The Triton


More signals clog AIS navigation screens onboard


It is 6:20 in the morning as Capt. Claude Strickland unties the 100-foot private yacht he runs to leave Port Everglades in Ft. Lauderdale. There is only one other vessel underway, a 160-footer.

The yacht’s GPS, radar and electronic navigation charts are on, but the captain cannot see a clear course on the screen. His charts include an AIS (Automatic Identification System) overlay and the display is clogged with symbols representing more than 20 vessels nearby.

The international AIS system is becoming more congested and captains can expect this trend to continue in some heavily traveled areas. Increased requirements, more boaters using it and expansion of AIS uses are a few of the factors that contribute to such congestion.

Capt. Strickland does a security check before leaving the dock to see ahead on his course. But on this morning, instead of waterways, his 15-inch monitor shows yachts and commercial vessels at nearby docks. Not one was underway.

“I couldn’t zoom too far out,” he said. “The yacht name beside each icon blocked out the course, they overlapped. All of those lit areas had no boat moving.”

AIS is a navigation safety communication system designed to provide automatic vessel information for ships about other ships and for coastal authorities.

The device is fundamentally a VHF-FM transceiver with a companion GPS antenna input according to Mark Theissen, vice president at Telemar Yachting in Ft. Lauderdale. The primary types are Class A and B; A is a commercial version that receives and transmits, B is the non-commercial version and there is a receiver-only option. Both relay a combination of data input by the user as well as vessel information, and the classes vary in power and frequency of transmissions. Data input by the yacht includes the ship’s MMSI (an official nine-digit Maritime Mobile Service Identity) and can include type, position, course, speed, navigational status and other safety-related information.

Active AIS vessel icons blot out navigation areas from Port Everglades, Ft. Lauderdale north up the ICW on an overlay of electronic nautical charts. PHOTO/CAPT. BRIAN MITCHELL

Active AIS vessel icons blot out navigation areas from Port Everglades, Ft. Lauderdale north up the ICW on an overlay of electronic nautical charts. PHOTO/CAPT. BRIAN MITCHELL

Class A is basically required on larger vessels. It broadcasts more information more frequently, every 2 to 10 seconds while underway and every 3 minutes while at anchor. Class B broadcasts every 30 seconds if traveling in excess of 2 knots and every 3 minutes if slower.

AIS was developed in the 1990s and in 2002 the International Maritime Organization (IMO) required it for vessels over 300 tons. But those are not the only boats using it, according to Jim Douglas, sales and service at Voyager Maritime Alliance in Ft. Lauderdale.

“More people are utilizing AIS,” Douglas said. “Even small vessels are buying Class B. It is becoming very popular.”

And more AIS users means more transmissions.

“The signals can be easily overwhelmed,” Douglas said. “That results in message collisions,”  

Navigators can tailor their display by scaling up or down to see more or less coverage. They can filter the types of signals to specify commercial, passenger, navigational aids and more. And larger display screens are an option to help to distinguish signals and data.

“Screens are becoming more congested,” Douglas said. “Commercial vessels, cruise ships have big displays. The bigger displays provide much less clutter as they display much more than just AIS targets.”

But that leaves most users to struggle with a lot of signals on standard screen sizes.

Capt. Strickland navigates waters from the Atlantic to the Pacific and does not rely on his AIS alone. He knows how to look out the window for vessel traffic, but he is a fan.

“It’s a wonderful tool and gives me more information than radar,” Capt. Strickland said. “It’s so easy to put a cursor on nearby vessels so you don’t have to call every boat.”

He gave an example of how he uses AIS to enter Port Everglades from offshore. He starts with a 22-mile scale which shows 11 miles each side of his yacht’s location. As he gets closer to port, he scales down.

“But once into port, and cleared in, when we make the turn north, that’s when I want to be able to see a mile or two to see the trip to Bahia Mar,” Capt. Strickland said. “But you can’t because AIS is on all the boats at the dock.”

“I have to scale down to 700 yards to keep from being blocked out,” Strickland said.

“Being able to see and understand the speeds and courses of other traffic on the high seas is very important,” he said. “And just as important is the ability to see this information from other vessels while I’m in channels, ports and other confined waterways.

“Ft. Lauderdale is a simple port, but when it’s a new area, it’s more of an issue,” he said.

Capts. Brian and Sue Mitchell monitor their AIS especially from Asia to Italy recently. But they run into the same issue in some areas at certain times.

“It’s gotten so you have to turn the AIS off to navigate, to clearly see in a high-traffic area such as Monaco, St. Tropez, Antibes, Ft. Lauderdale, West Palm Beach and other places of high traffic where you get real congregations,” Capt. Brian Mitchell said. “Although a month ago it was looking way worse, as there were more yachts in the Ft. Lauderdale area in April and May.”

