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Tracking Ships Using Automatic Identification System

written by: Raunekk • edited by: Lamar Stonecypher • updated: 2/7/2010

Keeping track of ships sailing at sea has become an important aspect of maritime navigation these days. The Automatic Identification system (AIS) is a device which not only helps in tracking ships at sea, but also helps in avoiding accidents and traffic congestion.

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    Introduction to AIS

    Increasing ship traffic at sea has led to several problems both near the ports and at high seas. Many accidents and collisions of ships in the past have been a result of lack of information of the nearby ship and misguiding instructions from port authorities. These incidents have been the main reason for the invention and usage of ship tracking devices. Moreover, many ship owners also need to keep a track of the cargo they are transporting. The ship tracking devices helps in serving these needs also.

    The automatic identification system is one such versatile ship tracking device. An automatic identification system, as the name suggests, automatically helps in procuring detailed information of any ship at sea. A fully automatic system, automatic identification system (AIS) provides all the information regarding a particular ship to the nearby ships and also to the coastal authorities.

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    How does AIS Work?

    Automatic identification system (AIS) runs on the basic principle of transferring data electronically over a radio wave frequency. An AIS device consists of very high frequency (VHF) transmitters and receivers. The transmitter and receiver are attached to the ship’s display and sensors systems through a communication link. In order to receive exact information of other ships and also to send its own, the AIS also has a Global positioning system (GPS) which is connected to a satellite. The GPS can be an internally attached device or a separately fitted system. AIS is also connected to all the other systems of the ship and that is how it receives ship’s details and sends them across to other ships.

    AIS is also known as the most important and safest navigation system on board a ship. This is because AIS runs automatically and continuously, sending and receiving information regardless of the ship’s position with respect to the shore. Moreover, though only one channel is required to transfer the details, AIS also has a secondary channel to prevent any kind of interference or loss of information.

    Also, as each of the ships has its own AIS system, there are high chances of an increase in traffic and congestion in the channels. However, this never happens. The AIS system has an automatic system that resolves the contention between itself and other stations in spite of rise in load. This is possible because each station has its own transmission slot. The AIS systems are so designed that the transmission slots are automatically assigned to a particular station on the basis of the traffic history of the station. Each of the slots is of 26.6 milliseconds, which means that each station can transmit information during that much time before the chance goes to the next station. For this, there are in total 2,250 slots. The information sent from a station in a particular time slot serves as a reference for the next coming information which gets stored in some other randomly organized slot. The information received and transmitted through these slots is immediately transferred to any vehicle which comes in the same radio range. Thus the 2250 slots all together serve as a common network for providing information of all the ships coming under particular frequency channel.

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    What Information can be Transferred?

    Automatic indication system helps in transferring each and every detail regarding a particular ship. It helps in procuring details such as a ship’s name, speed, position, direction, rate of turn, destination etc. It also helps in getting physical dimensions of the ship such as length, breadth, tonnage, beam, and draft. All these items of information are directly sent to the display system of the ship, wherein each and every detail is continuously displayed in real time.

    All these details are extremely helpful in avoiding ship collisions, reducing and monitoring traffic, assisting in navigation, search and rescue operations, and in investigation and research. Thus, AIS helps not only in tracking the ships but also in avoiding many unfavorable situations.

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    Image Credits

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