Come funziona AIS? IN pratica è un super radar attivo che utilizza due canali VHF, la AIS 1 su 161.975 MHz e la AIS 2 162.025 MHz. Obbligatorio dal 2002 sulle navi passeggeri e sui mercantili oltre le 300 tonnellate, ormai esiste anche una Class B di transponder a basso costo per le imbarcazioni più leggere e da diporto. Inoltre sul mercato per poche decine o centinaia di euro è ormai possibile acquistare apparati solo riceventi (per esempio questo Dolphin Maritime o il NASA AIS Engine o il WeatherDock AG), che permettono di rendersi conto del traffico navale senza comunicare la propria posizione. Su Internet cominciano a essere disponibili dei gateway che visualizzano in tempo reale le mappe AIS di diversi porti e la posizione di migliaia di navi. Suggerisco di dare un'occhiata a Vessel Tracker e AISLive. Quella che segue è una presentazione di AIS tratta dal sito SRT.
SOFTWARE RADIO TECHNOLOGY PLC
US$1 million order received
SRT is pleased to announce that its wholly owned subsidiary, SRT Marine Technology Limited, has received an order for its AIS Class B OEM product worth US$1 million from TCB in China.
AIS is being used by China government agencies to improve safety and security on inland waterways and near coastal regions. It is estimated that China has over 200,000 locally registered vessels who may be required to fit AIS by 2011.
Simon Tucker, SRT’s Group Managing Director said; “AIS is truly a global standard and is being used by authorities around the world to improve maritime safety and security. Having already installed a sophisticated national network of base stations,
China has become one of the leaders in this respect. TCB has been working with us for a number of years and we are confident that the combination of our advanced, low cost technology and TCB’s powerful local market position will lead to further orders in the future. With a potential market of 200,000 units over the next 3 to 4 years China presents another large opportunity for us.”
What is AIS?
AIS is the mariner’s most significant development in navigation safety since the introduction of radar. The system was originally developed as a collision avoidance tool to enable commercial vessels to ‘see’ each other more clearly in all conditions and improve the helmsman’s information about his surrounding environment. AIS does this by continuously transmitting a vessels identity, position, speed and course, along with other relevant information to all other AIS equipped vessels within range. Combined with a shore station, this system also offers port authorities and maritime safety bodies the ability to manage maritime traffic and reduce the hazards of marine navigation.
Due to the great safety benefits offered by AIS, this technology was made compulsory throughout the world in 2002 for all passenger ferries and vessels over 300 gross tonnes. An AIS transponder determines its own position, speed and course using a built in GPS receiver. This information is combined with other important navigation information and automatically communicated between AIS equipped vessels without any user interaction.
AIS transponders on other vessels and coast stations receive this information and use it to build up a live graphical display of traffic in the area. The transponder can be connected to many types of chart plotter or PC charting software using a standard interface protocol. AIS does not require a radar, but can offer similar capabilities and even enhance a radar image if a radar has already been fitted to the vessel.
The range of coverage of the system is similar to a VHF radio. The system also has the advantage that VHF radio signals will travel around bends and over islands giving better coverage than radar or enhancing a radar picture when used together.
Benefits of AIS
See and be seen
A Class B transponder continuously receives information form all Class A and Class B equipped vessels around you and displays this information on your standard chart plotter or PC. At the same time, your Class B will transmit your position to all AIS equipped vessels automatically.
Safety at night and in poor weather conditions
The Class B AIS is a vital navigation tool in poor visibility conditions. The information received from other AIS ‘targets’ provides the user with vital navigation information and the position transmission alerts other vessels to the user’s location.
Combined with radar, AIS gives you the best possible picture of your situation in all conditions.
Position transmission to authorities / nearby vessels in case of emergency.
Graphically view your position in relation to other vessels when connected to suitable display.
Track vessels of interest such as friends/ colleagues.
AIS Classes explained
Two types of AIS transponder are available: Class A and Class B. Despite the huge safety benefits of commercial (Class A) AIS, the cost of this advanced technology has previously been a barrier to introducing AIS to leisure craft and light commercial vessels. To overcome this problem the Class B AIS transponder has been developed to provide all the benefits of AIS in a cost effective, reliable and user-friendly product for users that do not need the comprehensive data required for commercial shipping.
The Class B product has been designed with the light commercial and leisure user’s budget in mind, yet still offers all the advantages of AIS. The device can be easily installed and connected to most chart plotters or PC based navigation software.
AIS receivers are also available; these units will pick up broadcasts from both Class A and Class B AIS transponders but do not transmit their own position. A receiver allows you to see the position of other vessels, however your position will not be visible to them.