Annex 17 - Automatic Identification Systems (AIS)

AIS has been operational on all ships of over 300GT on international voyages since 31 December 2004. It is a major development in improving safety of navigation and the monitoring of passing traffic by coastal states. Mariners should therefore take careful note of the following guidance and the IMO Operational Guidelines which follow in order to ensure that they fully understand its operational limitations and correct use.

Regulation 19.2.4 lays down the timetable for fitting AIS to ships in the given categories.

EU Directive 2002/59/EC (the "Vessel Traffic Monitoring Directive") lays down carriage requirements for AIS based on the SOLAS V/19 requirements but with the dates for application to all ships which call at a port of a Member State brought forward, and a lower tonnage limit of 300 gt for such vessels (as opposed to 500 gt in SOLAS V/19.2.4)

The implementation dates laid down by SOLAS V/19 and the VTMD are summarised in the following table:




1. Ships constructed on or after 1 July 2002 (“new ships”)

Date of build (V/

2. Ships engaged on international voyages constructed before 1 July 2002 (“existing ships”)

2.1 Passenger ships

1 July 2003 (V/

2.2 Tankers

1st survey for safety equipment on or after 1 July 2003 (V/

2.3 Ships, other than passenger ships and tankers, of 50000 gt or more

1 July 2004 (V/

2.4 Ships, other than passenger ships and tankers, of 300 gt and upwards but less than 50000 gt.

1st survey for safety equipment on or after 1 July 2004 or by 31 December 2004, whichever occurs earlier. (V/

2.5 Ships,other than tankers or passenger ships, 10000 - 49999 gt which call at port of an EU Member State.

1 July 2005 (EU Directive 2002/59/EC)

2.6 Ships, other than tankers or passenger ships, 3000 -9999 gt which call at port of an EU Member State.

1 July 2006 (EU Directive 2002/59/EC)

2.7 Ships, other than tankers or passenger ships, 300 - 2999 gt which call at port of an EU Member State.

1 July 2007 (EU Directive 2002/59/EC)

NOTE: This table incorporates changes to the AIS carriage requirements adopted by a Diplomatic Conference of Contracting IMO Governments on Marine Security in December 2002



AIS has the potential to reduce the work of the watchkeeper by automatically providing coastal stations with the information which they require under mandatory or voluntary reporting schemes as well as for VTS purposes. To this end it is essential that the Static and Voyage-related information is at all times correctly programmed and that the Dynamic inputs are functioning correctly. (See IMO Guidelines, para 12). Additionally the mariner must consider the following:

a.) The coastal station may not be equipped to monitor AIS.

b.) The ship may be within a reporting system but out of VHF range of the coastal station.

c.) Reporting requirements may require more information than the AIS transmits.


AIS provides identification of targets together with the static and dynamic information listed in the IMO Guidelines para.12. Mariners should, however, use this information with caution noting the following important points:

a.) Collision avoidance must be carried out in strict compliance with the COLREGs. There is no provision in the COLREGs for use of AIS information therefore decisions should be taken based primarily on visual and/or radar information.

b.) The use of VHF to discuss action to take between approaching ships is fraught with danger and still discouraged. (See MGN 324 (M+F) - Radio: Operational Guidance on the Use Of VHF Radio and Automatic Identification Systems (AIS) at Sea) The MCA’s view is that identification of a target by AIS does not remove the danger. Decisions on collision avoidance should be made strictly according to the COLREGs

c.) Not all ships will be fitted with AIS, particularly small craft and fishing boats. Other floating objects which may give a radar echo will not be detected by AIS.

d.) AIS positions are derived from the target’s GNSS position. (GNSS = Global Navigation Satellite System, usually GPS). This may not coincide with the radar target.

e.) Faulty data input to AIS could lead to incorrect or misleading information being displayed on other vessels. Mariners should remember that information derived from radar plots relies solely upon the data measured by the own-ship’s radar and provides an accurate measurement of the target’s relative course and speed, which is the most important factor in deciding upon action to avoid collision. Existing ships of less than 500 gt. Which are not required to fit a gyro compass are unlikely to transmit heading information.

f.) A future development of AIS is the ability to provide “pseudo” navigation marks by enabling coastal authorities to provide an AIS symbol on the display in any position. Mariners should bear in mind that this ability could lead to the appearance of “spurious” AIS targets and therefore take particular care when an AIS target is not complemented by a radar target. It should be noted though that AIS will sometimes be able to detect targets which are in a radar shadow area.


