GPS and AIS: the electronic navigation carriage rules

What the rule requires

AIS is where the thresholds are, so it is where the questions are.

The five AIS Class A triggers

Each of these stands alone. Meet any one and the vessel must have on board a properly installed, operational Coast Guard type-approved AIS Class A device 33 CFR §164.46:

self-propelled, 65 feet or more in length, engaged in commercial service
a towing vessel 26 feet or more in length and more than 600 horsepower, engaged in commercial service
self-propelled and certificated to carry more than 150 passengers
self-propelled and engaged in dredging operations in or near a commercial channel or shipping fairway in a manner likely to restrict or affect the navigation of other vessels
self-propelled and engaged in the movement of certain dangerous cargo as defined in 33 CFR part 160 subpart C, or of flammable or combustible liquid cargo in bulk listed in 46 CFR 30.25-1, Table 30.25-1

Two triggers are dimensional, one turns on the passenger certificate, and two turn on what the vessel is doing at the time. The towing trigger is the one candidates misread: length and horsepower, both, not either.

On the international side, a vessel of 300 gross tonnage or more on an international voyage, and a vessel of 150 gross tonnage or more carrying more than 12 passengers on an international voyage, must comply with the applicable SOLAS Chapter V provisions for a positioning system, AIS Class A, and a transmitting heading device or gyro compass.

Where the AIS rule sits matters for a 100 GT candidate. Part 164 as a whole applies to self-propelled vessels of 1600 or more gross tons on U.S. navigable waters, with the towing-vessel sections §164.70 through §164.82 reaching towing vessels of 12 meters (39.4 feet) or more 33 CFR §164.01. The AIS section is the deliberate exception: it applies to some self-propelled vessels of less than 1600 gross tonnage, which is how a 68-foot commercial vessel comes to owe a Class A device while owing nothing under §164.35.

A 70-foot uninspected passenger vessel carrying six paying passengers on a half-day charter. AIS?

Yes — Class A, unless she qualifies for the Class B substitution. She is self-propelled, 65 feet or more, and engaged in commercial service, which is the first trigger under . Passenger count is irrelevant to that trigger; the 150-passenger figure is a separate, independent trigger, not a filter on the first one.

What AIS transmits, and when it must be transmitting

AIS provides the vessel's identity, type, position, course, speed, navigational status and other safety-related information automatically to appropriately equipped shore stations, other ships and aircraft; it receives the same automatically from similarly fitted ships, monitors and tracks them, and exchanges data with shore-based facilities.

The regulation does not set a report interval for the candidate to memorise. What it regulates is continuity. For the vessels caught by the carriage paragraphs, AIS and its associated devices — positioning system, gyro, converters, displays — must be in continual operation at all times while the vessel is underway or at anchor, and, if moored, at least 15 minutes prior to getting underway. The single exception is when operation would compromise the safety or security of the vessel or a security incident is imminent; the AIS is returned to continuous operation as soon as that has passed, and the time and reason for the silent period should be recorded in the official log and reported to the nearest Captain of the Port or Vessel Traffic Center.

Effective operating condition also means the ability to reinitialize the AIS — which requires access to and knowledge of the power source and password — the ability to access AIS information from the primary conning position, accurate broadcast of a properly assigned MMSI number, and accurate input and upkeep of all data fields.

Three limits on how the set is used, all in the same section. Safety-related text messaging must be in English and solely for pertinent navigation safety information, analogous to a SECURITE broadcast; it is not prohibited for distress but should not be relied on as the primary means of broadcasting MAYDAY or PAN PAN. Application-specific messaging is confined to IMO-adopted or IALA-listed applications for use in the United States or Canada, and to no more than one ASM per minute. And carrying AIS relieves the vessel of nothing: whistle signals, lights and shapes under the 72 COLREGS or the Inland Navigation Rules, and the radio requirements of the Vessel Bridge-to-Bridge Radiotelephone Act, all stand unchanged.

Watchkeeping sits with the Master or person in charge, or the person they designate to pilot or direct the vessel's movement, who must maintain a periodic watch for AIS information.

Each vessel calling at a port in the continental United States, including Alaska south of Cape Prince of Wales, must have a satellite navigation receiver with automatic acquisition of satellite signals after initial operator settings have been entered, and position updates derived from satellite information during each usable satellite pass 33 CFR §164.41. Excepted are vessels owned or bareboat chartered and operated by the United States, a state or its political subdivision, or a foreign nation, and not engaged in commerce.

