If you have a question about marine AIS, it should be answered here.

If not, please email us and we will be glad to answer your questions.    Email: marketing@acrartex.com

Q:  What is marine AIS? 

A:  Marine AIS or Automatic Identification System  is a maritime navigation safety communications system standardized by the International Telecommunication Union (ITU) and adopted by the International Maritime Organization (IMO). It is a tracking system used on commercial and recreational vessels that allows captains to identify, locate and communicate with other vessels by an electronic data transfer of navigational and vessel information with other AIS equipped vessels nearby.

Q:  How does marine AIS help to increase security (and what is NAIS)? 

A:  Although marine AIS is primarily and foremost a navigation tool for collision avoidance, the Coast Guard believes that the AIS will improve security also. AIS and our Nationwide AIS Project (NAIS) increases the Coast Guard’s awareness of vessels in the maritime domain, especially vessels approaching U.S. ports. The AIS corroborates and provides identification and position of vessels not always possible through voice radio communication or radar alone.

Q:  When must marine AIS be in operation? 

A:  Vessels equipped with AIS (either by mandatory carriage or voluntarily) must abide by the requirements set forth in 33 CFR 164.46(d) and should especially ensure their AIS is in properly installed, using an assigned MMSI, and, that its data is accessible from the primary conning position of the vessel. Also, that it be in 'effective operating condition', which entails the continuous operation of AIS and the accurate input and upkeep of AIS data fields during all times that the vessel is navigating (underway or at anchor), and, at least 15 minutes prior to unmooring. Should continual operation of AIS compromise the safety or security of the vessel or where a security incident is imminent, the AIS may be switched off. This action and the reason for taking it must be reported to the nearest U.S. Captain of the Port or Vessel Traffic Center and recorded in the ship's logbook. The AIS should return to continuous operation as soon as the source of danger has been mitigated.

Q:  Why have some marine AIS units stopped broadcasting valid position reports? 

A:  On February 27th, 2008 the GPS constellation increased to 32 satellites (PRN 32) thus providing a 5% increase in satellite availability and DOP (dilution of precision) world-wide. It has come to our attention that some (non-USCG type approved) AIS units-particularly old equipment which is non-compliant with the GPS interface standard (IS-GPS-200)-cannot recognize this additional satellite and subsequently are unable to calculate a position and broadcast a valid AIS Position Report. Note, the reported malfunctioning units do continue to receive position reports and are able to send and receive AIS text messages. Owners of AIS equipment denoted here, however, should be aware that their internal GPS systems may not act as a proper-timing or position-back-up under certain circumstances, i.e. when in view of PRN32. AIS users must ensure their units have or are interfaced with a properly operating Electronic Position Fixing System at all times. GPS and/or AIS problems should be reported via the NAVCEN website or via phone to the USCG Navigation Information Service at 1-703-313-5900.

Q:  Why am I unable to see an AIS vessels' name or other static information (dimensions, call sign, etc.)? 

A:  Shipboard AIS units autonomously broadcast two different AIS messages: a 'position report' which includes the vessels dynamic data (e.g. latitude, longitude, position accuracy, time, course, speed, navigation status); and, a 'static and voyage related report' which includes data particular to the vessel (e.g. name, dimensions, type) and regarding its voyage (e.g. static draft, destination, and ETA). Position reports are broadcasted very frequently (between 2-10 seconds-depending on the vessels speed-or every 3 minutes if at anchor), while static and voyage related reports are sent every six minutes; thus it is common and likely that an AIS user will receive numerous position reports from a vessel prior to receipt of the vessels' name and type, etc.

Q:  What is a MMSI and where can I get one for my AIS?

A:  A unique and official Maritime Mobile Service Identity (MMSI) number is required for every AIS unit.

Q:  Why do I sometimes see more than one vessel with the same MMSI or vessel name (i.e. NAUT)? 

A:  AIS users are required to operate their unit with a valid MMSI, unfortunately, some users neglect to do so (for example, use: 111111111, 123456789, 00000001, their U.S. documentation number, etc). A valid MMSI will start with a digit from 2 to 7, a U.S. assigned MMSI will start with either 338, 366, 367, 368, or 369. AIS users whom encounter a vessel using MMSI: 1193046 or named: NAUT should notify the user that their AIS unit is broadcasting improper data; see Nauticast AIS-MMSI Technical Bulletin for further information. All AIS users should check the accuracy of their AIS data prior to each voyage, and, particularly units that have been shutdown for any period of time. NOTE: If you are receiving (in range of) AIS reports from vessels using the same MMSI, they will appear as one vessel (jumping from position-to-position or line-to-line) on a graphical screen (e.g. ECS, ECDIS, radar) or on the AIS Minimal Keyboard Device (MKD).

Q:  I just purchased and installed a marine AIS Class B transceiver, will AIS Class A users ‘see’ me? 