4.) IMO RESOLUTION A.917 (22) AUTOMATIC IDENTIFICATION SYSTEMS           (AIS) [As amended by Resolution A.956(23)]



RECALLING Article 15(j) of the Convention on the International Maritime Organization concerning the functions of the Assembly in relation to regulations and guidelines concerning maritime safety,

RECALLING ALSO the provisions of regulation V/19 of the International Convention for the Safety of Life at Sea (SOLAS), 1974, as amended, requiring 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 to be fitted with an automatic identification system (AIS), as specified in SOLAS regulation V/19, paragraph 2.4, taking into account the recommendations adopted by the Organization,

HAVING CONSIDERED the recommendations made by the Maritime Safety Committee at its seventy-third session and the Sub-Committee on Safety of Navigation at its forty-seventh session,

1.) ADOPTS the Guidelines for the onboard operational use of Shipborne Automatic Identification Systems (AIS) set out in Annex to the present resolution;

2.) INVITES Governments concerned to take into account these Guidelines when implementing SOLAS regulations V/11, 12 and 19;

3.) ALSO INVITES Governments, which set regional frequencies requiring manual switching which, from the safety viewpoint, should be limited to temporary situations, to notify the Organization of such areas and designated frequencies, for circulation of that information until 1 April 2002;

4.) REQUESTS the Maritime Safety Committee to keep the Guidelines under review and amend them as appropriate.




1.) These Guidelines have been developed to promote the safe and effective use of shipborne Automatic Identification Systems (AIS), in particular to inform the mariner about the operational use, limits and potential uses of AIS. Consequently, AIS should be operated taking into account these Guidelines.

2.) Before using shipborne AIS, the user should fully understand the principle of the current Guidelines and become familiar with the operation of the equipment, including the correct interpretation of the displayed data. A description of the AIS system, particularly with respect to shipborne AIS (including its components and connections), is contained in Annex 1.


Not all ships carry AIS.

The officer of the watch (OOW) should always be aware that other ships and, in particular, leisure craft, fishing boats and warships, and some coastal shore stations including Vessel Traffic Service (VTS) centres, might not be fitted with AIS.

The OOW should always be aware that AIS fitted on other ships as a mandatory carriage requirement, might, under certain circumstances, be switched off on the master's professional judgement.

3.) The internationally-adopted shipborne carriage requirements for AIS are contained in SOLAS regulation V/19. The SOLAS Convention requires AIS to be fitted on certain ships through a phased implementation period spanning from 1st July 2002 to 1st July 2008. In addition, specific vessel types (e.g. warships, naval auxiliaries and ships owned/operated by governments) are not required to be fitted with AIS. Also, small vessels (e.g. leisure craft, fishing boats) and certain other ships are exempt from carrying AIS. Moreover, ships fitted with AIS might have the equipment switched off. Users are therefore cautioned to always bear in mind that information provided by AIS may not be giving a complete or correct ‘picture’ of shipping traffic in their vicinity. Guidance in this document on the inherent limitations of AIS and their use in collision avoidance situations (see paragraphs 39 to 43) should, therefore, be heeded.


4.) AIS is intended to enhance: safety of life at sea; the safety and efficiency of navigation; and the protection of the marine environment. SOLAS regulation V/19 requires that AIS exchange data ship-to-ship and with shore-based facilities. Therefore, the purpose of AIS is to help identify vessels; assist in target tracking; simplify information exchange (e.g. reduce verbal mandatory ship reporting); and provide additional information to assist situation awareness. In general, data received via AIS will improve the quality of the information available to the OOW, whether at a shore surveillance station or on board a ship. AIS should become a useful source of supplementary information to that derived from navigational systems (including radar) and therefore an important ‘tool’ in enhancing situation awareness of traffic confronting users.


Figure 1 AIS system overview

5.) Shipborne AIS:

  • continuously transmits ship's own data to other vessels and VTS stations;
  • continuously receives data of other vessels and VTS stations; and
  • displays this data.

6.) When used with the appropriate graphical display, shipborne AIS enables provision of fast, automatic information by calculating Closest Point of Approach (CPA) and Time to Closest Point of Approach (TCPA) from the position information transmitted by the target vessels.

7.) AIS operates primarily on two dedicated VHF channels. Where these channels are not available regionally, the AIS is capable of being automatically switched to designated alternate channels by means of a message from a shore facility. Where no shore based AIS or GMDSS sea Area A1 station is in place, the AIS should be switched manually.

8.) In practice, the capacity of the system is unlimited allowing for a great number of ships to be accommodated at the same time.

9.) The AIS is able to detect ships within VHF/FM range around bends and behind islands, if the landmasses are not too high. A typical value to be expected at sea is 20 to 30 nautical miles depending on antenna height. With the help of repeater stations, the coverage for both ship and VTS stations can be improved.

10.) Information from a shipborne AIS is transmitted continuously and automatically without any intervention or knowledge of the OOW. An AIS shore station might require updated information from a specific ship by “polling” that ship, or alternatively, might wish to “poll” all ships within a defined sea area. However, the shore station can only increase the ships’ reporting rate but not decrease it.


Ship’s data content

11.) The AIS information transmitted by a ship is of three different types:

  • fixed, or static information, which is entered into the AIS on installation and need only be changed if the ship changes its name or undergoes a major conversion from one ship type to another;
  • dynamic information, which, apart from ‘Navigational status’ information, is automatically updated from the ship sensors connected to AIS; and
  • voyage-related information, which might need to be manually entered and updated during the voyage.

