Theo Quy định 19 đoạn 2.4 Chương V của SOLAS 1974 (IMO), đã sửa đổi, yêu cầu tất cả các tàu có tổng dung tích 300 trở lên chạy tuyến quốc tế, tất cả tàu hàng có tổng dung tích 500 trở lên chạy tuyến quốc tế và tất cả các tàu khách không kể kích thước phải lắp đặt hệ thống nhận dạng tự động (AIS). IMO cũng đã đưa ra khuyến cáo về một lộ trình lắp đặt AIS trên các tàu chỉ định từ nay đến 2008. Đến nay đã có nhiều tàu lắp đặt thiết bị AIS.
AIS GEMAIS AIS Automatic Identification System The AIS transponder is an onboard system operating in the VHF marine band, capable to transmit ship’s information such as ID, position, course, direction, origin, vessel type, draft, freight (especially if dangerous), etc General The collection of cinematic data of the vessel is mainly based on the navigation control by satellite global positioning systems (e.g GPS / DGPS), suitable both in narrow waterways and in open sea This technology allows the automatic position dispatch of the position and of the other information relevant to the vessel in a reliable way and with affordable costs, joining a GPS receiver unit and a VHF radio transceiver operating within the band assigned to AIS systems and compliant with the ITU-RM.1371 recommendation These devices are both included in the AIS transponder which, with reference to Fig 1, fully performs the function of data collection through GPS, communication through VHF radio and data distribution to the external presentation units, both local and remote The system can forward up to 2000 reports per minute and update them every seconds, and exploits the “Self-Organizing Time Division Multiple Access” (SOTDMA) technology to allow high data exchange rate and ensure ship-to-ship operation The system is also compatible with the “Digital Selective Calling Systems”, thus allowing to the land based GMDSS (Global Maritime Distress and Safety System) to establish in a cheap way the operation of the AIS channel and to identify and track the vessels equipped with the transponder Operation mode The main information, like position and speed, is normally provided by the Global Positioning System (GPS, optionally DGPS) The other information, such as direction, SOG (Speed Over Ground), Rate of Turn, Angle of Heel, roll and pitch, destination and ETA (Estimated Time of Arrival), can be provided by the sensors onboard the vessels themselves The AIS transponder normally works in an autonomous and continuous way, regardless if it is installed in open sea, on the coastline or in the hinterland The used frequencies, 9.6 Kb GMS in FM with channels spacing 12.5 KHz or 25 KHz, are prescribed by the ITU-R 1084-2 recommendation and use an HDLC protocol Though only one channel is strictly necessary, each station transmits and receives on several channels in order to avoid interference problems and allow the channels to be reallocated without losing the connection with the other vessels The AIS provides for the resolution of the problems due to the conflict of two or more connections, thus preserving the integrity of the communication also in overload conditions Every station sets its transmission slot based on the traffic chronology and on the knowledge about the future actions of the various stations A position report of an AIS station occupies one over 2250 transmission slots every 60 seconds The AIS stations are constantly synchronized with each-other and avoid the overlapping of the slots; the selection of the transmission slots by each station is random within a defined time span It is also possible to send text messages both ship-to-ship and ship-to-shore The operator composes a text message, inclusive of the addressee; the AIS transponder recognizes the dispatch request and puts the message in the suitable format for the following transmission All the ships within the area controlled by a shore station of the AIS will be able to exchange messages The AIS transponder decides automatically when to send the text message Foreword Within the scope of the management and control of the maritime traffic from land control centers for accident prevention and navigation safety it’s today growing the demand for technically advanced devices, to provide always better performances in terms of navigation prediction (both onboard and in the shore control sites) and capability and speed in the information distribution Considering that the management of the operations at sea is also influenced by the local situation and by the risks involved in the marine activities at whatever level, the AIS system stands as a technologically advanced tool for the safety of the life at sea and for the control of vessel traffic, in full cooperation / integration with the traditional devices such as video / audio radiocommunication as well as with the most advanced systems such as VTMIS (Vessel Traffic Management and Information System), allowing a complete and detailed view of the overall situation within a wide area under surveillance As a matter of fact, under the acronym “AIS” is more correctly included the whole set of processors, equipment, facilities, personnel, software and procedures cooperating in order to classify, organize, evaluate, process, compact, store and retrieve data and information relevant to the navigation and annexed activities, with the human intervention reduced to a minimum The AIS is an efficient tool to exchange the positioning data among the participant naval units and the land control centers and represent them on a suitable display; it has the value to enhance the level of navigation safety for all the involved vessels, providing an adequate coverage also beyond the VTS range, allowing the radio bidirectional communication both in the ship-to-ship and ship-to-shore mode As an information system, the AIS can be split into basic activities: - information collection - information transmission - information presentation The main elements included in the information, as for example: - ship’s name - ship’s position - ship’s course - ship’s speed are gathered from the onboard sensors, forwarded and displayed on the desired device (ARPA radar, laptop PC with charting facility, IMO compliant ECDIS system, etc.), according to the user requirement Fig Data presentation on an “ad hoc” device Fig shows the basic elements of the AIS Ship’s cinematic data collection and translation in the AIS sentence format Initialization and control of the data flow of the AIS sentences among the participant units (ship-to-ship, ship-to-shore) It is straightforward to integrate the AIS technology in a VTS (Vessel Traffic System) or in its more complex version VTMIS (Vessel Traffic Management and Information System) An AIS-based VTS allows to considerably enhance the performance in terms of awareness of the situation being and data processing, with great advantage for the activities of decision-making for the assistance to the sailors during navigation Fig The contribution of the AIS to the VTS is sketched in Fig Installation of the AIS transponder According to the IMO requirements for AIS, the transponder is or will become mandatory onboard the following vessels Type of ship All new-build ships New cargo ships New passenger ships Existing passenger ships Existing tankers Existing ships Existing ships Existing ships Existing ships Existing ships Tonnage >300 >500 ALL ALL ALL >50000 10000 to 50000 3000 to 10000 300 to 3000 ALL Voyage International Non-international International International International International International International International Non-international Date 2002 2002 2002 2003 2003 2004 2005 2006 2007 2008 Transmitted information: General specifications: Static - IMO number - Caller identification and name - Length and orientation - Type of ship - Antenna location onboard (bow or aft) Power consumption: Power supply requirements: Default frequencies: AIS1 AIS2 DSC channel 70: Operating temperature: Storage temperature: Environmental conditions: Built-in GNSS: 161.975 MHZ 162.025 MHZ 156.525 MHz from -15 °C to +55 °C from -20 °C to +70 °C as per IEC 60945 Optional GLONASS/GPS AIS/DSC Transmitter: Power output: Frequency range: Antenna output impedance: 12.5 W or 2.0 W 156.025 - 162.025 MHz 50 Ω TDMA Receivers: Sensitivity: Frequency range: Channel spacing: Modulation: Data rate: Frequency stability: (PER) < 10% at -107 dBm (25kHz) 156.025 - 162.025 MHz 12.5 or 25 kHz GMSK 9,600 bits/s < ± 1ppm DSC Receiver: Sensitivity: Frequency range: Channel spacing Modulation Frequency stability BER