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The Automatic Identification System (AIS) is a system used by ships and Vessel Traffic Services principally for identification and locating vessels. AIS helps to resolve the difficulty of identifying ships when not in sight (e.g. in fog, at distance, etc.) by providing a means for ships to exchange identification, position, course, speed, and other ship data with all other nearby ships and VTS stations. It works by integrating a standardized VHF transceiver system with an electronic navigation system, such as a LORAN-C or Global Positioning System receiver, and other navigational sensors on board ship (gyrocompass, rate of turn indicator, etc.). Image File history File links OperationsSpecialistVTS.jpg Summary A U.S. Coast Guard Operations Specialist using AIS and RADAR to manage vessel traffic. ...
Image File history File links OperationsSpecialistVTS.jpg Summary A U.S. Coast Guard Operations Specialist using AIS and RADAR to manage vessel traffic. ...
The United States Coast Guard (USCG) is a branch of the United States armed forces involved in maritime law enforcement, mariner assistance, search and rescue, and national defense. ...
This long range Radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to determine and map the location, direction, and/or speed...
A Vessel Traffic Service (VTS) is a marine traffic monitoring system established by harbor or port authorities, similar to air traffic control for aircraft. ...
Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). ...
LORAN (LOng RAnge Navigation) is a terrestrial navigation system using low frequency radio transmitters. ...
The Global Positioning System (GPS) is currently the only fully functional Global Navigation Satellite System (GNSS). ...
Cutaway of Anschütz gyrocompass The following description refers to the gyrocompasses used on ships. ...
The International Maritime Organization's (IMO) International Convention for the Safety of Life at Sea (SOLAS) requires AIS to be fitted aboard all ships greater than/equal to 300 gross tonnage for international voyages. It is estimated that more than 40,000 ships currently carry AIS class A equipment.[citation needed] Headquarters of the International Maritime Organisation in Lambeth, adjacent to the east end of Lambeth Bridge Headquarters building taken from the west side of the Thames Headquartered in London, U.K., the International Maritime Organization (IMO) promotes cooperation among governments and the shipping industry to improve maritime safety and to...
The International Convention for the Safety of Life at Sea (SOLAS) is the most important treaty protecting the safety of merchant ships. ...
Applications and limitations
Collision avoidance AIS is used in navigation primarily for collision avoidance. Due to the limitations of radio characteristics, and because not all vessels are equipped with AIS, the system is meant to be used primarily as a means of lookout and to determine risk of collision rather than as an automated collision avoidance system, in accordance with the International Regulations for Preventing Collisions at Sea (COLREGS). The International Regulations for Preventing Collisions at Sea 1972 (COLREGS) are published by the International Maritime Organization (IMO), and set out the rules of the road to be followed by ships and other vessels at sea. ...
 A vessel's text-only AIS display, listing nearby vessels' range, bearings, and names When a ship is navigating at sea, the movement and identity of other ships in the vicinity is critical for navigators to make decisions to avoid collision with other ships and dangers (shoal or rocks). Visual observation (unaided, binoculars, night vision), audio exchanges (whistle, horns, VHF radio), and radar or Automatic Radar Plotting Aid (ARPA) are historically used for this purpose. However, a lack of positive identification of the targets on the displays, and time delays and other limitation of radar for observing and calculating the action and response of ships around, especially on busy waters, sometimes prevent possible action in time to avoid collision. Image File history File linksMetadata Download high resolution version (1600x1002, 269 KB) Summary The picture shows a AIS display on board a vessel, listing vessels nearby with range, bearing and name. ...
Image File history File linksMetadata Download high resolution version (1600x1002, 269 KB) Summary The picture shows a AIS display on board a vessel, listing vessels nearby with range, bearing and name. ...
Night-vision is seeing in the dark. ...
This long range Radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to determine and map the location, direction, and/or speed...
Automatic Radar Plotting Aid, ARPA, gives a maritime radar the possibility to follow targets resembling other ships, calculating their course, speed and possible collision with own vessel. ...
While requirements of AIS are only to display a very basic text information, the data obtained can be integrated with a graphical electronic chart or a radar display, providing consolidated navigational information on a single display. ECDIS display (US Army) An Electronic Chart Display and Information System (ECDIS) is a computer-based navigation information system that complies with International Maritime Organization (IMO) regulations and can be used in lieu of paper navigation charts. ...