12.) Details of the information referred to above are given in table 1 below:

Information item

Information generation, type and quality of information

(Maritime Mobile Service Identity)
Set on installation
Note that this might need amending if the ship changes ownership
Call sign and name Set on installation
Note that this might need amending if the ship changes ownership
IMO Number Set on installation
Length and beam Set on installation or if changed
Type of ship. Select from pre-installed list
Location of position-fixing antenna Set on installation or may be changed for bi-directional vessels or those fitted with multiple antennae


Ship’s position with accuracy indication and integrity status Automatically updated from the position sensor connected to AIS.
The accuracy indication is for better or worse than 10 m.
Position Time stamp in UTC Automatically updated from ship’s main position sensor connected to AIS.
Course over ground (COG) Automatically updated from ship’s main position sensor connected to AIS, if that sensor calculates COG.
This information might not be available.
Speed over ground (SOG) Automatically updated from the position sensor connected to AIS.
This information might not be available.
Heading Automatically updated from the ship’s heading sensor connected to AIS.
Navigational status

Navigational status information has to be manually entered by the OOW and changed, as necessary, for example:

- underway by engines
- at anchor
- not under command (NUC)
- restricted in ability to manoeuvre (RIATM)
- moored
- constrained by draught
- aground
- engaged in fishing
- underway by sail

In practice, since all these relate to the COLREGS, any change that is needed could be undertaken at the same time that the lights or shapes were changed.

Rate of turn (ROT)

Automatically updated from the ship’s ROT sensor or derived from the gyro.
This information might not be available.

Voyage related:

Ship’s draught To be manually entered at the start of the voyage using the maximum draught for the voyage and amended as required.
(e.g. – result of de-ballasting prior to port entry.)
Hazardous cargo (type)

To be manually entered at the start of the voyage confirming whether or not hazardous cargo is being carried, namely:

DG (Dangerous goods)
HS (Harmful substances)
MP (Marine pollutants)

Indications of quantities are not required.

Destination and ETA To be manually entered at the start of the voyage and kept up to date
as necessary.
Route plan (waypoints) To be manually entered at the start of the voyage, at the discretion of
the master and updated when required.

Short safety-related messages:

Free format short text messages would be manually entered, addressed either to a specific addressee or broadcast to all ships and shore stations.

Table 1 Data sent by ship

13.) The data is autonomously sent at different update rates:

  • dynamic information dependent on speed and course alteration (see Table 2),
  • static and voyage-related data every 6 minutes or on request (AIS responds automatically without user action).

Type of ship

General Reporting interval

Ship at anchor 3 min
Ship 0-14 knots 12 sec
Ship 0-14 knots and changing course 4 sec
Ship 14-23 knots 6 sec
Ship 14-23 knots and changing course 2 sec
Ship >23 knots 3 sec
Ship >23 knots and changing course 2 sec

Table 2: Report Rate of Dynamic Information

Short safety-related messages

14.) Short safety-related messages are fixed or free format text messages addressed either to a specified destination (MMSI) or all ships in the area. Their content should be relevant to the safety of navigation, e.g. an iceberg sighted or a buoy not on station. Messages should be kept as short as possible. The system allows up to 158 characters per message but the shorter the message the easier it will find free space for transmission. At present, these messages are not further regulated, to keep all possibilities open.

15.) Operator acknowledgement may be requested by a text message.

16.) Short safety-related messages are only an additional means to broadcast maritime safety information. Whilst their importance should not be underestimated, the usage of such short safety-related messages does not remove any of the requirements of the Global Maritime Distress and Safety System (GMDSS).

17.) The operator should ensure that he displays and considers incoming safety-related messages and should send safety-related messages as required.

18.) According to SOLAS regulation V/31 (Danger messages)
“The master of every ship which meets with dangerous ice, a dangerous derelict, or any other direct danger to navigation, or bound to communicate the information by all the means at his disposal to ships in the vicinity, and also to the competent authorities...”

19.) Normally this is done via VHF voice communication but “by all the means” now implies the additional use of the AIS short messages application, which has the advantage to reduce difficulties in understanding, especially when noting down the correct position.


20.) When entering any data manually, consideration should be given to the confidentiality of this information, especially when international agreements, rules or standards provide for the protection of navigational information.




21.) 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. This might be the case in sea areas where pirates and armed robbers are known to operate. Unless it would further compromise the safety or security, if the ship is operating in a mandatory ship reporting system, the master should report this action and the reason for doing so to the competent authority.The master should however restart the AIS as soon as the source of danger has disappeared. If the AIS is shut-down, static data and voyage related information remains stored. Restart is done by switching on the power to the AIS unit. Ship’s own data will be transmitted after a two minute initialization period. In ports AIS operation should be in accordance with port requirements.Manual input of data

22.) The OOW should manually input the following data at start of the voyage and whenever changes occur using the input device such as a keyboard:

  • Ship’s draught
  • hazardous cargo;
  • destination and ETA;
  • route plan (way-points);
  • the correct navigational status; and
  • safety related short messages

Check of information

23.) To ensure that own ship’s static information is correct and up-to-date, the OOW should check the data whenever there is a reason for it. As a minimum, this should be done once per voyage or once per month, whichever is shorter. The data may be changed only on the authority of the master.

