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John Macdonald
Automatic Identification System (AIS) equipment is to be implemented as a mandatory carriage requirement under SOLAS for newly constructed ships from 1 July 2002 and progressively fitted to other types and sizes of ships up to 1 July 2008.[1]
It has long been realised that an automatic reporting device (‘transponder’) fitted to a ship would be beneficial to the safety of navigation and the identification and monitoring of maritime traffic. AIS is such a broadcast ‘transponder system’ capable of sending information such as ship identification, position, course, speed (and more) to other ships, aircraft and to shore. The International Maritime Organization (IMO) has defined its operational requirements.
AIS can handle multiple reports (over 4000 per minute) at rapid update rates (every 2 seconds) and uses the maritime VHF band for the transmission and reception of its messages. The channels allocated for worldwide use with AIS are AIS1 (161.975 MHz.) and AIS 2 (162.025 MHz.). Provision is also made for administrations to designate ‘regional’ frequency channels for AIS in coastal or port areas where the global channels are unavailable.
AIS contributes to and enhances the safety of life at sea, the safety and efficiency of navigation and the protection of the marine environment. SOLAS Chapter V, Regulation 20, states that
AIS shall:
• Provide automatically to appropriately equipped shore stations, other ships and aircraft, information, including the ship’s identity, type, position, course, speed, navigational status and other safety-related information;
• Receive automatically such information from similarly fitted ships;
• Monitor and track ships; and
• Exchange data with shore-based facilities.
AIS will become an important supplement to shore-based traffic monitoring and surveillance sensor systems and data received via AIS will enhance the quality of information available to all users.
AIS was conceived to assist vessels operating in a Vessel Traffic Service (VTS) area or Traffic Separation Scheme (TSS) while ensuring that shore authorities have the ability to easily identify vessels, to automatically receive from them large amounts of useful information and to communicate with them using the AIS functionality. Information received and transmitted through AIS enables shore authorities to better monitor and organise the traffic in the particular area of the VTS or TSS and to provide related information, assistance or transmit advice to the vessel.
AIS applications will provide benefits for the VTS operations including:
• Vessel identity and other static and voyage related information are automatically available to the VTS operator;
• Additional information such as heading, course and speed over ground, rate of turn and ship dimensions is available to the VTS operator in near real time;
• The extension of VTS and participating vessels surveillance beyond normal radar coverage and within radar shadow areas;
• Radar tracking integrity problems, such as target swapping and degradation due to sea clutter and weather, are non-existent;
• Enhanced navigation assistance capability through precise navigation monitoring and ship path prediction;
• The potential for reduced operator workload in voice communications;
• The ability to send short text messages from the VTS to one vessel or several vessels.
AIS will have an immediate impact on VTS operations. Probably the greatest advantage will be the improved information and the immediate identification of AIS equipped vessels. However, some VTS centres may have to update their equipment in order to facilitate the reception of AIS data. Computer processors may have to be upgraded in order to cope with the increase in received data and filtering systems may be needed to allow for selective display of information.
There will have to be good correlation between the radar signal of a target and its AIS signal, the lack of which may introduce doubt as to the exact position of the vessel concerned. For some years yet there will be many vessels not fitted with AIS that will need to be treated in the conventional manner. An unknown factor at present is the effect of AIS on human resources.
AIS has been designed to allow shore authorities to monitor vessels operating within their coastal waters, designated mandatory ship reporting system (SRS) area or EEZ and even outside VHF coverage areas using the Long Range mode. Any reports likely to be required from shipping will normally be included in the standard static, dynamic and voyage related messages.
This will ensure a quicker response to emergencies and will create the ability for coastal state to assess the navigational requirements or improvements to navigational safety in such areas. Much value can arise from such monitoring, including better traffic routeing, port and harbour planning and more safety-related information exchange.
A portable system has been developed, primarily to provide marine pilots with the capability to carry onboard a transponder when piloting ships not fitted with AIS. Housed in a ruggedised case, it contains the transponder equipment (including a GPS or DGPS receiver card) batteries and in-built VHF and GPS/DGPS antennas. It has a wireless link and a laptop PC fitted with ECS and AIS display software.
A further application of AIS beyond the more obvious ship-ship and ship-shore role is the use of an AIS transponder as an Aid to Navigation (AtoN). When positioned at a significant geographic point or danger to navigation the equipment can provide information and data that would serve:
• to complement or replace an existing fixed or floating aid to navigation, providing identity, performance and position status and other information such as real time tidal height, tidal stream and local weather;
• as a replacement for radar transponder beacons (racons) at certain sites, provide longer range detection and identification in all weather conditions, and
• as a data gathering tool, providing extensive information on all AIS fitted shipping traffic passing within VHF range of the shore/offshore site.
AIS is a major emerging technology in the maritime world. It will bring significant benefits when applied to VTS but, like many other equipments, it has limitations that will need to be carefully managed. The amount of data potentially available via AIS poses a problem in itself, and its effective use will demand adequate training and new procedures.
AIS, when integrated into a VTS has the potential to enhance both safety and efficiency, in that it will provide VTS operators with more accurate and more comprehensive data than radar. It will also reduce manual operator function and activity on some marine voice circuits. However, it will not render obsolete either radar or voice communications.
It is important that maritime authorities make efforts now to become aware of the great potential of AIS to support navigational safety and efficient traffic management.
• Performance Standards for AIS – Annex 3 to IMO Resolution MSC.74 (69)
• Technical Characteristics – ITU-R Recommendation M.1371-1
• VHF Channel Allocation – ITU-Radio Regulations, Appendix S 18, Table of Transmitting Frequencies in the VHF Maritime Mobile Band.
• Type Approval Test Specifications – IEC Test Standard 61993-2
[1] As part of their submission to the IMO Maritime Safety Committee (MSC) Working Group on Maritime Security (11-15 February 2002) the United States proposed that the implementation of the mandatory carriage of AIS under SOLAS be advanced to a date not later than 01 July 2004. Accelerated implementation of AIS was again discussed at MSC 75 (May 2002) and further discussion referred to the IMO International Conference on Maritime Security, to be held in December 2002.
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URL: http://www.austlii.edu.au/au/journals/MarStudies/2002/14.html