Automatic identification system
The automatic identification system (AIS) is an automatic tracking system that uses transponders on ships and is used by vessel traffic services (VTS). When satellites are used to detect AIS signatures, the term Satellite-AIS (S-AIS) is used. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport.
It is a ship born transponder system capable of broadcasting continuously using the VHF Marine band, information about the ship.
1)Safety of life at sea
2)Safety and efficiency of navigation
3) Coastal surveillance
4) The protection of the marine environment
Range:20-50Nm depending on antenna height
AIS operates principally on two dedicated frequencies or VHF channels dedicated frequencies or vhf channels:
1)AIS 1: WORKS ON 161.975MHz -Channel 87B( simplex for ship to ship)
2)AIS 2: WORKS ON 162.025MHz-Channel 88B( duplex for ship to shore)
It uses self-organization time division multiple(STDMA) access technology to meet the high broadcast rate. This frequency has a limitation of line of sight which is about 40 miles or so.
Limitations of AIS
1) the accuracy of information received is only as good as the accuracy the AIS information transmitted.
2) position received on the AIS display might not be referred to the WGS 8 datum.
3) Over reliance on the AIS can cause complaints on the part on the part of the officer of watch.
4) Users must be aware that erroneous information might be transmitted by the AIS from another ship.
5) Not all ships are fitted with AIS.
6) The officer of the watch must be aware that AIS if fitted, might be switched off by a certain vessel thereby navigating information that might have been received from ship.
7) it could not be prudent for the officer of the watch to assume that the information received from other ships might not be fully accurate and of precision that might be available on own vessel.
Advantages of AIS over Radar (might come in the exam)
- No target swapping .
- No Blind Sector .
- Not affected by weather.
- Real time data (no delay for data in radar ) .
- Identification of target with additional detail .
Ship’s data content
Static info- Set on installation(transmitted every 6 hours on request).
1) NAME, CALL SIGN
2) IMO,MMSI NUMBER
3) LENGTH, BEAM
4) LOCATION OF POSITION FIXING ANTENNA
(Depends on speed and course alterations and automatically updated)
1) POSITION, UTC TIME
2) COG, HEADING
Navigational statue(underway, at anchor, NUC,aground).
VOYAGE RELATED INFO(every 6 minutes, when data is amended or on request)
-Destination and ESTIMATED TIME OF ARRIVAL
-Route plan(master’s discretion)
Number of persons on board
Either to specified ships or all ships, relevant to the safety of navigation, danger messages – as short as possible normally sent by UTS.
Text messages could also be sent using sent using this
Sleeping target-only presence of vessel indicated
Selected target-CLOSEST POINT OF APPROACH AND TIME TO CLOSEST POINT OF APPROACH VALUES
Lost target-preset range alarm will be given.
State and boys related data every 6 minute or on request(AIS responds automatically, without user action
Dynamic info- dependent on speed and Course alteration
At anchor 3 minute
Additional information (might be out of syllabus for year 2018-2019)
- Collision avoidance
- AIS was developed by the IMO technical committees as a technology to avoid collisions among large vessels at sea that are not within range of shore-based systems. The technology identifies every vessel individually, along with its specific position and movements, enabling a virtual picture to be created in real time. The AIS standards include a variety of automatic calculations based on these position reports such as Closest Point of Approach (CPA) and collision alarms.
- Fishing fleet monitoring and control
- AIS is widely used by national authorities to track and monitor the activities of their national fishing fleets. AIS enables authorities to reliably and cost-effectively monitor fishing vessel activities along their coast line, typically out to a range of 100 km (60 mi), depending on location and quality of coast based receivers/base stations with supplementary data from satellite based networks.
- Maritime security
- AIS enables authorities to identify specific vessels and their activity within or near a nation’s Exclusive Economic Zone. When AIS data is fused with existing radar systems, authorities are able to differentiate between vessels more easily. AIS data can be automatically processed to create normalized activity patterns for individual vessels, which when breached, create an alert, thus highlighting potential threats for more efficient use of security assets. AIS improves maritime domain awareness and allows for heightened security and control. Additionally, AIS can be applied to freshwater river systems and lakes.
- Aids to navigation
- The AIS aids to navigation (AtoN) product standard was developed with the ability to broadcast the positions and names of objects other than vessels, such as navigational aid and marker positions and dynamic data reflecting the marker’s environment (e.g., currents and climatic conditions). These aids can be located onshore, such as in a lighthouse, or on water, platforms, or buoys. The U.S. Coast Guard has suggested that AIS might replace racon (radar beacons) currently used for electronic navigation aids.AtoNs enable authorities to remotely monitor the status of a buoy, such as the status of the lantern, as well as transmit live data from sensors (such as weather and sea state) located on the buoy back to vessels fitted with AIS transceivers or local authorities. An AtoN will broadcast its position and Identity along with all the other information. The AtoN standard also permits the transmission of ‘Virtual AtoN’ positions whereby a single device may transmit messages with a ‘false’ position such that an AtoN marker appears on electronic charts, although a physical AtoN may not be present at that location.
- Search and rescue
- For coordinating on-scene resources of a marine search and rescue (SAR) operation, it is imperative to have data on the position and navigation status of other ships in the vicinity. In such cases, AIS can provide additional information and enhance awareness of available resources, even if the AIS range is limited to VHF radio range. The AIS standard also envisioned the possible use on SAR aircraft and included a message (AIS Message 9) for aircraft to report their position. To aid SAR vessels and aircraft in locating people in distress, the specification (IEC 61097-14 Ed 1.0) for an AIS-based SAR transmitter (AIS-SART) was developed by the IEC’s TC80 AIS workgroup. AIS-SART was added to Global Maritime Distress Safety System regulations effective January 1, 2010.
- Accident investigation
- AIS information received by VTS is important for accident investigation since it provides accurate historical data on time, identity, GPS-based position, compass heading, course over ground, speed (by log/SOG), and rates of turn, rather than the less accurate information provided by radar. A more complete picture of the events could be obtained by Voyage Data Recorder (VDR) data if available and maintained on board for details of the movement of the ship, voice communication and radar pictures during the accidents. However, VDR data are not maintained due to the limited twelve hours storage by IMOrequirement.
- Ocean currents estimates
- Ocean surface current estimates based on the analysis of AIS data have been available from French company, e-Odyn, since December 2015.:
- Infrastructure Protection
- AIS information can be used by owners of marine seabed infrastructure, such as cables or pipelines, to monitor the activities of vessels close to their assets in close to real time. This information can then be used to trigger alerts to inform the owner and potentially avoid an incident where damage to the asset might occur.
- Fleet and cargo tracking
- Internet disseminated AIS can be used by fleet or ship managers to keep track of the global location of their ships. Cargo dispatchers or the owners of goods in transit can track the progress of cargo and anticipate arrival times in port.