24.) The OOW should also periodically check the following dynamic information:

  • positions given according to WGS 84;
  • speed over ground; and
  • sensor information.

25.) After activation, an automatic built-in integrity test (BIIT) is performed. In the case of any AIS malfunction an alarm is provided and the unit should stop transmitting.

26.) The quality or accuracy of the ship sensor data input into AIS would not however be checked by the BIIT circuitry before being broadcast to other ships and shore stations. The ship should therefore carry out regular routine checks during a voyage to validate the accuracy of the information being transmitted. The frequency of those checks would need to be increased in coastal waters.


27.) The AIS provides data that can be presented on the minimum display or on any suitable display device as described in annex 1.

Minimum display

28.) The minimum mandated display provides not less than three lines of data consisting of bearing, range and name of a selected ship. Other data of the ship can be displayed by horizontal scrolling of data, but scrolling of bearing and range is not possible. Vertical scrolling will show all the other ships known to the AIS.

Graphical display

29.) Where AIS information is used with a graphical display, the following target types are recommended for display:

Sleeping target A sleeping target indicates only the presence of a vessel equipped with AIS in a certain location. No additional information is presented until activated thus avoiding information overload.

Activated target
If the user wants to know more about a vessel’s motion, he has simply to activate the target (sleeping), such that the display shows immediately:

  • a vector (speed and course over ground),
  • the heading, and
  • ROT indication (if available) to display actually initiated course changes.

Selected target If the user wants detailed information of a target (activated or sleeping), he may select it. Then, the data received as well as the calculated CPA and TCPA values will be shown in an alpha-numeric window.

The special navigation status will also be indicated in the alpha numeric data field and not together with the target directly.

Dangerous target If an AIS target (activated or not) is calculated to pass pre-set CPA and TCPA limits, it will be classified and displayed as a dangerous target and an alarm will be given.

Lost target If a signal of any AIS target at a distance of less than a preset value is not received, a lost target symbol will appear at the latest position and an alarm will be given.


30.) The user should be familiar with the symbology used in the graphical display provided.


31.) The officer of the watch (OOW) should always be aware that other ships, and in particular leisure craft, fishing boats and warships, and some coastal shore stations including Vessel Traffic Service (VTS) centres might not be fitted with AIS.

32.) The OOW should always be aware that other ships, fitted with AIS as a mandatory carriage requirement, might switch off AIS under certain circumstances by professional judgement of the master.

33.) In other words, the information given by the AIS may not be a complete picture of the situation around the ship.

34.) The users must be aware that transmission of erroneous information implies a risk to other ships as well as their own. The users remain responsible for all information entered into the system and the information added by the sensors.

35.) The accuracy of AIS information received is only as good as the accuracy of the AIS information transmitted.

36.) The OOW should be aware that poorly configured or calibrated ship sensors (position, speed and heading sensors) might lead to incorrect information being transmitted. Incorrect information about one ship displayed on the bridge of another could be dangerously confusing.

37.) 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 built-in integrity check cannot validate the contents of the data processed by the AIS.

38.) It would not be prudent for the OOW to assume that the information received from other ships is of a comparable quality and accuracy as that which might be available on own ship.


39.) The potential of AIS as an anti-collision device is recognized and AIS may be recommended as such a device in due time.

40.) Nevertheless, AIS information may be used to assist in collision avoidance decision-making. When using the AIS in the ship-to-ship mode for anti-collision purposes, the following cautionary points should be borne in mind:

40.1) AIS is an additional source for navigational information. AIS does not replace, but supports, navigational systems such as radar target-tracking and VTS; and

40.2) the use of AIS does not negate the responsibility of the OOW to comply, at all times, with the Collision Regulations.

41.) The user should not rely on AIS as the sole information system, making use of all safety-relevant information available.

42.) The use of AIS on board ship is not intended to have any special impact on the composition of the navigational watch, which should continue to be determined in accordance with the STCW Convention.

43.) Once a ship has been detected, AIS can assist in tracking it as a target. By monitoring the information broadcast by that target, its actions can also be monitored. Changes in heading and course are, for example, immediately apparent, and many of the problems common to tracking targets by radar, namely clutter, target swap as ships pass close by and target loss following a fast manoeuvre, do not affect AIS. AIS can also assist in the identification of targets, by name or call sign and by ship type and navigational status.



Pseudo AIS information

44.) VTS centres may send information about vessels which are not carrying AIS and which are tracked only by VTS radar, via the AIS to vessels equipped with AIS. Any pseudo AIS target broadcast by VTS should be clearly identified as such. Particular care should always be taken when using information which has been relayed by a third party. Accuracy of these targets may not be as accurate as actual directly-received targets and the information content may not be as complete.