Read the acquisition spec exactly. It is automatic acquisition after the operator has entered initial settings, not acquisition with no operator input at all. Distractors are built on that difference.

A towing vessel picks up the same requirement by cross-reference, but only on one route: an electronic position-fixing device, a satellite navigational system such as GPS as required by §164.41, is required if the vessel engages in towing seaward of the navigable waters of the U.S. or more than three nautical miles from shore on the Great Lakes 33 CFR §164.72. A towing vessel working exclusively on Western Rivers owes no electronic position-fixing device, and no echo depth-sounding device either.

Using the fix

Electronic and other navigational equipment, external fixed aids to navigation, geographic reference points and hydrographic contours are all to be used when fixing the vessel's position, and the position at each fix is plotted on a chart of the area with the person directing the movement of the vessel informed of it 33 CFR §164.11. Buoys alone may not be used to fix a position. They may corroborate a fix obtained by other means, and where no other aids are available they may be used to establish an estimated position — nothing stronger, because current, heavy seas, ice and collision move them off station.

When the box quits

If the AIS, radar, radio navigation receivers, gyrocompass, echo depth sounding device or primary steering gear stops operating properly, the person directing the movement of the vessel must report it, or cause it to be reported, to the nearest Captain of the Port, District Commander, or the Vessel Traffic Center if participating in a VTS, as soon as possible 33 CFR §164.53. The vessel may continue to the next port of call, subject to the directions of the District Commander or Captain of the Port.

Telling it apart

Class A against Class B

The criterion is not vessel size. It is whether the vessel appears on the closed substitution list, and every entry on that list is gated by one condition: the vessel is not subject to pilotage by other than the vessel Master or crew 33 CFR §164.46.

Fishing industry vessels — on the list outright, which includes fishing vessels, fish processing vessels and fish tender vessels as defined in 46 U.S.C. 2101.
65-foot-and-over commercial vessels — eligible only if certificated to carry fewer than 150 passengers, and not operating in a VTS or VMRS area defined in Table 161.12(c), and not operating at speeds in excess of 14 knots. All three, plus the pilotage gate.
Dredges — a self-propelled vessel engaged in dredging operations may use Class B.
Everyone else caught by a carriage trigger — Class A. There is no general "small vessel" allowance.

Which position-fixing rule governs

The trigger is the route or the trade, and the four rules do not overlap.

Calling at a continental U.S. port (including Alaska south of Cape Prince of Wales) — satellite navigation receiver to the §164.41 specification.
Towing seaward of navigable waters, or more than 3 NM from shore on the Great Lakes — electronic position-fixing device such as GPS, per §164.72(a)(6).
Small passenger vessel on an oceans route — an electronic position fixing device capable of accurate fixes for the area of operation, to the satisfaction of the cognizant OCMI 46 CFR §184.410.
Commercial fishing industry vessel of 79 feet (24 meters) or more — an electronic position fixing device capable of accurate fixes for the area of operation 46 CFR §28.260.

The three kinds of AIS AtoN

An aid to navigation may be enhanced by AIS, broadcasting autonomously and at fixed intervals the name, position, dimensions, type, characteristics and status of the aid 33 CFR §62.52. The criterion separating the three is where the transmitter is, and whether the aid physically exists.

Physical — the AIS unit is fitted to the aid itself.
Synthetic — the aid exists, but the AIS unit is fitted somewhere other than on it.
Virtual — no physical aid exists at all; it is portrayed only on AIS-capable displays.

AIS AtoN also carries laterally significant information such as a port hand mark, and non-lateral marine safety information including environmental data, tidal information and navigation warnings.

Working a question

A 78-foot inspected passenger vessel, certificated for 90 passengers, works a fixed run outside any VTS or VMRS area at a service speed of 12 knots with a maximum of 13. No pilot other than the Master and crew. What AIS device satisfies §164.46?

Test the carriage triggers first. Self-propelled, 65 feet or more, commercial service. Caught. The default answer is now Class A, and every remaining step is about whether a substitution is permitted.
Do not stop at the passenger trigger. She is certificated for 90, so the "more than 150 passengers" trigger is not met — irrelevant, because step 1 already caught her. Candidates who work the list looking for the trigger that fits best rather than the first one that fits get this backwards.
Check the pilotage gate on the whole substitution paragraph. Not subject to pilotage by other than the Master or crew. Passes. Had a state pilot been required, the analysis ends here and the answer is Class A.
Check all three conditions on her substitution entry. Fewer than 150 passengers certificated: 90, passes. Outside a VTS or VMRS area in Table 161.12(c): passes. Not in excess of 14 knots: 13 maximum, passes.
Answer: a Class B device is permissible in lieu of Class A. Move any one input and it reverts — reroute her through a VTS area, uprate her to 16 knots, or increase her certificate past 150, and she owes Class A.
The operating duties are the same either way. Continual operation underway and at anchor, running 15 minutes before getting underway from a mooring, accessible from the primary conning position, accurate MMSI. If her Class B device has no display, she may seek a deviation under §164.55 from the display-access and watchkeeping paragraphs — up to five years, and only by request.

Where candidates lose the point

Applying 65 feet to a towboat. The towing trigger is 26 feet or more and more than 600 horsepower. A 40-foot, 800-horsepower commercial towing vessel is caught; a candidate carrying "65 feet" as the single AIS number answers that she is exempt.

Reading "commercial service" out of the length trigger. A 90-foot private yacht is not caught by the 65-foot trigger. Length alone decides nothing.

Treating Class B as a general small-vessel option. The substitution list is closed and every entry is conditioned. A 70-foot commercial vessel that transits a VTS area, or makes 16 knots, owes Class A regardless of how small she is.

Securing the AIS at anchor. The requirement is continual operation while underway or at anchor, which is the half of the sentence that gets dropped. Anchored overnight with the set off is a violation, and the only lawful shutdown is the safety-or-security silent period, logged and reported.

Thinking AIS discharges another duty. It does not relieve the vessel of whistle signals, of lights or shapes under the COLREGS or Inland Rules, or of the bridge-to-bridge radiotelephone requirements. An option offering AIS as a substitute for any of these is wrong on its face.

Overstating the GPS acquisition spec. The receiver must acquire satellite signals automatically after initial operator settings have been entered. An option promising acquisition with no operator input misstates it.

Fixing on the GPS-and-buoys picture. Buoys alone cannot fix a position; with no other aids available they establish an estimated position only. The plotted fix is still required at each fix, and the person directing the vessel's movement must be told of it.

Heading for port when a box fails. The rule permits continuing to the next port of call, subject to the directions of the District Commander or Captain of the Port. What is mandatory is the report, as soon as possible.

Check yourself

Your 34-foot towing vessel, 700 horsepower, works a commercial harbour towing job on U.S. navigable waters. Class A AIS?

Yes. She is 26 feet or more and more than 600 horsepower, engaged in commercial service, which is a Class A trigger under 33 CFR §164.46. She is not on the Class B substitution list. Watch for a separate exemption question, though: a towing vessel used solely within a limited geographic area for restricted service such as making up or breaking up larger tows is exempt from the §164.72 equipment requirements, not from AIS 33 CFR §164.01.

You are moored at 0730 with a 0800 departure. When must the AIS be switched on?

By 0745 — at least 15 minutes prior to getting underway. Once you are underway or at anchor, the requirement is continual operation.

A vessel calling at a continental U.S. port. What two features must her satellite navigation receiver have?

Automatic acquisition of satellite signals after initial operator settings have been entered, and position updates derived from satellite information during each usable satellite pass 33 CFR §164.41.

Your GPS shows a good fix and two lighted buoys are in sight abeam. Which may you use to fix the position?

Electronic equipment, fixed aids, geographic reference points and hydrographic contours may all be used; buoys alone may not fix a position 33 CFR §164.11. Fix by GPS and any fixed aids available, plot it, and treat the buoys as corroboration.

A symbol appears on your AIS display marking a wreck, but nothing is in the water at that position. What is it?

A virtual AIS AtoN — physically nonexistent, but capable of being portrayed on AIS-capable displays 33 CFR §62.52. Had a buoy been there with the transmitter ashore, it would be synthetic.

Underway on a coastwise transit, your gyrocompass fails. What are you required to do?

Report it, or cause it to be reported, to the nearest Captain of the Port, District Commander, or the Vessel Traffic Center if participating in a VTS, as soon as possible 33 CFR §164.53. You may continue to the next port of call, subject to their direction. The same applies to failure of the AIS, radar, radio navigation receivers, echo depth sounder or primary steering gear.

An inbound vessel is not answering Channel 13. May you raise her by AIS text message instead?

AIS safety-related text messaging is permitted, in English, solely to exchange pertinent navigation safety information, analogous to a SECURITE broadcast . It does not discharge the bridge-to-bridge radiotelephone obligation, and it must not be relied on as the primary means for distress or urgent traffic. Keep working the designated frequency, on which only information necessary for the safe navigation of vessels, or necessary tests, may be transmitted 33 CFR §26.04.