A:  Although all Class A devices will receive Class B information; unfortunately, some older Class A models are unable to display this information on their Minimum Keyboard and Display (MKD) or may only have available the Class B vessel’s dynamic data (i.e. position, course and speed) but not its static data (i.e. vessel name, call-sign). Therefore, the Coast Guard cautions new AIS Class B users to not assume that they are being ‘seen’ by all other AIS users or that all their information is available to all Class A users. Further, we exhort users of certain AIS Class A units to, as soon as practicable, update their MKD’s and/or other external navigation display systems (e.g. Electronic Charts Systems, Electronic Chart & Display Information Systems, radar, etc.) in order to view this new stream of valuable AIS information that will enhance navigation safety and mitigate the risk of collision. A rulemaking to mandate such an update is forthcoming. Here is a listing of Coast Guard type-approved AIS Class A units which require a firmware update in order to display AIS Class B information.

Q:  Where can I get marine AIS data? 

A:  Although the U.S. Coast Guard operates our Nation's AIS network (NAIS), we do not --currently-- make our AIS information available to the general public. There are, however, numerous AIS networks and commercial purveyors that do provide AIS data and track information on the World Wide Web; many of which are listed on Wikipedia's AIS webpage. Local, state and federal government agencies may request U.S. Coast Guard Nation-wide AIS data here.

Q:  What is AIS Channel Management? 

A:  One of the lesser known and potent features of AIS is its ability to operate on multiple channels of the VHF-FM marine band. This frequency agility ensures AIS can be used even when the default channels are otherwise unavailable or compromised. In such conditions, competent authorities, such as the Coast Guard, can use an AIS base station to tele-command shipborne AIS devices to other more appropriate channels when within a defined region(s) of 200 to 2000 square nautical miles. This can be done automatically (and without user intervention) by receipt of the AIS channel management message (AIS message 22) or manually entered via the AIS Minimal Keyboard Display (MKD) or similar input device. Once commanded or inputted the channels management information will stay in memory for 5 weeks or until a vessel exceed 500 nautical miles from the defined region. AIS channel management commands can only be automatically overridden via another channel management message for the same defined region or manually overridden or erased by the user via the unit’s channel (regional frequencies) management function—read more. Note, reinitializing or resetting your AIS or transmission channels will not necessarily reprogram your unit back to default channels.

Q:  Can I use my marine AIS in an emergency or for distress messaging? 

A:  Although not prohibited (see 33 CFR § 164.46(d)(3)), be aware that AIS safety related text messages are not currently monitored or acted upon as Global Maritime Distress Safety Systems (GMDSS) alert messages by the Coast Guard or other maritime search and rescue authorities. Therefore, AIS should not be relied upon as the primary means for broadcasting distress or urgent communications, nor used in lieu of GMDSS such as Digital Selective Calling radios which are designed to process distress messaging. Nonetheless, AIS remains an effective means to augment GMDSS and provides the added benefit of being seen (on radar or chart displays), in addition to being heard (via AIS text messaging) by other AIS users within VHF radio range. For further guidance, see USCG Safety Alert 5-10. Also, see the International Maritime Organization’s (COMSAR) Circular 46, USE OF AIS SAFETY-RELATED MESSAGING IN DISTRESS SITUATIONS.

Q:  What is UTC?

A:  Coordinated Universal Time (UTC) is a high-precision atomic time standard. UTC has uniform seconds defined by International Atomic Time (TAI), with leap seconds announced at irregular intervals to compensate for the earth's slowing rotation and other discrepancies. Leap seconds allow UTC to closely track Universal Time (UT), a time standard based not on the uniform passage of seconds, but on Earth's angular rotation.

Q:  What is the range marine AIS covers?

A:  Normally, vessels with an AIS receiver connected to an external antenna placed on 15 meters above sea level, will receive AIS information within a range of 15-20 nautical miles. Shore side base stations on higher ground may extend the range up to 40-60 nm, even behind remote mountains, depending on elevation, antenna type, obstacles around antenna and weather conditions. The most important factor for better reception is the elevation of the antenna. The higher, the better.

Q:  Will marine AIS replace radar?

A:  AIS is a useful source of additional information available to the OOW. Information received via AIS supplements and improves radar information and that derived from other navigational systems. AIS is therefore a valuable aid to assist in collision avoidance.

There always will be ships without AIS onboard. However, radar detects targets independent of the target’s onboard equipment. Therefore, AIS cannot replace radar, which is, in many ways, a ‘complete’ system.

Q:  How does marine AIS supplement radar information?