Text messages

45.) VTS centres may also send short messages either to one ship, all ships or ships within a certain range or in a special area, e.g.:

  • (local) navigational warnings;
  • traffic management information; and
  • port management information.

46.) A VTS operator may request, by a text message, an acknowledgement from the ship’s operator.
Note: The VTS should continue to communicate via voice VHF. The importance of verbal communication should not be underestimated. This is important for the VTS operator to:

  • assess vessels’ communicative ability; and
  • establish a direct communication link which would be needed in critical situations.

(D)GNSS corrections

47.) (D)GNSS corrections may be sent by VTS centres via AIS.


48.) AIS is expected to play a major role in ship reporting systems. The information required by coastal authorities in such systems is typically included in the static voyage related and dynamic data automatically provided by the AIS system. The use of the AIS long range feature, where information is exchanged via communications satellite, may be implemented to satisfy the requirements of some ship reporting systems.


49.) AIS may be used in search and rescue operations, especially in combined helicopter and surface searches. AIS enables the direct presentation of the position of the vessel in distress on other displays such as radar or ECS/ECDIS, which facilitates the task of SAR craft. For ships in distress not equipped with AIS, the On Scene Commander (OSC) could create a pseudo AIS target.


50.) AIS, when fitted to selected fixed and floating aids to navigation can provide information to the mariner such as:

  • position;
  • status;
  • tidal and current data; and
  • weather and visibility conditions.


51.) AIS will play a role in an overall international maritime information system, supporting voyage planning and monitoring. This will assist administrations to monitor all the vessels in their areas of concern and track dangerous cargo.


  • IMO Recommendation on Performance Standards for a Universal Automatic Identification System (AIS), (MSC. 74(69), annex 3).
  • IMO SOLAS Convention Chapter V [2002]
  • ITU Radio Regulations, Appendix S18, Table of Transmitting Frequencies in the VHF Maritime Mobile Band
  • ITU Recommendation on the Technical Characteristics for a Universal Shipborne Automatic Identification System (AIS) Using Time Division Multiple Access in the Maritime Mobile Band (ITU-R M.1371)
  • IEC Standard 61993 Part 2: Universal Shipborne Automatic Identification System (AIS) Operational and Performance Requirements, Methods of testing and required test Results.



51.1) In general, an onboard AIS (see figure 2) consists of:

  • antennas;
  • one VHF transmitter;
  • two multi-channel VHF receivers;
  • one channel 70 VHF receiver for channel management;
  • a central processing unit (CPU);
  • an electronic position fixing system, Global Navigation Satellite System (GNSS) receiver for timing purposes and position redundancy;
  • interfaces to heading and speed devices and to other shipborne sensors;
  • interfaces to radar/Automatic Radar Plotting Aids (ARPA), Electronic Chart System/Electronic Chart Display and Information System (ECS/ECDIS) and Integrated Navigation Systems (INS);
  • BIIT (Built In Integrity Test); and
  • minimum display and keyboard to input and retrieve data.

With the integral minimum display and keyboard unit, the AIS would be able to operate as a stand-alone system. A stand alone graphical display or the integration of the AIS data display into other devices such as INS, ECS/ECDIS or a radar/ARPA display would significantly increase the effectiveness of AIS, when achievable.

51.2) All onboard sensors must comply with the relevant IMO standards concerning availability, accuracy, discrimination, integrity, up-date rates, failure alarms, interfacing and type-testing.

51.3) AIS provides:

  • a built in integrity test (BIIT) running continuously or at appropriate intervals;
  • monitoring of the availability of data;
  • an error detection mechanism of the transmitted data; and
  • an error check on the received data.


51.4) The connection of AIS to external navigational display systems

51.5) The AIS can be connected either to an additional dedicated AIS display unit, and possibly one with a large graphic display, or to an existing navigational system such as radar or an electronic chart but in the latter case only as part of an integrated navigation system.

The connection of AIS to external portable navigational equipment

51.6) It is becoming common practice for pilots to possess their own portable navigational equipment, which they carry on board. Such devices can be connected to shipborne AIS equipment and display the targets they receive.

The connection of AIS to external long-range radiocommunication devices

51.7) AIS is provided with a two-way interface for connecting to long range radiocommunication equipment. Initially, it is not envisaged that AIS would be able to be directly connected to such equipment.

51.8) A shore station would first need to request that the ship makes a long range AIS information transmission. Any ship-to-shore communication would always be made point-to-point, and not broadcast, and once communication had been established, the ship would have the option of setting its AIS to respond automatically to any subsequent request for a ship report from that shore station.

51.9) Users are reminded that the SOLAS regulation V/11.10 provides that the participation of ships in IMO-adopted ship reporting systems shall be free of charge to the ships concerned.




1.) AIS operates primarily on two dedicated VHF channels (AIS1 - 161,975 MHz and AIS2 - 162,025 MHz). Where these channels are not available regionally, the AIS is capable of automatically switching to alternate designated channels.

2.) The required ship reporting capacity according to the IMO performance standard amounts to a minimum of 2000 time slots per minute (see fig. 3). The ITU Technical standard for the Universal AIS provides 4500 time slots per minute. The broadcast mode based on a principle called (S)TDMA (Self-organized Time Division Multiple Access) that allows the system to be overloaded with 400 to 500 % and still provides nearly 100% throughput for ships closer than 8 to 10 NM to each other in a ship to ship mode. In the event of system overload, only targets far away will be subject to drop out in order to give preference to targets close by, that are a primary concern for ship-to-ship operation of AIS. In practice, the capacity of the system is unlimited allowing for a great number of ships to be accommodated at the same time.






(IMO S/N circ.227 giving guidelines on the installation of AIS)


1. General
1.1 Survey
1.2 Documentation

2 AIS Installation
2.1 Interference to the Ship’s VHF Radiotelephone
2.2 VHF Antenna Installation
2.3 GNSS Antenna installation
2.4 Power source
2.5 Synchronization

3. Bridge Arrangement
3.1 Minimum Keyboard and Display
3.2 Pilot plug
3.3 Display system
3.4 Installation of the BIIT (Built-in Integrity Test) function

Dynamic data input
4.1 External Sensors
4.2 Position, COG and SOG
4.3 Heading
4.4 Rate of Turn
4.5 Navigational Status

5. Static Information
5.1 Entered at initial installation of AIS
5.2 Reference point of position
5.3 Ship’s dimensions

6. Long-Range function

Annex 1 Rate of Turn
Annex 2 Type of ship table
Annex 3 Recommended IEC 61162 sentences


The Automatic Identification System (AIS) Class A is defined by IMO and has been made a carriage requirement by the latest revision of SOLAS chapter V. AIS provides information that may be used for the navigation of the ship. It is therefore essential that the information provided by AIS be reliable.

The AIS itself has been standardised by the International Telecommunications Union (ITU) and the International Electrotechnical Commission (IEC) and is subject to type approval. In order to fulfil the reliability requirements of information exchange, care should be taken to ensure that the AIS is correctly installed.

This document contains guidelines for manufacturers, installers, yards, suppliers and ship surveyors. It does not replace documentation supplied by the manufacturer.

The guidelines take into account the following conventions, regulations, instructions and guidelines:

•IMO resolution MSC.90(73) Annex 7, Adoption of amendments to the International Convention for the Safety of Life at Sea, 1974, as amended.

•IMO resolution MSC.74(69) Annex 3, Recommendation on performance standards for AIS.

•ITU Radio Regulations (RR).

•IEC 60092 (series), Electrical Installations on Ships.

•IEC 60533 Electrical and Electronic Installations in Ships - Electromagnetic Compatibility.


1.1 Survey
Surveys on Convention ships should be carried out in accordance with the rules laid down in resolution A.746(18) "Survey Guidelines under the harmonised system of survey and certification", and "Protocol of 1988 relating to the International Convention for the Safety of Life at Sea, 1974, as amended."

1.2 Documentation
For the AIS installation the following drawings shall be submitted:
•Antenna layout
•AIS arrangement drawing

•Block diagram (interconnection diagram)

An initial installation configuration report should be produced during installation and kept on board.


2.1 Interference to the Ship’ s VHF Radiotelephone The AIS shipborne equipment, like any other shipborne transceiver operating in the VHF maritime band, may cause interference to a ship’s VHF radiotelephone. Because AIS is a digital system, this interference may occur as a periodic (e.g. every 20 s) soft clicking sound on a ship’s radiotelephone. This affect may become more noticeable when the VHF radiotelephone antenna is located near the AIS VHF antenna and when the radiotelephone is operating on channels near the AIS operating channels (e.g. channels 27, 28 and 86). Attention should be paid to the location and installation of different antennas in order to obtain the best possible efficiency. Special attention should be paid to the installation of mandatory antennas like the AIS antennas.

2.2 VHF Antenna Installation

2.2.1 Location
Location of the mandatory AIS VHF antenna should be carefully considered. Digital communication is more sensitive than analogue/voice communication to interference created by reflections in obstructions like masts and booms. It may be necessary to relocate the VHF radiotelephone antenna to minimize interference effects.

To minimise interference effects, the following guidelines apply:

  • The AIS VHF antenna should have omnidirectional vertical polarisation.
  • The AIS VHF antenna should be placed in an elevated position that is as free as possible with a minimum of 2 metres in horizontal direction from constructions made of conductive materials. The antenna should not be installed close to any large vertical obstruction. The objective for the AIS VHF antenna is to see the horizon freely through 360°.
  • The AIS VHF antenna should be installed safely away from interfering high-power energy sources like radar and other transmitting radio antennas, preferably at least 3 m away from and out of the transmitting beam.
  • Ideally there should not be more than one antenna on the same level. The AIS VHF antenna should be mounted directly above or below the ship’s primary VHF radiotelephone antenna, with no horizontal separation and with a minimum of 2 m vertical separation. If it is located on the same level as other antennas, the distance apart should be at least 10 m.

