A.I.S. Description

Imagine having an electronic chart on your PC screen displaying a coastline.  On the chart are moving icons, each one representing a vessel moving in real time.  Zooming in and out allows the user to have different perceptions of the targets in relation to each other and to the land.  By clicking on an icon (vessel), a list of information is provided for the specific target.  Target information includes name, course, speed, position, type of vessel etc. This possibility exists and we are referring to Automatic Identification System.

AIS technology was developed during the early 90’s for maritime safety purposes under the initiative of the IMO (International Maritime Organisation), who eventually applied the standard internationally.

Today, almost every vessel in the world over 300GT (SOLAS Vessels) carries an AIS class A unit, following respective International and National mandates.  The unit which is connected to other navigational equipment on board a vessel (GPS, radar, compass etc), transmits and receives information every few seconds (name, position, speed, course, etc).

Each transmission is broadcasted on one of two specified VHF frequencies for that purpose.  Nearby ships carrying AIS will receive that transmission and can view all data on their navigational equipment (electronic charts, radar etc) assisting them in making vital decisions in respect to ship movement and collision avoidance.  In other words a captain can see the position of a nearby ship oh his electronic chart, he can also see the course and speed of that ship even if weather conditions, or nightfall, or perhaps an obstacle e.g. a small island do not allow direct or good eye contact.

AIS makes navigation easier especially in high traffic regions such as ports, channels or in heavy weather conditions with low visibility and increasing collision risks.

Recently another IMO specification has allowed the development of the AIS class B unit which is the less costly solution for non mandatory cases (NON SOLAS vessels).      Many small vessels all over the world have installed AIS Class B units and can now “see” and be “seen” by class A and B AIS equipped vessels.

Class B compared to class A AIS has no difference in receiving AIS information and little difference in respect to transmitting.  It can be connected to the vessel’s plotter so a captain can see nearby AIS carrying ships.  Class B units will transmit at intervals between 30 seconds and 6 minutes as opposed to 2 sec and 6 min for class A.  Transmission intervals depend on navigational status e.g. vessel moving, turning, moored etc.   Finally, class A units have transmission priority over class B.

AIS has become a valuable tool for National Agencies around the world in respect to monitoring and managing maritime traffic in various strategic areas (Ports, waterways, canals, borders ect) with the use of land based AIS transponders (AIS Base Stations). In the past decade AIS shore based networks have been developed and installed to cover the above requirement for organisations such as Maritime Authorities Ports, Port Police and the Maritime Industry in General.