AIS is an automatic identification system that was introduced by the UN's International Maritime Organisation (IMO) in order to increase the safety of ships and the environment, and to improve traffic monitoring and maritime traffic services.
AIS is an important tool for navigators on vessels and for the maritime traffic control centres that monitor and regulate the traffic.
Since February 2005 the Norwegian Coastal Administration has had a land-based network of AIS basestations in Norway.
AIS is used:
- in ship-to-ship situations to prevent collisions,
- as a tool for coastal states for obtaining information on a ship and its cargo, and
- as a tool for the maritime traffic control centre services for ship-to-shore purposes.
An AIS transponder on board a ship shall automatically, and with the required accuracy and update rate, provide other ships and coastal state authorities with information from the ship.
Such information is:
- Dynamic (position, course, speed)
- Static (identity, vessel type, dimensions)
- Details on the sailing (destination, estimated time of arrival, cargo, draught)
This information is packaged into standardised messages and transmitted over internationally reserved channels in the maritime VHF band. Static and sailing-related information is transmitted every 6th minute or when the data changes. Dynamic information is transmitted at an update rate ranging from 3 minutes to 2 seconds, depending on the vessel's speed and course change.
The AIS range is limited by the VHF range, which is determined primarily by the height of the antenna. The typical range from a vessel at sea is 20 nautical miles.
AIS information is also made available to other government agencies with responsibilities and authority related to ports and ship traffic in Norwegian waters.
AIS as a supplement to radar
On board a ship the AIS information received from other ships will be a supplement to radar-based information. Other ships that are equipped with AIS can be detected and identified. AIS uses a longer wavelength than radar and provides therefore better coverage behind obstacles as long as the height of the terrain is not too great. In addition, AIS can help distinguish ships that would otherwise blend in with land or other radar echoes.
In addition to AIS transponders for use on board ships that are encompassed by the IMO SOLAS Convention from 1974 (Class A AIS), AIS transponders have also been developed for use on land (AIS base stations), for beacons and markers, on board pleasure craft (Class B AIS), and on board rescue helicopters and planes.
Operative use of AIS data
The AIS network will primarily be used by the Norwegian Coastal Administration's maritime traffic control centres as a sensor for information on the vessel's position, course, speed and identity. The Norwegian Coastal Administration's maritime traffic controllers can also use the AIS network to transmit safety-related messages to vessels. In certain cases a traffic controller can use the AIS network to request AIS messages from vessels or to reduce the reporting interval.
The Norwegian Coastal Administration currently operates five maritime traffic control centres located at Horten, Brevik, Kvitsøy, Fedje and Vardø. The maritime traffic control centres engage in civil traffic monitoring, traffic regulation, traffic control and other maritime traffic services. The purpose is to increase safety and the navigability of fairways with relatively congested and complex traffic patterns. The control centre in Vardø has an area of responsibility in waters that are not covered by the four other control centres and out to the territorial limit, with a special focus on ships that are carrying hazardous and pollutive cargo in transit along the Norwegian coast. Together with radar, AIS provides traffic controllers with a complete picture of the traffic situation within the control centres' area of responsibility.
The Norwegian Coastal Administration also uses the AIS network for purposes other than pure traffic monitoring. For oil pollution preparedness, access to AIS data quickly provides information on the traffic situation surrounding a reported oil spill. Pilot boat skippers and pilots use AIS information to simplify the planning of pilot assignments. In addition, the Norwegian Coastal Administration uses AIS data for transport planning in fairways and for the preparation of statistics on traffic movements.
The Norwegian Coastal Administration has access to AIS data from national AIS networks in countries around the Baltic Sea and the eastern part of the North Sea based on international cooperation agreements. Cooperation has also been established with oil companies on the Norwegian continental shelf for the exchange of data from AIS receivers on offshore installations. Access to AIS data from offshore installations provides coverage for up to 100-150 nautical miles from the coast in the relevant areas.
Data from the AIS network is distributed to other government agencies:
- Norwegian Armed Forces
- Joint Rescue Coordination Centres
- Norwegian Maritime Directorate
- Climate and Pollution Agency (KLIF)
AIS in combination with other systems AIS provides dynamic ship information (position, course, speed) with a high update rate and accuracy. The static (identity, vessel type, dimensions) and sailing related (destination, ETA, cargo, draught) information from AIS is more limited in scope and can in many instances be insufficient. By combining AIS data with other maritime information systems, the quality of static and sailing related information on a ship can be significantly improved.
A combination with data from the reporting system SafeSeaNet Norway (SSNN) can provide information on the vessel's destination and estimated time of arrival, and whether the vessel is carrying hazardous or pollutive cargo. This is, for example, important information for the Norwegian Coastal Administration's maritime traffic control centres and oil pollution preparedness. In addition, SSN information provides information on the number of persons on board, which is important information for search and rescue operations.
A combination of data from ship registers through SSN will provide more exact information on the actual vessel than can be obtained from AIS. This information includes, for example, tonnage, age, class, ownership, machinery, equipment, cargo capacity and dimensions. There are also photographs of the relevant vessels in some instances.
Use of historic AIS data
The Norwegian Coastal Administration will use historic AIS data to prepare statistics on maritime traffic along the coast. When the AIS statistics are prepared, the AIS data will be combined with data from other maritime information systems. Safety measures such as marking, sailing regulations or extra monitoring can be planned on a better basis than before with the AIS statistics. The knowledge that historic AIS data provides on ship traffic will give the Norwegian Coastal Administration an opportunity to improve its planning and facilitate fast, safe and efficient sea transport.
Historic AIS data is used to control the legitimacy of vessels and their use of the coast, and applies, for example, to the control of compulsory pilotage, the pilot exemption certificate regulations and the follow-up of the notification regime. Historic AIS data is also a good tool for the reconstruction and documentation of the traffic situation after accidents at sea.