Picture a radar-chartplotter display, with overlaid electronic chart data, that includes an icon for every significant ship within VHF radio range, each with a velocity vector (showing that vessel’s speed and heading). Each ship icon reflects the actual size of the ship, with positions accurate to GPS precision. By “clicking” on a ship mark, you can learn the ship’s name, course and speed, classification, call sign, MMSI, and other information. Maneuvering information, closest point of approach (CPA), time to closest point of approach (TCPA) and other navigation data is also available. Information previously visible only to the Vessel Traffic Service is now available to every AIS-equipped vessel.
The Automatic Identification System is a digital VHF radio-based transponder system that can prevent collisions, and can protect your boat from being run down by a huge, fast moving ship. It’s like digital radar with precise position information. AIS uses GPS, VHF radio and sophisticated digital processing to automatically communicate between vessels without any operator interaction.
The system’s range is similar to that of your VHF radio, essentially depending on the height of the antenna. Its propagation is slightly better than that of radar, due to the longer wavelength, so it’s possible to “see” around bends in rivers or over islands if the landmasses are not too high. AIS information is not degraded by rain-clutter like radar, so it works the same in all weather. The consensus among safety experts is that AIS is extremely valuable, especially if you travel at night or in crowded shipping lanes with restricted visibility.
Class A: Full-function transceivers are required for ships over 300 gross tons that travel internationally, and for passenger ships. More classes of commercial vessels may be added to these requirements soon (see below). Class A AIS units include both transmitters and receivers, and automatically transmit every two to 10 seconds when the ship is under way, and every three minutes when anchored. Transmitting at 20 watts, they consume substantial amounts of electrical power. Class A units are also often pricey; the em-trak A100 (Model 12333944, priced at about $3,000) is a Class A unit.
Class B: This class offers a somewhat reduced set of functions at a much lower cost, and is intended for recreational vessels and others not required to carry Class A AIS. Class B was approved for use throughout the U.S. in September 2008. It is nearly identical to Class A, except that Class B:
Receive-Only: Units like the ICOM MXA5000, Garmin AIS 300 and Raymarine AIS350 are “receive-only,” not two-way transceivers, and let you identify what ships are in the neighborhood while you remain off the AIS grid. Think of a receive-only unit more like radar than a radar unit with radar reflector. These receivers, containing only the two-channel VHF receiver and decoding software, are not Class B, since they aren’t active transmitters on the AIS system.
The Raymarine AIS650 and Garmin’s AIS 600 are true Class B transceivers that offer both send and receive functions. You can also turn the transmit function off and operate in Silent Mode (one AIS authority calls it “Pirate Mode”—your setting of choice when operating your boat in piracy-infested waters). Both of these are “black box” receivers that output AIS data to your compatible chartplotter, PC navigation software, or a dedicated display. ICOM’s MA500TR and Simrad’s AI50 include their own displays.
FCC regulations require that all Class B AIS units have their “static data”, your boat’s MMSI (Maritime Mobile Service Identity) Number and other dimensional and identifying information, programmed by a professional—in this case by trained technicians at our warehouse. If you do not have an MMSI number, you can get one for free at www.boatus.com/mmsi.
If your boating takes you to international ports, you must obtain a Ship Station License and your MMSI number from the FCC. Go to FCC Ship Station Licensing for instructions. Currently there is a fee for this license. If you believe that your vessel may not be a “recreational boat” due to use or size, this site will also provide information defining whether or not you will need a Ship Station License.
When you order an AIS transceiver, collect and submit the following information online at: westmarine.com/ais. Your AIS unit will then be pre-programmed for your boat and shipped to your address.
AIS units like the em-trak B100 can be operated (in Receive Mode only) before the boat’s MMSI number and data are programmed on an SD Card.
Do you have an NMEA 2000 network on your boat? About half of the AIS units in our assortment are compatible with the newest networking protocol, and they’re also backward-compatible with the older NMEA 0183 standard.
Does the AIS unit have special features that only work when networked with same-brand multi-function displays? For example, Garmin’s AIS 600 integrates with a Garmin chartplotter and VHF radio via NMEA 2000, giving you the ability to initiate a call to any MMSI target directly from the chartplotter by selecting the “call with radio” function. Raymarine’s AIS650, when used with Raymarine multi-function displays, supports Raymarine’s Buddy Tracking feature, which allows you to save AIS targets of interest with a special icon and “friendly” name.
A few AIS units include an antenna splitter, allowing it to share an antenna with your VHF radio. Garmin’s AIS 600, AIS 300 and ICOM’s MXA5000 include a built-in splitter. Simrad and en-trac make add-on antenna splitters. Most AIS units include a GPS antenna.
Here’s some information regarding expansion of the types of commercial vessels who must carry an AIS transceiver. When these new rules take effect, recreational boaters will be able to observe AIS info about additional types of vessels.
Currently, the AIS carriage requirement for domestic vessels is largely limited to self-propelled commercial vessels of 65’ or longer that are engaged on an international voyage or operating in a designated VTS area (a busy port with Vessel Traffic Service controls). This will greatly change under the Coast Guard proposal (RIN: 1625-AA99). The VTS area provision will be eliminated, along with the international voyage provision. Also eliminated would be the blanket exemption for fishing vessels.
Under the proposal, which is in the Final Rule Stage of implementation as of January, 2014, the following domestic vessels would be required to have onboard a properly installed, operational, Coast Guard type-approved AIS: