Rogue AIS units


Along with GPS, one of the biggest advances in marine electronics has been the automatic identification system (AIS), which has made collision avoidance a much easier proposition. Now, according to the recent advisory released by the FCC and the Coast Guard, it appears that the great utility and wide acceptance of AIS has apparently resulted in the marketing of some substandard units that don’t transmit correct AIS info.

The Coast Guard wrote in a press release that “AIS equipment that is noncompliant with adopted international standards can confuse, degrade or even disrupt other users’ systems.” This subject is important for voyagers, of course, because ocean voyagers having to deal with confusing or noncompliant signals might increase the chances of a collision instead of lowering them as AIS was designed to do.

“In the last year, the Coast Guard has received various reports from perplexed AIS users who have seen various unknown and erratic targets appearing on their AIS,” said Jorge Arroyo, an AIS expert from the Coast Guard’s Navigation Technology and Risk Management Division. “Many of which were unable to be ‘seen’ on radar or visually.”

When many of these noncompliant AIS returns were further studied, according to Arroyo, they appeared to come from AIS-like devices used to mark fish nets, yet they appeared as vessels.

“This is contrary to FCC and USCG regulations; such noncompliant devices, amongst other things, are illegal to be sold, purchased or used in the U.S.,” said Arroyo. “AIS is required to be properly installed, maintained and used, but foremost, you should ensure you are buying a true AIS and not a knock-off sold on the Internet. As with all purchases, buyers beware — be informed.”

The determination of what frequencies are acceptable for various devices to use is a complex one that flows through several organizations and authorities. The primary international organization responsible for frequency allocation is the International Telecommunication Union (ITU). This specialized UN agency based in Geneva, Switzerland, coordinates the worldwide allocation of frequencies in the electromagnetic spectrum. Once the ITU has reached agreement on how different frequencies on the spectrum are assigned to various uses, then it falls to national authorities — like the FCC in the U.S., for example — to set rules about frequency use. Other U.S. authorities are involved as well. In the marine world, those include the U.S. Coast Guard and advisory groups like the Radio Technical Commission for Maritime (RTCM).

When it comes to AIS, the VHF frequencies allocated by the ITU and authorized by the FCC are 156.775 MHz, 156.825 MHz, 161.975 MHz or 162.025 MHz. And the only devices authorized to use these frequencies are: Class A and Class B ship borne equipment, AIS Search and Rescue Transmitters, and Maritime Survivor Locating Devices.

The impressive way that AIS works without any outside control is what gives the system its “automatic” name and allows users to use the system “hands-free.” AIS-equipped VHF radios follow an ingenious transmission/time slot allocation protocol that is self-regulating, but which requires that participating units follow the rules so all the AIS units in a geographic area can be heard.

Yet some unscrupulous providers are making and marketing radio transmitters operating at AIS frequencies. One common use for these units, as noted above, is for attaching to fishing nets to determine their location, presumably for tracking and retrieving them. These noncompliant devices can be purchased via the Internet.

What makes this more confusing is that there are already frequencies allocated for use by net tracking devices. According to the FCC, “Compliant maritime equipment intended for tracking fishing nets is authorized to operate in the 1900-2000 kHz band, not the AIS frequencies. These devices will not be advertised as AIS equipment.” But equipment using these frequencies is generally for homing use only and doesn’t have the interactive nature of AIS-type devices. It’s the interactive and automatic nature of AIS that apparently makes it an attractive market for rogue manufacturers to offer these noncompliant units.

Arroyo wrote in an email that these noncompliant devices have also been found throughout the AIS product lineup. “The fish net markers are the most pervasive [type of noncompliant device], but we’ve also encountered other non-certified devices being marketed and sold as AIS Class A, Class B, AIS AtoN units, etc.”

When asked how these noncompliant units behave at sea, Arroyo wrote: “Most of the fish net markers show up as a vessel but, if that wasn’t bad enough, many of them transmit randomly, which defeats the self-organized behavior of an AIS network (see “How AIS Works”), which can interfere with other users in the area.”

According to a recent USCG press release, violators of the FCC’s rule may be subject to penalties authorized by the Communications Act, including but not limited to substantial monetary fines of up to $19,639 per day for marketing violations and up to $147,290 for an ongoing violation.

By Ocean Navigator