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1. Outline of AIS
Automatic Identification System is a high-tech device which is showing real time voyage
information as such position, route, speed of ships. It is a device to prevent from doing
collision of ships on sea as well as comply with IMO regulation. It is possible to identify
position of other ships, judge the voyage routes even if status of not viewing any targets by
radar and to manage more efficient secure activities as such preventing against collision,
wide-range monitoring, search and rescue.
Automatic Identification System is operated at a bandwidth of VHF frequency and ITU
(International Telecommunication Union) a WRC (World Radio communication Conferences)
in 1997 has designated 161.975 MHz (87B channel), 162.025 MHz (88B channel) as two VHF
frequencies for AIS.
2. Technical outline of AIS
It is communicated by simplex, semi-duplex, duplex using TDMA (Time Division Multiple
Access) protocol and the bandwidth is less than 25kHz. It consists of A Class transceiver and
B Class transceiver and it is equipped to ships in accordance with the purpose.
A Class Transceiver: Installed mandatory to international passenger ships and
international ships (less than 300 tonnage) and make a report
for position on the voyage.
B Class Transceiver: Installed to ships of less than 65 feet-height and it is not
mandatory regulation.
The four information report of AIS are as followings.
Static Information: IMO number, MMSI, Call sign/Name, