AIS ( Automatic Identification Systems )

General AIS is a new and untried system, but with the potential to make a significant contribution to safety. It is particularly important therefore that during the early years of implementation its potential is fully assessed by mariners, taking full account of the MCA Guidance and the IMO Guidelines. The MCA will welcome feedback on the use of AIS from ships or companies. Regulation 19.2.4 lays down the timetable for fitting AIS to ships in the given categories. The implementation dates are summarised in the following table: AUTOMATIC IDENTIFICATION SYSTEMS – IMPLEMENTATION Applies to:  All ships 300 gt. and upwards on international voyages or calling at a port of a Member state of the EU All passenger ships, including High Speed Craft, irrespective of size or of 300 gt. and upwards if engaged in domestic trade. TYPE OF VESSEL DATE BY WHICH AIS MUST BE FITTED 1. Ships constructed on or after 1 July 2002 (“new ships”) Date of build 2. Ships constructed before 1 July 2002 (“existing ships”): 2.1 Passenger ships 1 July 2003 2.2 Tankers 1st survey for safety equipment on or after 1 July 2003 2.3 Ships other than tankers or passenger ships of 300 gt and upwards but less than 50,000 gt engaged on international voyages 1 July 2004 2.4 Ships other than tankers or passenger ships of 50,000 gt. or more 1st survey for safety equipment on after 1 July 2004 or by 31 December 2004, whichever occurs earlier 2.5 Ships other than tankers or passenger ships 10,000 – 49,999 gt not engaged on international voyages 1 July 2005 2.6 Ships other than tankers or passenger ships 3000 – 9999 gt not engaged on international voyages 1 July 2006 2.7 Ships other than tankers or passenger ships 300 – 2999 gt not engaged on international voyages 1 July 2007 NOTE: The implementation dates in the above table were reviewed by IMO in December 2002. If the proposals are accepted in January 2004 the dates in the new 2.4 will apply. The EU Traffic Monitoring Directive 2002/59/EC also extends the requirements to ships calling at a port of a Member State of the Community i.e.those on domestic voyages, but the original dates in 2.4, 2.5 and 2.6 apply to domestic voyages and passenger ships of less than 300 gt are exempted.

AIS - MCA GUIDANCE

AIS has the potential to contribute to the safety of navigation and improve the monitoring of passing traffic by coastal states, however it is new equipment and has not yet been evaluated on a global scale. Mariners should therefore take careful note of the following notes and the IMO Operational Guidelines which follow particularly bearing in mind the limitations of the equipment. USE OF AIS IN SHIP REPORTING 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. USE OF AIS IN NAVIGATION AIS is designed to be able to provide additional information to existing Radar or ECDIS displays. Until the optimum display modes have been fully evaluated and decided upon internationally AIS will comprise “stand alone” units without integration to other displays. AIS will provide 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.

AIS – IMO RESOLUTION A.917 (22) AUTOMATIC IDENTIFICATION SYSTEMS (AIS)

GUIDELINES FOR THE ONBOARD OPERATIONAL USE OF SHIPBORNE AUTOMATIC IDENTIFICATION SYSTEMS (AIS)0

THE ASSEMBLY, 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. ANNEX GUIDELINES FOR THE ONBOARD OPERATIONAL USE OF SHIPBORNE AUTOMATIC IDENTIFICATION SYSTEMS (AIS) PURPOSE 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.

CAUTION 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. OBJECTIVES OF AIS 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. DESCRIPTION OF AIS 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. AIS INFORMATION SENT BY SHIPS 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 Static: MMSI (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 Dynamic: 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 ...is 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. Confidentiality 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. OPERATION OF AIS ON BOARD OPERATION OF THE TRANSCEIVER UNIT Activation 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, the AIS may be switched off. This might be the case in sea areas where pirates and armed robbers are known to operate. Actions of this nature should always be recorded in the ship’s logbook together with the reason for doing so. 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. DISPLAY OF AIS DATA 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. Symbols 30.) The user should be familiar with the symbology used in the graphical display provided. INHERENT LIMITATIONS OF AIS 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. USE OF AIS IN COLLISION AVOIDANCE SITUATIONS 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. ADDITIONAL AND POSSIBLE FUTURE APPLICATIONS AIS IN VTS OPERATIONS 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. MANDATORY SHIP REPORTING SYSTEMS 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. AIS IN SAR OPERATIONS 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. AIDS TO NAVIGATION 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. AIS IN AN OVERALL INFORMATION SYSTEM 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. REFERENCE DOCUMENTS 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. DESCRIPTION OF AIS COMPONENTS 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. CONNECTIONS 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.

ANNEX 2 TECHNICAL DESCRIPTION

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.