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Appendix E
AIS overview
Your NAVIOM AIS uses digital radio signals to exchange 'real-time' information between vessels,
shore based stations, or aids to navigation (AToNs) on dedicated VHF frequencies. This information
is used to identify and track vessels in the surrounding area and to provide fast, automatic and
accurate collision avoidance data.
Although AIS augments your Radar app by operating in Radar blind spots and detecting smaller AIS-
fitted vessels, it does not replace your Radar, as it relies on receiving transmitted AIS information and
therefore cannot detect objects such as landmasses, navigational beacons or vessels not equipped
with AIS.
AIS limitation
Never assume that your AIS is detecting all vessels in the area. Always exercise due prudence and
do not use AIS as a substitute for sound navigational judgement.
Classes of AIS
Class A transceivers
Class A AIS transceivers transmit and receive AIS signals. AIS transceivers are currently mandatory
on all commercial vessels exceeding 300 tons that travel internationally (SOLAS vessels).
The following information can be transmitted by a Class A AIS system:
• Static data (Includes information such as MMSI number, vessel name, vessel type, call sign, IMO
number, length, beam and GNSS antenna location).
• Voyage related data (Includes information such as draft, cargo, destination, ETA and other
relevant information).
• Dynamic data (Includes information such as time (UTC), ship’s position, COG, SOG, heading, rate
of turn and navigational status).
• Dynamic reports (Ship’s speed and status).
• Messages (Alarms and safety messages).
Remember that not all vessels will transmit all of the information.
Class B transceivers
Class B AIS transceivers transmit and receive AIS signals, but use a reduced set of data compared to
Class A (see
Data Summary
). A Class B AIS transceiver can be fitted on any vessel not fitted with a
Class A transceiver, but is not mandatory aboard any vessel.
Data Summary
Data
Receiver (receive)
Transceiver
(transmit)
Transceiver
(receive)
Ship's name
Yes
Yes
Yes
Type
Yes
Yes
Yes
Call sign
Yes
Yes
Yes
IMO number
Yes
No
Yes
Length and
beam
Yes
Yes
Yes
Note:
NEVER assume that AIS is displaying information from all vessels in the area, because:
•
Not all vessels are fitted with AIS
•
Although it is mandatory for larger commercial vessels to carry AIS, it is not mandatory to use it.
AIS should be used only to augment Radar information, not substitute it.
Summary of Contents for AIS
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