A:  In addition to radar, AIS has the following benefits:

  • Automatic vessel identification;
  • Automatic provision of heading, course over ground (COG) and speed over ground (SOG), as derived from external sensors;
  • Automatic provision of CPA (Closest Point of Approach) and Time to Closest Point of Approach (TCPA);
  • Improved vessel tracking (no target swap);
  • Generally greater range, although in some circumstances e.g. mountainous areas, this may only be achieved with the provision of shore-based repeater stations;
  • AIS can also be used as an aid to navigation and possibly replace racons;
  • Greater positional accuracy, dependent on the position input sensor;
  • Provides information in radar shadow areas (‘sees’ around bends and behind islands);
  • Near real time maneuvering data;
  • No loss of targets in sea, rain and snow clutter;
  • In addition to radar, AIS has the following benefits:
  • Automatic vessel identification;
  • Automatic provision of heading, course over ground (COG) and speed over ground (SOG), as derived from external sensors;
  • Automatic provision of CPA (Closest Point of Approach) and Time to Closest Point of Approach (TCPA);
  • Improved vessel tracking (no target swap);
  • Generally greater range, although in some circumstances e.g. mountainous areas, this may only be achieved with the provision of shore-based repeater stations;
  • AIS can also be used as an aid to navigation and possibly replace racons; greater positional accuracy, dependent on the position input sensor;
  • Provides information in radar shadow areas (‘sees’ around bends and behind islands);
  • Near real time maneuvering data;
  • No loss of targets in sea, rain and snow clutter;

Q:  What are the main limitations of marine AIS?

A:  AIS like any system does have some limitations.  

Data received is only as good as the data entered into the AIS. To ensure that correct AIS information is broadcast to other vessels and shore authorities, mariners are reminded to enter current voyage related data such as draught, type of hazardous cargo, destination and ETA properly at the beginning of each voyage and whenever changes occur.

Not all ships carry AIS. The OOW should always be aware that other ships, in particular pleasure craft and fishing vessels, may not be fitted with AIS. Also not all vessels accurately report all AIS information.

The AIS unit may not, in all cases, be installed in accordance with the IMO Guidelines. This can result in poor performance and erroneous transmissions.

The officer on watch should always be aware that AIS fitted on other ships as a mandatory carriage requirement, may, under certain circumstances, be switched off, particularly where international agreements, rules or standards provide for the protection of navigational information.

AIS is subject to the vagaries and limitations of VHF-FM propagation.

Mariners should be aware the accuracy of AIS positional information is the accuracy of the EPFD connected. For example, LORAN C can be used, but will typically have a far lower accuracy than GNSS.

Mariners are reminded to periodically check that correct information is being broadcast by their own vessel, particularly position, heading (provided by the ships master gyro) and speed.

The mariner must always remember that AIS is just one of the several tools available to watch-keepers, to fulfill their obligations under the Collision Regulations.

Q:  How does the master know that the information received from another AIS unit is accurate?

A:  The master should authenticate the information received by his AIS unit bycross-checking with his radar and/or by other means.

Q:  Why do marine AIS messages not include the rudder angle?

A:  Rudder angle information is not a required AIS sensor input and may not always be representative of the actual movement of the vessel. Transmitting rudder angle information may mislead the recipient and can therefore be dangerous. On the other hand, Rate of Turn (ROT) information is included in AIS, as this is a SOLAS carriage requirement on board vessels of over 50,000 gross tonnage.

Q:  How is marine AIS information displayed?

A:  The display panel with the unit is often the only means of showing AIS received data. Together with a keypad, this basic configuration is known as a Minimum Keyboard and Display (MKD). The display part of a MKD, as a minimum, consists of three lines of data, each showing bearing, range and name of the target. In practice, most MKDs display more lines of data and may also have a simple graphical display, showing the relative location of targets, rather like the Plan Position Indicator of a radar. To achieve the full benefits of AIS, information ought to be display graphically on a radar, ECDIS or on its own dedicated display. Recognizing this, IMO has mandated that from 1 July 2008 onwards, all new radar installations must be able to display AIS targets. The ability to display AIS information on radar or ECDIS depends entirely if the radar/ECDIS has been designed or modified for this purpose. If so, the connection can easily be made by a qualified installer.Equipment manufacturers are the best source of information and available options in this regard.

Q:  What is the accuracy of navigational information provided?

A:  The accuracy of navigational information such as position, course, speed etc. output by AIS, depends on the accuracy and proper operation of the sensors used. There is an indication of the positional accuracy transmitted by AIS (‘low’ or ‘high’), depending on whether GNSS or DGNSS is used. Further, the accuracy of data, such as voyage related data, depends on the accuracy with which this is entered and the frequency of its update. Masters must always bear in mind that a third party manually enters some the information they receive.

Q:  How will marine AIS contribute to the prevention of collisions?

A:  AIS should not be used as an anti- collision device in isolation. It should be used in conjunction with all means available to assist the mariner in assessing the risk of collision. It is important to note that there will always be other vessels that do not have AIS. IMO recognises the potential of AIS as an anti-collision device and may recommend AIS as such a device in due course. In summary, AIS is a valuable navigational aid, one of several on the bridge of a ship. It can assist in the early appraisal and subsequent resolution of a close quarters situation, or of a risk of collision. Initially, detection by AIS alone should be considered in thesame way as detection by radar alone, with particular caution being exercised until the AIS information has been verified by other means.

Q:  Is there a limit on the length of marine AIS messages?

A:  Yes. All AIS messages have a predefined structure and length, as specified in ITU-R Recommendation M.1371-1. Each AIS message occupies at least one slot of the VHF data link. This can extend to a maximum of 5 slots (as in the of short safety related text messages; which translates to approximately 158 characters of text).

Q:  Should marine AIS data be integrated on the same display as information from other sensors in a VTS?

A:  Ideally, yes. All sensor information should be integrated on a single display. This will enhance situational awareness. The operator should have the ability to customize the display to suit the task at hand.

Q:  Are marine AIS messages limited to safety information?

A:  Yes. ITU-R Recommendation M.1371-1 limits transmission on AIS designated channels to maritime safety related messages. In addition, IMO has permitted the exchange of seven other ancillary messages, for a test period of four years. Examples of such messages are number of persons on board, meteorological and hydrological information, indication of dangerous cargo, status of fairway etc.

Q:  Under what circumstances can the marine AIS unit be switched off?

A:  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 the ship or where security incidents are imminent, the AIS may be switched off. In port, AIS should be operated in accordance with port requirements. Oil terminals in particular, may have special requirements. Actions of this nature should always be recorded in the ship’s logbook, together with the reason for doing so. The master should restart the AIS as soon as the source of danger has disappeared. Ship’s own data will be transmitted after a two minute initialisation period.

Q:  Will marine AIS messaging grow to include commercial usage?

A:  No. Commercial messages should not be transmitted on the designated AIS frequencies – channels 87B and 88B (AIS 1 and AIS 2). Further, AIS is not the ideal tool for routine commercial correspondence. It is best to use other available means for this purpose.

Q:  Can I get DGNSS corrections over the AIS link?

A:  Yes, if the administration decides to do so. The message structure and technical approach have been defined in the IALA AIS Guidelines. It is important to note that such corrections will only correct theinternal GNSS. Any external GNSS equipment interfaced to the AIS will not be corrected by such messages.

Q:  How is meteorological/hydrological information displayed?

A:  A message structure has been adopted by IMO that allows the transmission of meteorological and hydrological information. At this time, broadcast and display of this information is a matter for manufacturers and authorities.

Q:  Why am I unable to see an AIS vessels' name or other static information (dimensions, call sign, etc.)?

A:  Shipboard AIS units autonomously broadcast two different AIS messages: a 'position report' which includes the vessels dynamic data (e.g. latitude, longitude, position accuracy, time, course, speed, navigation status); and, a 'static and voyage related report' which includes data particular to the vessel (e.g. name, dimensions, type) and regarding its voyage (e.g. static draft, destination, and ETA). Position reports are broadcasted very frequently (between 2-10 seconds-depending on the vessels speed-or every 3 minutes if at anchor), while static and voyage related reports are sent every six minutes; thus it is common and likely that an AIS user will receive numerous position reports from a vessel prior to receipt of the vessels' name and type, etc.

Q:  Why do I sometimes see more than one vessel with the same MMSI or vessel name (i.e. NAUT)?

A:  AIS users are required to operate their unit with a valid MMSI, unfortunately, some users neglect to do so (for example, use: 111111111, 123456789, 00000001, their U.S. documentation number, etc). A valid MMSI will start with a digit from 2 to 7. AIS users whom encounter a vessel using MMSI: 1193046 or named: NAUT should notify the user that their AIS unit is broadcasting improper data; see Nauticast AIS-MMSI Technical Bulletin for further information. All AIS users should check the accuracy of their AIS data prior to each voyage, and, particularly units that have been shutdown for any period of time.

Q:  What kind of information is broadcast for each ship and how often is it updated?

A:  A Class A marine AIS transponder broadcasts the following information every 2 to 10 seconds while underway, and every 3 minutes while at anchor:

  • MMSI number - unique referenceable identification
  • Navigation status - “at anchor”, “under way using engine” or “not under command”
  • Rate of turn - right or left, 0 to 720 degrees per minute
  • Speed over ground - 1/10 knot resolution from 0 to 102 knots.
  • Position accuracy - differential GPS or other and an indication if RAIM processing is being used
  • Longitude - to 1/10000 minute and Latitude - to 1/10000 minute
  • Course over ground - relative to true north to 1/10th degree
  • True Heading - 0 to 359 degrees derived from gyro input
  • Time stamp - The universal time to nearest second that this information was generated
  • In addition, the Class A AIS unit broadcasts the following information every 6 minutes:
  • MMSI number - same unique identification used above, links the data above to described vessel
  • IMO number - unique referenceable identification (related to ship’s construction)
  • Radio call sign - international call sign assigned to vessel, often used on voice radio
  • Name - name of ship, 20 characters are provided
  • Type of ship/cargo - there is a table of possibilities that are available
  • Dimensions of ship - to nearest meter
  • Location on ship where reference point for position reports is located
  • Type of position fixing device - various options from differential GPS to undefined
  • Draught of ship - 1/10 meter to 25.5 meters (note “air-draught” is not provided)
  • Destination - 20 characters are provided
  • Estimated time of Arrival at destination - month, day, hour, and minute in UTC

