AIS stands for 'Automatic Identification System' and is a communication system that operates as a self-organised time slot method on registered channels in the maritime mobile VHF band (channel 1 at 161.975 MHz and channel 2 at 162.025 MHz). It is based on an open, unencrypted protocol used to autonomously send and reveice data, without interaction of marine and operator personnel. Options are provided in addition to this autonomous mode that allow short, safety-related messages to also be sent with human interaction.
The data that is autonomously generated and transmitted to other vessels or to the mainland via broadcasts, is dynamic data such as position, speed and heading, as well as static and voyage related data such as depth or type of ship. The transmission occurs at regular intervals, where the transmission interval depends on the speed and course change of the respective vessel. This data is processed by the receiver and can be visualised on a display, generally an Electronic Chart Display and Information System (ESDIS). Current position data is referenced geographically with the respective ship identification of the AIS station received and displayed on a digital map.
When using AIS, navigation at sea should be safer and the state of the environment preserved as accidents can be prevented through targeted support of navigation tasks. AIS was adopted by the International Maritime Organisation (IMO) as a binding standard in 2000. Since 2002 there has been a mandatory equipment requirement for all ships of the following criteria:
- Vessels over 300 GRT gross tonnage engaged in international voyages
- Vessels over 500 GRT gross tonnage engaged in national voyages
- Vessels over 20 meters in length
- Ships carrying more than 50 passengers on board