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Chapter 11: Automatic Identification System (AIS) 167
Chapter 11: Automatic Identification System
(AIS)
11.1Introduction
This chapter details the AIS system and how it can be used as a safety aid. Once set up
you can overlay the AIS on chart or radar windows and use it to:
• Display a target (with heading/speed vectors and rate of turn) for any other AIS
equipped vessels.
• Display basic or detailed information for each target vessel including safety critical
target data.
• Set up a safe zone around your boat.
• View alarm and safety related messages.
11.2What is AIS?
AIS uses digital radio signals to broadcast ‘real-time’ information between vessels and
shore based stations via 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. AIS will augment your radar application, as it can operate in
radar blind spots and can detect smaller AIS fitted vessels.
WARNING:
Smaller vessels do not have to be fitted with AIS and whilst it is mandatory
for larger commercial vessels to carry AIS, its use is not. You should not
therefore assume that your AIS will display ALL vessels in your area. Due
prudence and judgement should be exercised.
AIS should be used to complement not substitute radar.
Classes of AIS data
AIS data is defined as Class A or Class B. The sending and receiving of Class A data is
compulsory for larger vessels. You will therefore be able to view all larger vessels on
your AIS display. Class B data is applicable to smaller vessels and is not compulsory.
You should not therefore assume that your AIS is displaying all smaller vessels in your
area.
Note: Not all AIS receivers will decode all information and not all of the Class A vessels
input all of the required AIS data. For example, some inexpensive AIS Class B receivers
do not decode and output the ship’s name, IMO number and vessel draft/beam/length,
destination etc.
81221_4.book Page 167 Tuesday, February 28, 2006 5:24 PM