Automatic Identification System

Automatic Identification System

From Wikipedia, the free encyclopedia

The Automatic Identification System (AIS) is an automated tracking system used on ships and by Vessel Traffic Services (VTS) for identifying and locating vessels by electronically exchanging data with other nearby ships and VTS stations. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport.

A marine traffic coordinator using AIS and radar to manage vessel traffic.

An AIS-equipped system on board a ship presents the bearing and distance of nearby vessels in a radar-like display format.

A graphical display of AIS data on board a ship.

Information provided by AIS equipment, such as unique identification, position, course, and speed, can be displayed on a screen or an ECDIS. AIS is intended to assist a vessel's watchstanding officers and allow maritime authorities to track and monitor vessel movements. AIS integrates a standardized VHF transceiver with a positioning system such as a LORAN-C or GPS receiver, with other electronic navigation sensors, such as a gyrocompass or rate of turn indicator. Ships outside AIS radio range can be tracked with the Long Range Identification and Tracking (LRIT) system with less frequent transmission.

The International Maritime Organization's (IMO) International Convention for the Safety of Life at Sea (SOLAS) requires AIS to be fitted aboard international voyaging ships with gross tonnage (GT) of 300 or more tons, and all passenger ships regardless of size. It is estimated that more than 40,000 ships currently carry AIS class A equipment.[citation needed] In 2007, the new Class B AIS standard was introduced which enabled a new generation of low cost AIS transceivers. This has triggered multiple additional national mandates from Singapore, China, Turkey and North America affecting hundreds of thousands of vessels.

Contents [hide]

1 Applications and limitations

1.1 Collision avoidance

1.2 Vessel traffic services

1.3 Aids to navigation

1.4 Search and rescue

1.5 Accident Investigation

1.6 Binary messages

1.7 Computing and networking

1.8 AIS data on the Internet

1.9 Range limitations and space-based tracking

1.10 Type Testing and Approval

2 How AIS works

2.1 Basic overview

2.2 Message Types

2.3 Detailed description: Class A units

2.3.1 Broadcast information

2.4 Detailed description: Class B units

2.4.1 Message 14: Safety Related Message

2.4.2 Message 18: Standard Class B CS Position Report

2.4.3 Message 19: Extended Class B Equipment Position Report

2.4.4 Message 24: Class B CS Static Data Report

2.5 Detailed description: AIS Receivers

3 See also

4 References and footnotes

5 External links

[edit]Applications and limitations

[edit]Collision avoidance

AIS is used in navigation primarily for collision avoidance. Due to the limitations of VHF radio communications, 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).

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.

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.

[edit]Vessel traffic services

In busy waters and harbors, a local Vessel Traffic Ser