Q:  Which VHF channels or frequencies are used with AIS?

A:  AIS transponders and receivers use two VHF radio frequencies: 161.975 MHz (AIS1, or channel 87B) and 162.025 MHz (AIS2, or channel 88B). 

Q:  Can I use my marine AIS in an emergency or for distress messaging?

A:  Yes, but, be aware that AIS safety related text messages are not -currently- received, processed, recognized or acted upon as Global Maritime Distress Safety Systems (GMDSS) messages would be by some coast guards or other maritime first responders. Therefore, AIS should not be relied upon as the primary means for broadcasting distress or urgent communications, nor used in lieu of GMDSS such as Digital Selective Calling radios which are designed to process distress messaging. Nonetheless, AIS remains an effective means to augment GMDSS and provides the added benefit of being 'seen' (on radar or chart displays), in addition to being 'heard' (via text messaging) by other AIS users within VHF radio range.

Q:  What is the difference between Class A and Class B marine AIS equipment?

A:  Class A devices are designed to meet the current IMO Performance Standards. SOLAS Chapter V (Safety of Navigation) dictates their carriage requirement. Carriage of Class A units may be required for other vessels as domestic or regional carriage requirements dictate.

Q:  Class B units, which vessels can they be used on?

A:  Class B devices may not necessarily meet all the performance requirements specified by IMO MSC Resolution 74 (69) Annex 3. They are designed to operate harmoniously with Class A units on the VHF data link. The Class B units may be used on craft not subject to SOLAS.

Q:  How much does a marine AIS cost?

A:  A type-approved AIS can range in price between $500 (AIS Class B) and $4,000 (AIS Class A), not including installation cost which will vary considerably depending on the level of integration of the AIS with other shipboard systems (e.g. radar, speed log, rate of turn indicator, navigation positioning system, ECDIS, etc.).

Q:  Single channel switching receiver and full time dual channel receivers. What are the differences between these models?

A:  All the units can receive AIS information from either AIS channel. The single channel switching receiver can only receive information on one channel at a time but automatically switches between both channels.

The dual channel receiver can receive all AIS broadcast information from both AIS channels simultaneously and consolidate the information from both channels into a single data stream. This generally means you will acquire new vessels sooner with the dual channel units and you will also get the full information about a vessel in a shorter period of time.

Q:  I don’t have a spare serial port on my computer. How do I connect an AIS receiver to my computer?

A:  You typically have two options.  The first option is to use a serial to USB adaptor. Connect the serial end to the AIS receiver and the USB end to a spare USB port on your computer. Make sure you know which COM port has been assigned to the USB serial port and configure your software appropriately.

Q:  Who should have marine AIS fitted

A:  The international requirement for the carriage AIS as ship-borne navigational equipment on vessels is detailed within Chapter V (Safety of Navigation) Regulation 19, of the SOLAS Convention. This requires that:

“All ships of 300 gross tonnage and upwards engaged on international voyages and cargo ships of 500 gross tonnage and upwards not engaged on international voyages and passenger ships irrespective of size shall be fitted with Automatic Identification System (AIS), as follows:

  • Ships constructed on or after 1 July 2002;
  • Ships engaged on international voyages constructed before 1 July 2002;
  • In the case of passenger ships not later than 1 July 2003;
  • In the case of tankers, not later than the first survey for safety equipment* after 1 July 2003;
  • In the case of ships, other than passenger ships and tankers, of 50,000 gross tonnage and upward, not later than 1 July 2004;
  • In the case of ships, other than passenger ships and tankers, of 300 gross tonnage and upwards but less than 50,000 gross tonnage, not later than the first survey for safety equipment after 1 July 2004 or by 31 December 2004, whichever occurs earlier; * and
  • Ships not engaged on international voyages constructed before 1 July 2002, not later than 1 July 2008.

As determined at the IMO Conference of Contracting Governments to the International Convention for the Safety of Life at Sea, 1974: 9-13 December 2002.

Ships to which Regulation 19 of Chapter V of SOLAS do not apply are broadly fishing vessels, pleasure craft, support vessels and inland waterway vessels. It is expected that national administrations and the operators of these vessels will quickly realise the potential of AIS and its capability to enhance the safety of navigation.