Vessel traffic services In busy waters and harbors, a local Vessel Traffic Service (VTS) may existing to manage ship traffic. Here, AIS provides additional traffic awareness and provides the service with information on what kind of other ships and their movement. A Vessel Traffic Service (VTS) is a marine traffic monitoring system established by harbor or port authorities, similar to air traffic control for aircraft. ...
Aids to navigation AIS was developed with the ability to broadcast positions and names of things other than vessels, namely it can serve to transmit navigation aid and marker positions. These aids can be located on shore, such as in a lighthouse, or on the water, on platforms or buoys. The US Coast Guard suggests that AIS might replace RACON, or radar beacons, currently used for electronic navigation aids.[1] A navigational aid or Navaid is any sort of marker which aids the traveler in navigation; the term is most commonly used to refer to nautical or aviation travel. ...
A HDR image of a traditional lighthouse For other uses, see Lighthouse (disambiguation). ...
A sea lion on navigational buoy #14 in San Diego Harbor Green can #11 near the mouth of the Saugatuck river. ...
Racon signal as seen on a radar screen. ...
The ability to broadcast navigation aid positions has also created the concept of Virtual AIS, also known as Synthetic AIS or Artificial AIS. The terms can mean two things; in the first case, an AIS transmission describes the position of physical marker but the signal itself originates from a transmitter located elsewhere. For example, an on-shore base station might broadcast the position of ten floating channel markers, each of which is too small to contain a transmitter itself. In the second case, it can mean AIS transmissions that indicate a marker which does exist, or a concern which is not visible (i.e. submerged rocks, or a wrecked ship). Although such virtual aids would only be visible to AIS equipped ships, the low cost of maintaining them could lead to their usage when physical markers are unavailable.
Search and rescue For coordinating resources on scene of marine search & rescue operation, it is important to know the position and navigation status of ships in the vicinity of the ship or person in distress. Here AIS can provide additional information and awareness of the resources for on scene operation, even though 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 position.
Binary messages The Saint Lawrence Seaway uses AIS binary messages (message type 8) to provide information about water levels, lock orders, and weather in its navigable system.[2] The Eisenhower Locks in Massena, NY. The St Lawrence Seaway is the common name for a system of canals that permits ocean-going vessels to travel from the Atlantic Ocean to the Great Lakes as far as Lake Superior. ...
Concern over web-based data In December 2004, the International Maritime Organization's (IMO) Maritime Safety Committee condemned the use of freely available AIS data published irresponsibly with the following statement.[3] Headquarters of the International Maritime Organisation in Lambeth, adjacent to the east end of Lambeth Bridge Headquarters building taken from the west side of the Thames Headquartered in London, U.K., the International Maritime Organization (IMO) promotes cooperation among governments and the shipping industry to improve maritime safety and to...
In relation to the issue of freely available automatic information system (AIS)-generated ship data on the world-wide web, the publication on the world-wide web or elsewhere of AIS data transmitted by ships could be detrimental to the safety and security of ships and port facilities and was undermining the efforts of the Organization and its Member States to enhance the safety of navigation and security in the international maritime transport sector.
How AIS works
Basic overview AIS transponders automatically broadcast information, such as their position, speed, and navigational status, at regular intervals via a VHF transmitter built into the transponder. The information originates from the ship's navigational sensors, typically its global navigation satellite system (GNSS) receiver and gyrocompass. Other information, such as the vessel name and VHF call sign, is programmed when installing the equipment and is also transmitted regularly. The signals are received by AIS transponders fitted on other ships or on land based systems, such as VTS systems. The received information can be displayed on a screen or chart plotter, showing the other vessels' positions in much the same manner as a radar display. Block quote Global Navigation Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. ...
Cutaway of Anschütz gyrocompass The following description refers to the gyrocompasses used on ships. ...
The AIS standard describes two major classes of AIS units: Class A - mandated for use on SOLAS Chapter V vessels (and others in some countries). Class B - a low power, lower cost derivative for leisure and non-SOLAS markets.
Other variants are under development specifically for base stations, aids to navigation and search and rescue, though they will all be derived from one of the existing standards and inter-operate with them.
Detailed description: Class A units Each AIS transponder consists of one VHF transmitter, two VHF TDMA receivers, one VHF Digital Selective Calling (DSC) receiver, and links to shipboard display and sensor systems via standard marine electronic communications (such as NMEA 0183, also known as IEC 61162). Position and timing information is typically derived from an integral or external global navigation satellite system (e.g. GPS) receiver, but may also use a LORAN receiver or an inertial navigation system. Other information broadcast by the AIS, if available, is electronically obtained from shipboard equipment through standard marine data connections. Heading information and course and speed over ground would normally be provided by all AIS-equipped ships. Other information, such as rate of turn, angle of heel, pitch and roll, and destination and ETA could also be provided. VHF radio is radio transmission in the 30-300 MHz frequency range, as a means of short-range, line-of-sight verbal communication. ...
This article or section does not adequately cite its references or sources. ...
Block quote Global Navigation Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. ...
Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ...
LORAN (LOng RAnge Navigation) is a terrestrial navigation system using low frequency radio transmitters that use the time interval between radio signals received from three or more stations to determine the position of a ship or aircraft. ...
An inertial navigation system measures the position and altitude of a vehicle by measuring the accelerations and rotations applied to the systems inertial frame. ...
The AIS transponder normally works in an autonomous and continuous mode, regardless of whether it is operating in the open seas or coastal or inland areas. Transmissions use 9600-bps Gaussian minimum shift keying (GMSK) modulation over 25 or 12.5 kHz channels using the High-level Data Link Control (HDLC) packet protocol. Although only one radio channel is necessary, each station transmits and receives over two radio channels to avoid interference problems, and to allow channels to be shifted without communications loss from other ships. The system provides for automatic contention resolution between itself and other stations, and communications integrity is maintained even in overload situations. BPS can stand for: The Bogomolnyi Prasad Sommerfield bound The British Psychological Society The British Pharmacological Society The Biophysical Society The additives BioPsychoSymmetrie therapy, an holistic oriented therapy Bits per second (more usually bps) Basis points one one-hundredth of a percentage point Business Planning and Simulation Battle Programmer...
Gaussian minimum shift keying or GMSK is a kind of continuous phase frequency-shift keying. ...
In telecommunications, modulation is the process of varying a periodic waveform, i. ...
It has been suggested that the section HDLC from the article Measuring_data_throughput be merged into this article or section. ...
In order to ensure that the VHF transmissions of different transponders do not occur at the same time the signals are time multiplexed using a technology called Self-Organized Time Division Multiple Access (SOTDMA). The design of this technology is patented, and whether this patent has been waived for use by SOLAS vessels is a matter of debate between the manufacturers of AIS systems and the patent holder. In order to make the most efficient use of the bandwidth available, vessels which are anchored or are moving slowly transmit less frequently than those that are moving faster or are maneuvering. The update rate of fast maneuvering vessels is similar to that of a conventional marine radar. The time reference is derived from the navigation system. HÃ¥kan Lans (born 1947) is an inventor from Sweden. ...
Each station determines its own transmission schedule (slot), based upon data link traffic history and knowledge of future actions by other stations. A position report from one AIS station fits into one of 2250 time slots established every 60 seconds on each frequency. AIS stations continuously synchronize themselves to each other, to avoid overlap of slot transmissions. Slot selection by an AIS station is randomized within a defined interval, and tagged with a random timeout of between 0 and 8 frames. When a station changes its slot assignment, it announces both the new location and the timeout for that location. In this way new stations, including those stations which suddenly come within radio range close to other vessels, will always be received by those vessels.
The required ship reporting capacity according to the IMO performance standard amounts to a minimum of 2000 time slots per minute, though the system provides 4500 time slots per minute. The SOTDMA broadcast mode allows the system to be overloaded by 400 to 500% through sharing of slots, and still provide nearly 100% throughput for ships closer than 8 to 10 NM to each other in a ship to ship mode. In the event of system overload, only targets further away will be subject to drop-out, in order to give preference to nearer targets that are a primary concern to ship operators. In practice, the capacity of the system is nearly unlimited, allowing for a great number of ships to be accommodated at the same time.
The system coverage range is similar to other VHF applications, essentially depending on the height of the antenna, but slightly better due to digital VHF and not analog VHF. Its propagation is better than that of radar, due to the longer wavelength, so it’s possible to “see” around bends and behind islands if the land masses are not too high. A typical value to be expected at sea is nominally 20 nautical miles (37 km). With the help of repeater stations, the coverage for both ship and VTS stations can be improved considerably.
The system is backwards compatible with digital selective calling systems, allowing shore-based GMDSS systems to inexpensively establish AIS operating channels and identify and track AIS-equipped vessels, and is intended to fully replace existing DSC-based transponder systems.
Shore-based AIS network systems are now being built up around the world. One of the biggest fully-operational, real time systems with full routing capability is in China, operated by China MSA and delivered by Saab TransponderTech in Sweden. The entire coastline is covered with approximately 150 base stations and 50 computer servers. Hundreds of shore based users, including ca 25 VTS centers, are then connected to the network and been able to see the maritime picture, but also to communicate with the ship with SRM:s (Safety Related Messages). All data is in real time and will full safety and security of ships and port facilities.
Broadcast information AIS transceiver sends the following data every 2 to 10 seconds depending on vessels speed while underway, and every 3 minutes while vessel is at anchor. This data includes: - Maritime Mobile Service Identity (MMSI) of vessel - vessel's unique identification
- Navigation status - "at anchor", "under way using engine(s)", "not under command", etc
- Rate of turn - right or left, 0 to 720 degrees per minute
- Speed over ground - 0.1 knot resolution from 0 to 102 knots
- Position accuracy
- Longitude - to 1/10000 minute and Latitude - to 1/10000 minute
- Course over ground - relative to true north to 0.1 degree
- True Heading - 0 to 359 degrees from eg. gyro compass
- Time stamp - UTC time accurate to nearest second when this data was generated
In addition, the following data is broadcast every 6 minutes: A Maritime Mobile Service Identity (MMSI) is a series of nine digits which are transmitted over the radio path in order to uniquely identify ship stations, ship earth stations, coast stations, coast earth stations, and group calls. ...
[[ Cutaway of Anschütz gyrocompass The following description refers to the gyrocompasses used on ships. ...
- IMO number - number remains unchanged upon transfer of the ship to other flag(s).
- Radio call sign - international radio call sign assigned to vessel
- Name - Name of vessel, max 20 characters
- Type of ship/cargo
- Dimensions of ship - to nearest meter
- Location of positioning system's (eg. GPS) antenna onboard the vessel
- Type of positioning system - such as GPS, DGPS or LORAN-C
- Draught of ship - 0.1 meter to 25.5 meters
- Destination - max 20 characters
- ETA (estimated time of arrival) at destination - UTC month/date hour:minute
Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ...
Differential Global Positioning System (DGPS) is an enhancement to Global Positioning System that uses a network of fixed ground based reference stations to broadcast the difference between the positions indicated by the satellite systems and the known fixed positions. ...
LORAN (LOng RAnge Navigation) is a terrestrial navigation system using low frequency radio transmitters. ...
See also HÃ¥kan Lans (born 1947) is an inventor from Sweden. ...
Automatic Packet Reporting System (APRS) is an amateur radio based automatic packet reporting system for tracking and digital communications, and was developed by Bob Bruninga, callsign WB4APR, at the United States Naval Academy. ...
Ham radio station with modern solid-state transceiver featuring LCD display and DSP capabilities Ham radio station with vintage vacuum tube gear featuring separate transmitter, receiver and power supply Amateur radio, often called Ham radio, is a hobby and public service enjoyed by about 6 million people throughout the world. ...
References and Footnotes - ^ US Coast Guard Navigation Center, Types of AIS
- ^ Great Lakes St. Lawrence Seaway System, AIS Project. Accessed December 15, 2006.
- ^ Maritime security - AIS ship data. 79th session: 1-10 December 2004. IMO Maritime Safety Committee. Retrieved on 2007-01-08.
- US Coast Guard's AIS Overview
- International Maritime Organization's AIS transponders information
December 15 is the 349th day of the year (350th in leap years) in the Gregorian calendar. ...
For the Manfred Mann album, see 2006 (album). ...
2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ...
January 8 is the 8th day of the year in the Gregorian calendar. ...
External links - AIS related
- Graphical AIS Tracking
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