Requirements are laid out in SOLAS (International Convention for the Safety of Life at Sea) according to vessel type. Specific details for IMO carriage requirement for AIS include all ships of 300 gross tons on international voyages and vessel of 150 gt or more, when carrying more than 12 passengers on an international voyage, to comply by the rules that went into effect in 2004.

And the AIS is to remain active as the regulations state, “AIS should always be in operation when ships are underway or at anchor. If the master believes that the continual operation of AIS might compromise the safety or security of his/her ship or where security incidents are imminent, the AIS may be switched off.”

The U.S. Coast Guard agreed and expanded carriage requirements as of Jan. 30, 2015 which went into effect on April 7 of this year. This implemented the AIS requirements of SOLAS and the U.S. Maritime Transportation Security Act and includes most commercial vessels operating on U.S. navigable waters defined as 65 feet or more in length, towing vessels of 26 feet or more and vessels certified to carry more than 150 passengers. Some fishing vessels use Class B.

Active AIS vessel icons blot out navigation areas from Port Everglades, Ft. Lauderdale north up the ICW on an overlay of electronic nautical charts. PHOTO by CAPT. CLAUDE STRICKLAND

Active AIS vessel icons blot out navigation areas from Port Everglades, Ft. Lauderdale north up the ICW on an overlay of electronic nautical charts. PHOTO by CAPT. CLAUDE STRICKLAND

When to use AIS in the United States is described in Code of Federal Regulations (CFR 33) as, “…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; except when its operation would compromise the safety or security of the vessel or a security incident is imminent. The AIS should be returned to continuous operation as soon as the compromise has been mitigated or the security incident has passed. The time and reason for the silent period should be recorded in the ship’s official log and reported to the nearest Captain of the Port or Vessel Traffic Center (VTC).”

Aside from use onboard, AIS has expanded from the primary use on vessels to include a variety of terrestrial uses.

The USCG and U.S. Department of Homeland Security have implemented the Nationwide Automatic Identification System (NAIS). According to their website NAIS facilities have been installed in more than 60 major ports and coastal areas. The first phase of the system receives AIS messages but the second has transceiver capabilities to transmit data out to 24 nautical miles and receive data from out to 50 nautical miles. As of last year, the system received more than 92 million AIS messages per day from more than 12,700 unique vessels.

There are AIS on navigational aids that do not physically exist. Called virtual buoys, electronic aids to navigation (eATON) are being transmitted to vessels through the NAIS.

And there are even AIS signals on navigational aids. British Admiralty (BA) chart annotator Francisco Sheuat

occasionally adds the symbol to the BA nautical charts he hand-corrects at Bluewater Books and Charts in Ft. Lauderdale.

“Sometimes AIS is added to radar beacons, described as RACON on the charts, on the fixed navigation marks,” Sheuat said.

British Admiralty chart annotator Francisco Sheuat hand-corrects a nautical chart to add an AIS symbol onto an aid to navigation. PHOTO BY DORIE COX

British Admiralty chart annotator Francisco Sheuat hand-corrects a nautical chart to add an AIS symbol onto an aid to navigation. PHOTO BY DORIE COX

Requirements for AIS come from the top down. The IMO is the big one and flag states require yachts to follow international law first.

Flag states also require yachts to follow regulations in the local waters of navigation. Sometimes these may be above or beyond international rules, but wherever a yacht is, each country could have its own requirements.

Yacht insurers similarly follow international and flag state regulations, said Nancy Poppe, North American yacht practice leader with Willis Marine Superyachts.

“Our experience with AIS is with vessels over 300 gross tons. If the boat is required by IMO or flag state to have one, the insurers expect them to,” Poppe said.

The AIS was designed for safety and that is what Capt. Strickland wants to use it for.

“It’s important to see what is maneuvering, what size, where’s it going; that’s what you’re looking to see,” Capt. Strickland said.

“Most ships need a mile to clear and that’s what I don’t want blotted out,” he said. “Because no matter the rules, at sea, the law of tonnage still wins.”

Dorie Cox is associate editor of The Triton. Comments on this story are welcome at

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About Dorie Cox

Dorie Cox is editor of The Triton.

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3 thoughts on “More signals clog AIS navigation screens onboard

  1. Dave

    Most current navigation software allows you to turn off labels as an option. If you need to know vessel data, then you either hover over or click on the vessel. If your software does not allow this, then it is time to update it. Otherwise read the manual and find out where the settings for vessel labels are. I run through the same area and have no issues with the number of AIS targets.

  2. Jon

    It seems like this is an issue of bad digital cartography and filtering of AIS targets. I’ve found AIS to be MORE useful when a smaller boat has it that a 300 ton ship and would encourage anyone to put it on their vessel. The small boat has a much less predictable path and is harder to see its exact heading at a distance than a large ship. AIS makes this very apparent.

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