AIS Regulations / Mandate Questions

Q: What is the marine AIS rule and are there alternatives to the rule for small businesses?

A: The U.S. Coast Guard has developed rules applicable to both U.S. and foreign-flag vessels that require owners and operators of most commercial vessels operating on U.S. navigable waters to be outfitted with an Automatic Identification System (AIS). These rules are part of our domestic and international effort to increase the security and safety of maritime transportation. Initial AIS rules became effective on July 1st, 2003 (68 FR 60559) and were subsequently amended on January 30th, 2015 (80 FR 5281), so as to require that all vessels denoted 33 CFR § 164.46(d)be outfitted with an USCG type-approved and properly installed operational AIS no later than March 1st, 2016.type-approved and properly installed, operational AIS no later than March 1st, 2016. There are no alternatives to this rule, however, many small business may meet the carriage requirement by purchasing a lower cost AIS Class B device in lieu of a Class A. See our Small Entity Compliance Guide to AIS and our AIS FAQ#4 below for further information.

Q: Do marine AIS Class B devices meet current USCG AIS carriage requirements?

A: Yes, a small segment of mandatory AIS users (see 33 CFR § 164.46(b)(2)) can use a Coast Guard type-approved AIS Class B device in lieu of a Class A device—AIS Class A vs B comparison. Note, U.S. AIS carriage requirements can only be met by USCG type-approved equipment which displays a USCG 165.155/156 Approval Number.  A listing of all USCG type-approved equipment can be found at the Coast Guard Maritime Information Exchange (CGMIX) [EQList Search, Select: Approval Series Name--Shipborne AIS]. Voluntary AIS users may avail themselves of either a AIS Class A or B device, but, such device must be FCC certified for its use in the United States. For a listing of FCC certified AIS equipment use the FCC OET Equipment Authorization Search Form [Select: Equipment Class--AIS).

Q: Will it be necessary to have electronic navigational charts for use with the AIS?

A: Eventually. Section 410 of the Coast Guard and Marine Transportation Act of 2004 (P.L.108-293) directs the Coast Guard to prescribe regulations that will require most commercial vessels "while operating on the navigable waters of the United States...be equipped with and operate an electronic chart system (ECS)"; and, that this system be integrated with AIS. A rulemaking implementing this additional requirement is in development. Till these regulations are finalized, AIS is not required to be displayed on an ECS or other external display system; although it is highly recommended. The full benefits of AIS are only achieved when it is fully integrated and displayed on other shipboard navigation systems (e.g. Electronic Charts Data & Information System (ECDIS), ECS, Radar, Automatic Radar Plotting Aide (ARPA), Tracking Devices, personal software, etc.).

Q:  Are fishing vessels subject to AIS carriage, and, are onboard Vessel Monitoring Systems (VMS) an acceptable substitute for AIS? 

A:  Yes and no. Commercial self-propelled fishing vessels of 65 feet or more in length are subject to AIS carriage requirements; see 33 CFR 164.46(b). Per 33 CFR § 164.46(b)(2), fishing industry vessels (i.e. fishing processors, tenders, and vessels as defined in 46 U.S.C. 2101) may use lower-cost AIS Class B units in lieu of Class A devices. However, a NOAA Vessel Monitoring Systems (VMS) are not an acceptable substitute for AIS because they are not inter-operable or compatible. Each uses different communication systems, protocols, reporting rates, and, most importantly VMS does not, nor is it designed to, mitigate collisions or enhance users’ situational awareness. Read more...

Q:  Is the Coast Guard broadcasting AIS Aids to Navigation Reports? 

A:  Yes. The U.S. Coast Guard and other authorized agencies and organizations (i.e., U.S. Army Corps of Engineers, National Oceanic and Atmospheric Administration, Marine Exchange of Alaska) are transmitting AIS ATON Reports and marine safety information via AIS (see our Special Notice 01-2014). The exact content, location, and times of these transmissions will be announced in the Coast Guard Local Notices to Mariners (LNM) and denoted in Coast Guard Light List.

Note, AIS AtoN can autonomously and at fixed intervals broadcast the name, position, dimensions, type, characteristics and status from or concerning an aid to navigation.  AIS AtoN can be either physical (physically fitted to the AtoN), synthetic (physically fitted somewhere other than to the AtoN) or virtual (physically nonexistent, but capable of being portrayed on AIS-capable displays). AIS AtoN can also be used to broadcast both laterally (e.g., Port Hand Mark) and non-laterally significant marine safety information (e.g.,environmental data, tidal information, and navigation warnings). For further information on AIS ATON refer to the various IALAGuidelines and Recommendations.

Q:  Are naval ships required to fit marine AIS?

