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MT-550
9. AIS (AUTOMATIC IDENTIFICATION SYSTEM) RECEIVER
9.1 What is AIS
AIS (Automatic Identification System) is a collision avoidance aid system that
vessels exchange the navigation information like the MMSI number, position,
course, speed and destination etc with other vessels within VHF range.
Vessels of 300 tons and over making international voyages are mandated to be
fitted with AIS system, as well as cargo vessel of 500 tons and over not intended for
international voyages (It means that, smaller vessels do not have to be fitted with
AIS. You should not assume that you will receive the AIS data from all smaller
vessels in your area).
AIS broadcasts navigation information on two marine VHF channels. Frequencies
are 161.975MHz (AIS1) and 162.025MHz (AIS2).
Classes of AIS
There are two classes of AIS transponder, Class A and Class B. Information
transmitted by each class of AIS transponder is listed as below (You should
remember that not all vessels will transmit all of the information):
Data details
Class A
Class B
Static Information
Ship’s name
X X
Type
X X
Call sign
X
IMO number
X
Length and beam
X X
GPS antenna location
X X
Voyage Related Information
Draft
X
Cargo information
X X
Destination
X
ETA
X
Other relevant information
X X
Dynamic Information
Time
X X
Ship’s position
X X
COG
X X
SOG
X X
Gyro heading
X X
Rate of turn
X
Navigation status
X
Dynamic Reports
Ship’s speed
X X
Ship’s status
X X
Messages
Alarm
X X
Safety
X X
