Introduction to Automated Identification Systems (AIS)
Principally intended for collision avoidance, but as an adjunct rather than an automated collision avoidance system.
Complements collision avoidance of ARPA and VTS.
International Convention for the Safety of Life at Sea (SOLAS)
requires AIS to be fitted aboard
international voyaging ships of 300 or more gross tonnage, and all
passenger ships regardless of size.
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.
Self-organizing network principally using VHF radio interaction
between AIS on vessels or between vessel AIS & virtual AIS beacon
AIS transponders (transmit function)
- cooperatively broadcast information, such as their position,
speed, and navigational status, at regular intervals via a VHF
transmitter built into the transponder.
- Other information, such as the vessel name and VHF call sign, is
programmed when installing the equipment and is also transmitted
The signals are received by AIS transponders (receive function)
- fitted on other ships or on land based systems, such as VTS systems..
- 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
- Timing is vital to the proper synchronization and slot mapping for a Class A unit.
- Must have internal receiver (e.g., GPS) for time; can be used for location
- Usually gets location from external GPS, LORAN, etc. via NMEA 0183
- Other information broadcast by the AIS, if available, is
electronically obtained from shipboard equipment through standard
marine data connections.
AIS Installation Classes
Options for safety level and cost
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.GG
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.
AIS Synthetic Beacons
AIS Shore-based stations
Aids to navigation.
Normally reports every three minutes.
This may eventually replace radar beacons (RACON).
AIS can create a “synthetic beacon”
Radar beacons had to be physically on the hazard
AIS can simply add the position of a hazard to the broadcast
Wrecks, spills, etc. could be flagged in minutes