A:  No. Chapter V of the SOLAS Convention does not apply to them. However, national administrations may require the installation of AIS on board naval vessels. National administrations may dictate the use of AIS on board naval vessels. Many navies have outfitted their vessels with AIS. However, they may not always be transmitting AIS information (e.g. operating in a ‘receive only’ mode).


Install / Programming Questions

Q:  How do I install and program my marine AIS; and, what is a MMSI?

A:  AIS devices should be installed taking into consideration the guidelines developed by the International Maritime Organization (IMO Safety of Navigation Circular.227, GUIDELINES FOR THE INSTALLATION OF A SHIPBORNE AUTOMATIC IDENTIFICATION SYSTEM) or the National Marine Electronics Association (NMEA 0400-4.00, INSTALLATION STANDARD. Programming an AIS varies by class. AIS Class B are not user configurable; therefore, owners should contact their AIS manufacturer or retailer for instructions. AIS Class A owners, may encode their own device, but will require knowing the unit password to do so. Either class should be encoded to reflect the vessel’s official data as provided in its radio station license or state registration (for those vessels licensed by rule), and, as provided in the USCG AIS Encoding Guide. A unique and official 9-digit Maritime Mobile Service Identity (MMSI) number is required for every AIS station. To obtain one see our MMSI page. Note, AIS users must ensure their AIS is always in effective operating condition and broadcasting accurately (33 CFR §164.46(d)). Failure to do so could subject a person to civil penalties not to exceed $25,000 (46 U.S.C. 70119). Note, each USCG type-approved AIS has an internal built-in integrity tester that mitigates the need to send TEST text messages. For further guidance on the programming and use of AIS text messages please read USCG Safety Alert 05-10.

Q:  Does the installation of the marine AIS require additional equipment in order for the AIS to operate properly? 

A:  No, however, Chapter V,Regulation 19 of the Safety of Life at Sea Convention (SOLAS), as stated in 33 CFR § 164.46(d)(2), does require certain vessels on international voyage to interface it to other existing onboard equipment (i.e. transmitting heading device, gyro, rate of turn indicator); domestic vessels, are not currently required to do so, however it is highly recommended.

Q:  Do marine AIS Class B devices meet current USCG AIS carriage requirements? 

A:  Maybe. Per 33 CFR 164.46(b)(2), use of an AIS Class B device, in lieu of a mandatory Class A device, is permissible, but, only on: dredges; fishing industry vessels; and, vessels certificated to carry less than 150 passengers, that do not operate in a Vessel Movement Reporting System (VMRS) area defined in Table 161.12(c) or at speeds in excess of 14 knots. See a comparison of Class A and Class B/CS AIS.

Q:  Is the USCG considering expanding AIS carriage to other vessels or outside of VTS areas? 

A:  Yes. On January 30th, 2015 the Coast Guard published a Final Rule (80 FR 5281, corrected 80 FR 17326), which on March 2nd, 2015, expands AIS carriage (68 FR 60599) to most commercial vessels operating on any U.S. navigable waters (see our Fact Sheet for those affected), and harmonizes U.S. AIS requirements with Regulation V/19.2.4 of the Safety of Life at Sea Convention and § 102 of the Maritime Transportation Security Act of 2002. The docket containing comments submitted, supporting documents, and the regulatory analysis to this and our proposed rulemaking (73 FR 76295) can be found at www.regulations.gov [Search: USCG-2005-21869]. See printer-friendly PDF formats of these 2015 requirements, our 2008 proposed rule, an amalgamation of both, our 2003 requirements, and, a chart-comparison of all three.

Q:  What type of VHF antenna do I need for an AIS receiver?

A:  The VHF antenna should fulfill at least the following requirements:

  • Antenna type: Vertical radiator
  • Antenna gain: 0 – 3 dBd
  • Impedance: 50 ohm

Q:  Will an AIS receiver work with manufacturers proprietry data systems?

A:  All networks that can handle NMEA VDM serial data at the speed 38400 baud will be able to handle AIS data.

Q:  Can I connect my GNSS to the AIS?

A:  Practically all AIS units have an in-built GNSS receiver (such as GPS or GLONASS). This is required primarily to provide accurate UTC. The GNSS antenna and receiver are part of the ship’s AIS equipment, separate from any other GNSS equipment onboard. AIS can use positional and other data from the ship’s GNSS or other radio-navigation system that is being used to navigate the ship. However, if positional information is lost from the ship’s GNSS or other equipment, the AIS will transmit position and other data from the internal GNSS. Regardless, any GNSS connected to the AIS should comply with IMO Resolution MSC.112 (73) (Revised performance standards forship-borne Global Positioning System (GPS) receiver equipment) and IEC Test Standard 61108-1.

Vitally, GPS units that comply with the older IMO performance standard should not be interfaced to the AIS. This is because differences between the two standards are considerable. Under the new standard, there is a requirement for integrity monitoring (RAIM), satisfactory operation in typical interference conditions, higher accuracies for position, Course Over Ground (COG) and Speed Over Ground (SOG) output, higher update display rate (every second, as opposed to every two seconds). The most significant of these are the RAIM requirement and interference rejection standards.

