AIS Message 9) for aircraft to report their position. To aid SAR vessels and aircraft in locating people in distress, the specification (IEC 61097-14 Ed 1.0) for an AIS-based SAR transmitter (AIS-SART) was developed by the IEC’s TC80 AIS work group. AIS-SART was added to Global Maritime Distress Safety System regulations effective January 1, 2010. AIS-SARTs have been available on the market since at least 2009. Recent regulations have mandated the installation of AIS systems on all Safety Of Life At Sea (SOLAS) vessels and vessels over 300 tons.
Accident investigation – AIS information received by VTS is important for accident investigation since it provides accurate historical data on time, identity, GPS-based position, compass heading, course over ground, speed (by log/SOG), and rates of turn, rather than the less accurate information provided by radar. A more complete picture of the events could be obtained by Voyage Data Recorder (VDR) data if available and maintained on board for details of the movement of the ship, voice communication and radar pictures during the accidents. However, VDR data are not maintained due to the limited twelve hours storage by IMO requirement.
Ocean currents estimates – Ocean surface current estimates based on the analysis of AIS data have been available from French company, e-Odyn, since December 2015.:
Infrastructure Protection – AIS information can be used by owners of marine seabed infrastructure, such as cables or pipelines, to monitor the activities of vessels close to their assets in close to real time. This information can then be used to trigger alerts to inform the owner and potentially avoid an incident where damage to the asset might occur.
Fleet and cargo tracking – Internet disseminated AIS can be used by fleet or ship managers to keep track of the global location of their ships. Cargo dispatchers, or the owners of goods in transit can track the progress of cargo and anticipate arrival times in port.

Trend Micro states, “AIS provides a lot of benefits in terms of traffic monitoring and vessel assistance. Ship owners and maritime authorities greatly rely on AIS to supplement information acquired from traditional radars for location tracking and is used to detect and avoid vessel collisions. Since its introduction in 2002, AIS has been installed in 300,000 vessels on a global scale, set up to monitor marine traffic and improve safety. AIS has also been proven to be instrumental in accident investigation and search-and-rescue (SAR) operations.”

In addition to all of the above, the AIS is relatively simple to install and its growing connectivity ensures accurate information. However, it is not foolproof and can be compromised at times through software and RF threats. Care must be taken to ascertain that the latest updates and security measures are in place.

Sea News Feature, February 12