2.2.2 Cabling
The cable should be kept as short as possible to minimise attenuation of the signal. Double screened coaxial cables equal or better than RG214 are recommended. All outdoor installed connectors on the coaxial cables should be waterproof by design to protect against water penetration into the antenna cable.

Coaxial cables should be installed in separate signal cable channels/tubes and at least 10 cm away from power supply cables. Crossing of cables should be done at right angles (90°). Coaxial cables should not be exposed to sharp bends, which may lead to change the characteristic impedance of the cable. The minimum bend radius should be 5 times the cable's outside diameter.

2.2.3 Grounding
Coaxial down-leads should be used for all antennas, and the coaxial screen should be connected to ground at one end.

2.3 GNSS Antenna installation

Class A AIS should be connected to a GNSS antenna.

2.3.1 Location

The GNSS antenna should be installed where it has a clear view of the sky. The objective is to see the horizon freely through 360° with a vertical observation of 5 to 90° above the horizon. Small diameter obstructions, such as masts and booms, do not seriously degrade signal reception, but such objects should not eclipse more than a few degrees of any given bearing. Locate the antenna at least three meters away from and out of the transmitting beam of high-power transmitters (S-Band Radar and/or Inmarsat systems). This includes the ship’s own AIS VHF antenna if it is designed and installed separately. If a DGNSS system is included or connected to the AIS system, the installation of the antenna should be in accordance with IEC 61108-4, Ed 1, annex D.

2.3.2 Cabling

To achieve optimum performance, the gain of the antenna pre-amplifier should match the cable attenuation. The resulting installation gain (pre-amplifier gain - cable attenuation) should be within 0 to 10 dB. The coaxial cable between the antenna and the AIS shipborne station connector should be routed directly in order to reduce electromagnetic interference effects. The cable should not be installed close to high-power lines, such as radar or radio-transmitter lines or the AIS VHF antenna cable. A separation of one meter or more is recommended to avoid degradation due to RF-coupling. Crossing of antenna cables should be done at 90° to minimise magnetic field coupling. All outdoor installed connectors on the coaxial cables should be waterproof by design to protect against water penetration into the antenna cable.

2.4 Power source

The AIS should be connected to an emergency power source.

2.5 Synchronization

After installation, the AIS should be synchronised properly on UTC and that position information, if provided, should be correct and valid.

3 Bridge Arrangement

3.1 Minimum Keyboard and Display

The functionality of the Minimum Keyboard and Display (MKD) should be available to the mariner at the position from which the ship is normally operated. This can be by means of the AIS’ internal MKD (integrated or remote) or through the equivalent functionality on a separate display system

3.2 Pilot plug

A pilot input/output port is part of an AIS Class A station. A plug connected to this port should be installed on the bridge near the pilot’s operating position so that a pilot can connect a Personal Pilot Unit (PPU).

The pilot plug should be configured as follows:

  • AMP/Receptacle (Square Flanged (-1) or Free-Hanging (-2)), Shell size 11, 9-pin, Std. Sex 206486-1/2 or equivalent with the following terminations:

- TX A is connected to Pin 1
- TX B is connected to Pin 4
- RX A is connected to Pin 5
- RX B is connected to Pin 6
- Shield is connected to Pin 9

3.3 Display system

If there is navigational equipment capable of processing and displaying AIS information such as ECDIS, radar or an integrated system available on board the ship, the AIS Class A mobile system may be connected to that system via the AIS Presentation Interface (PI). The PI (input/output) should meet the requirements of IEC 61162-2.

The display system can also include the functionality of an MKD, see 3.1.

3.4 Installation of the BIIT (Built-in Integrity Test) function

The AIS requires that an alarm output (relay) be connected to an audible alarm device or the ships alarm system, if available. Alternatively, the BIIT alarm system may use the alarm messages output on the PI, provided its alarm system is AIS compatible.

4 Dynamic data input

4.1 External Sensors

The AIS has interfaces (configurable as IEC 61162-1 or 61162-2) for position, heading and rate of turn (ROT) sensors. In general, sensors installed in compliance with other carriage requirements of SOLAS Chapter V should be connected to the AIS.1 The sensor information transmitted by AIS should be the same information being used for navigation of the ship. The interfaces should be configured as given in annex 3. Interfacing problems might occur if the existing sensors found on board do not have serial (IEC 61162) outputs.

4.2 Position, COG and SOG

GNSS sensors normally have IEC 61162 outputs for position, COG and SOG suitable for directly interfacing the AIS. However, it is important to note that:

  • The Geodetic Datum of the position data transmitted by the sensor is WGS 84 and that an IEC 61162 DTM sentence is configured.
  • AIS is able to process two reference points for its antenna position, one for external and one for an internal sensor. If more than one external reference point is used, the appropriate information needs to be input to the AIS to adjust reference point information.

