IMO Resolution MSC. 74(69) defines AIS as facilities dedicated for increasing of safety of navigation, environment protection and increasing of efficiency of Vessel Traffic Systems (VTS).

Chapter V of SOLAS Convention obligates some ships to be equipped by AIS facilities as early as since 1-st of July, 2002. All ships should be equipped by AIS since 2008.

The main idea of AIS in modern understanding is based on the following work algorithm:

Own position and motion parameters of each ship are determined by Global Navigation Satellite System;

Own ship's identification, position data and motion parameters are automatically and periodically transmitted to all other ships and coast centers; all transmissions are synchronized with each other by means of special algorithm;

Each ship and coast center receives identification data about positions and motion data of all ships situated within VHF radio coverage area;

Received position and motion data of ships situated within VHF radio coverage area are indicated and cyclically updated on ship and coast electronic cartographic aids;

Differential correction data for GPS and GLONASS satellite navigation systems are transmitted by coastal center to the ships, thus increasing an accuracy of position determination;

All participants can exchange by short messages concerning safety which are indicated on the displays of AIS transponders or operator terminals.

The following elements are included into the system for execution of above listed functions:

• AIS transponder, consisting of special VHF transceiver, interface to ship navigation sensors sending position data, course, velocity and interface to navigation aids for display of information such as ARPA and ECDIS.
• Ship AIS operator workplace may be included to ship set or missed.

• One or several AIS transponders situated on the base stations. Transponders can be remotely controlled by control center.
• System server which controls all hardware of AIS system.
• Coast AIS operator workplace (one or more) for system control and display of information.
• GPS/GLONASS differential station which forms differential correction data (desirable, not obligatory).