Q:  Can I connect my gyro compass to the AIS?

A:  AIS requires the input of the ships gyro or transmitting heading device (THD), which meets the relevant IMO and IEC standards. Without heading information, the presentation of the ship shape will not be generated. However, in this case, the isosceles triangle representing the ships position will be aligned with the COG (without the heading marker) on the display of receiving stations.


Q:  What are the basic steps to install an AIS receiver?

A:  All AIS receivers essentially have the same four connections. One connection is for a standard marine VHF antenna. This is usually via a BNC connector. The second connection is NMEA position data input from either GPS/Chartplotter or your PC. The Third is AIS Data output which is connected to your chartpotter/PC. The forth connection is for 12 volt DC power.

Once these connections have been made, simply configure your chartplotter or PC software to utilize the output data stream. Note that AIS receivers use 38400 baud by default so make sure you configure your PC serial port and program appropriately.

Q:  Can I use an existing marine VHF antenna?

A:  Yes, you can use an existing VHF antenna on its own or you can use an antenna splitter to share one VHF antenna between your VHF/DSC radio and your AIS receiver. While transmitting on the VHF radio, you may see some interruption of incoming AIS signals. Since AIS broadcasts from each ship are repeated every few seconds, this is not normally noticeable. Alternatively, use a dedicated AIS antenna.

Q:  How does the master know that his AIS unit is working properly?

A:  AIS provides:

  • A built-in integrity test (BIIT) running continuously or at appropriate intervals;
  • Monitoring of the availability of the data;
  • An error detection mechanism of the transmitted data; and,
  • Error checking of the received data.

If no sensor is installed or if the sensor (e.g. the gyro) fails to provide data, the AIS automatically transmits the "not available" data value. However, the integrity check cannot validate the accuracy of the data received by the AIS. The AIS requires that an alarm output (relay) be connected to an audible alarm device or the ship’s alarm system, if available. Alternatively, the BIIT alarm system may use the alarm messages’ output on the Presentation Interface (PI), provided its alarm system is AIS compatible.

Q:  Is there any calibration of the marine AIS equipment needed?

A:  No – a correctly installed AIS unit should not need any further calibration to continue operating. The Built-In Integrity Test component of each AIS will activate an alarm should the unit fail to operate in accordance with specified parameters.

Q:  Is there any set up (initial/regular/frequent) of the AIS equipment needed?

A:  Yes. Static data (vessel name, call sign, MMSI, IMO number etc) must be entered upon installation in accordance with the ship’s registration documents. Voyage-related data (draught, destination, ETA, navigation status etc) must be entered at the commencement of each voyage or if there are any changes. It is recommended that both static and voyage-related data be checked and updated at appropriate intervals, as required. The failure to correct the vessel’s navigational status when it changes (a vessel comes alongside from being underway, for example) is commonly overlooked.

Q:  Is there any training on the use of marine AIS available?

A:  All AIS manufacturers provide operating manuals may well offer initial training on their equipment. It is recommended that ship owners and managers take advantage of these sources and incorporate AIS training in their ISM procedures. All About AIS offer web based training on AIS, visit our events section for more information.

Q:  Does the installation of the AIS require additional equipment in order for the AIS to operate properly?

A:  Maybe. Most AIS do not need additional equipment (sensors) in order to operate; a few however, do require interfacing with an external global navigation positioning device (e.g. dGPS, GPS, GLONASS) in order to accurately calculate and broadcast position, course, and speed--thus requiring this equipment to properly operate. Although not required for the operation of AIS, Chapter V, Regulation 19 of the Safety of Life at Sea Convention (SOLAS), as stated in 33 CFR § 164.46(a)(2), does require certain vessels--those on international voyage--to also interface other onboard equipment (i.e. transmitting heading device, gyro, rate of turn indicator) to the AIS; domestic vessels, not on international voyage, are not currently required to do so, however are highly recommended to.

Q:  What is a MMSI and where can I get one for my AIS?

A:  A unique and official Maritime Mobile Service Identity (MMSI) number is required for every AIS unit.

Q:  I have hooked up my marine AIS receiver. Why don’t I see ships immediately?

A:  It normally takes a few seconds for ships to appear since the receiver needs to pick up a transmission from the remote ships’ transponders. The system allows for ships to rebroadcast their information every few seconds so within a minute you will typically see nearby ships appear on your navigation package.

Q:  The ships show up as numbers? I thought I would also see the name of the ship.

A:  Just wait. Ships broadcast voyage information every few seconds but also broadcast full ship information every 6 minutes. So after a few minutes, you should see complete information for every ship that the AIS receiver has picked up.