On the Job

What Crew Should Understand about AIS

10 August 2023 By Ted Morley
Marine Traffic
Photo: Courtesy of IBM

Capt. Ted Morley was raised aboard a schooner and has made a career working on board vessels ranging from superyachts to super tankers. During his tenure at sea, he worked his way up from seaman to master. He currently holds a USCG Master’s License, Unlimited Tonnage as well as several foreign certificates. Capt. Morley actively participates in maritime advisory committees in the U.S. as well as overseas and is involved in regulatory policy review in the U.S.. 

There has been some confusion over AIS, what it does, who needs it, and how it works. The automatic identification system (AIS) is an automatic tracking system with transceivers fitted on board vessels that transmit and receive data. Shoreside facilities may only have a receiver so that they can view nearby traffic in local areas. AIS can be used both to augment the shoreside VTS (vessel traffic system) awareness of where vessels are and to provide information to another vessel’s watchstander. The International Maritime Organization (IMO) SOLAS Convention requires AIS to be fitted on board vessels of 300GT or more that are on international voyages, as well as on all passenger vessels, regardless of size. There are also two AIS classes: Class A systems fulfill the mandatory requirements set forth in SOLAS, while the Class B units are intended for non-SOLAS craft, typically smaller recreational vessels.

So how does it work? The AIS requires a dedicated AIS transceiver that operates on VHF radio waves, and the information can be displayed on a dedicated screen or integrated onto a multi-function display or VHF radio display. It’s intended to allow more precise information and a higher information level on vessels operating near each other. Rather than simply seeing a target on the radar or visually, the AIS allows a vessel’s crew to know exactly what ship they’re looking at, which can be a huge help when trying to communicate in congested waters.

Typically, an AIS unit will show nearby vessels within 10 to 20 nautical miles. AIS data is divided into three categories: static data, which provides information about the ship’s characteristics; dynamic data, such as speed and direction; and current voyage-related data. Imagine a shipboard radar or multi-function display that has a symbol for every large vessel within VHF range with speed and heading information for each. By hovering over an AIS icon, you can learn the vessel’s name, its course and speed, classification or vessel type, call sign, registration number, MMSI, and other information such as closest point of approach (CPA) and time to the closest point of approach (TCPA).

AIS broadcasts an update every two to 10 seconds, so the information gained from it is usually much more accurate and up to date than other sources. But beware — not every vessel will be broadcasting, and it is possible to spoof an AIS transmission. AIS use does not replace radar/ARPA use or a lookout. It’s also important to understand that vessels may turn off AIS, thereby negating any potential information gain. AIS works around the world with estimates of nearly half a million devices broadcasting. These broadcasts are picked up by other vessels, shore stations, and even satellites to provide coverage across virtually all areas of the ocean.

So, what happens if the vessel turns AIS off? Well, first we need to look at the legal question there, and that depends on the why — why did the master turn off the AIS? Countries around the world have strict AIS use regulations. The IMO Revised Guidelines for the Onboard Operational Use of Shipborne AIS – A.1106(29) 22 states: “AIS should always be in operation when ships are underway or at anchor. If the master believes that continual AIS operation might compromise the ship’s safety or security or if security incidents are imminent, AIS may be switched off. Unless it would further compromise safety or security, if the ship is operating in a mandatory ship reporting system, the master should report this action and its reason to the competent authority.”

Beware — not every vessel will be broadcasting, and it is possible to spoof an AIS transmission. AIS use does not replace radar/ARPA use or a lookout.

The USCG recently issued its own clarification: The regulation (33 CFR 164.46) in part states that all self-propelled vessels, at a length of 65 feet (20 meters) or more, engaged in commercial service and operating on the territorial seas (within 12 nautical miles of shore) must maintain AIS in effective operating condition, which includes the continual operation of AIS and its associated devices (e.g., positioning system, gyro, converters, displays) at all times while the vessel is underway or at anchor, and, if moored, at least 15 minutes prior to getting underway.

There have been recent reports of stiff fines for vessels that have turned off AIS in regulated areas — the USCG fined a commercial vessel more than US$41,000 for turning off its system near the Columbia River, and in Spain, two fishing vessels were each fined €20,000 for repeatedly turning their systems off for no cause.

Obviously, it’s difficult to know if a vessel has turned their system off unless you’re tracking or monitoring that vessel. Global tensions, black-market transfer of cargo and oil products, as well as vessels looking to evade sanctions or tracking, have all contributed to a recent uptick in cessation of AIS broadcasting.

Regardless of bad actors, the majority of shipping and vessels properly employ the AIS and see the tremendous benefit it provides. Now, with the increased deployment of satellite-based AIS detection systems over the past decade, it’s possible to track vessels across oceans from operation centers ashore and for vessels to look ahead at ports to study congestion and traffic patterns long before arriving. As with any onboard system, proper maintenance, training, and familiarity is crucial to get the most benefit from it.

This article was originally published in the May 2023 issue of Dockwalk.


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