4.3 Heading

A compass providing heading information is a mandatory sensor input to the AIS. A converter unit (e.g. stepper to NMEA) will be needed to connect AIS if the ship’s compass does not provide an IEC 61162 output. Some ships of less than 500 gross tonnage may not carry a compass providing heading information.

4.4 Rate of Turn

All ships may not carry a Rate-Of-Turn (ROT) Indicator according to resolution A.526(13). However, if a rate-of-turn indicator is available and it includes an IEC 61162 interface, it should be connected to the AIS.

If ROT information is not available from a ROT indicator, the direction of turn may (optionally) be derived from heading information through:

  • The compass itself,
  • An external converter unit (see paragraph 4.3),
  • The AIS itself (see annex 1).

4.5 Navigational Status

A simple means should be provided for the operator to input the ship’s navigational status (e.g. underway using engine, at anchor, not under command, restricted in ability to maneuver, etc) information into the AIS. The AIS may be connected to the ship's navigational status lights. *

*Installation of the AIS does NOT establish a need to install additional sensors above carriage requirements.

5 Static Information

The AIS standards require that certain static, voyage-related, and dynamic information be entered manually, normally by means of the MKD, or by means of IEC 61162 sentences “SSD” and “VSD” via the presentation interface if such provisions exist.

5.1 Entered at initial installation of AIS

Information that should be entered at the initial installation of the AIS includes:·

  • Maritime Mobile Service Identity (MMSI) number
  • IMO vessel number
  • Radio call sign
  • Name of ship
  • Type of ship
  • Dimension/reference for position of the electronic position fixing device (EPFD) antenna (see paragraph 5.2)

Access to MMSI, IMO number and other AIS controls (like power and channel settings) will be controlled, e.g. by password.

The Call Sign, Name of Ship and Type of Ship should be input to the AIS, either manually using the MKD or by means of IEC 61162 sentences “SSD” and “VSD” via the PI. Type of Ship information should be in accordance with the table given in annex 2 (Table 18 from Rec. ITU-R M.1371-1).

For example, a cargo ship not carrying dangerous goods, harmful substances, or marine pollutants; would use identifier “70”. Pleasure craft would use identifier “37”. Note that those ships whose type identifier begins with a “3” should use the fourth column of the table.

Depending on the vessel, cargo and/or the navigational conditions, this information may be voyage related and would therefore need to be changed before beginning or at some time during the voyage. This is defined by the “second digit” in the fourth column of the table.

5.2 Reference point of position

The AIS stores one “external reference point” for the external GNSS antenna position and one “internal reference point” if an internal GNSS is to be used as fallback for position reporting. The locations of theses reference points have to be set during installation using values A, B, C, D; as described in paragraph 5.3.

The external reference point may also be a calculated common reference position.

Additionally, the content of the Ship Static Data (“SSD”) sentence on the PI, including the “reference point for position” is being processed by the AIS, and the AIS’ memory for the “external reference point” is set in accordance with the content of this “SSD” (e.g. used by an INS).

5.3 Ship’ s dimensions

Ship’s dimensions should be entered using the overall length and width of the ship indicated by the values A, B, C, and D in the following figure.

Ship’s dimensions (A+B and C+D) should be identical when entering internal and external reference points.

In the rare case of an EPFD antenna installed in the portside corner of a rectangular bow, the values A and C would be zero. Should this be the case, one of these values should be set to 1 in order to avoid misinterpretation as “not available” because A=C=0 is used for that purpose.

6 Long-range function

The AIS’ long-range function needs a compatible long-range communication system (e.g. Inmarsat-C or MF/HF radio as part of the GMDSS).

If this is available, a connection between that communication system and the Class A mobile unit can be made. This connection is needed to activate the LR function of AIS. Its input/output port should meet the requirement of IEC 61162-2.


Annex 1 - RATE OF TURN

The AIS provides the Rate of Turn (ROT) information to other ships in order to early detect ships manoeuvres. There are two possible parameters indicating turning of a ship derived from two different sensors (see Figure 3: ROT sensor input):
  • the heading from a GYRO or THD and
  • the rotation rate itself from a Rate of Turn- indicator.

If a Rate of Turn Indicator according to resolution A.526(13) is connected, the AIS should use this information to broadcast both direction and value of turn on the VDL. If valid ROT or HDG data is available from other external sources (Gyro, INS,...), the AIS should use this information to broadcast the direction of turn on the VDL, if greater than 5° in 30 s (might also be implemented as 2.5° in 15 s by configuration); the AIS may also derive ROT information from HDG internally for that purpose.

If no ROT information is available, the AIS should transmit default values indicating “not available”. ROT data should not be derived from COG information.

If a ship is not required to carry Turn-Indicator or if external sensor fails, the AIS should react according to following priorities: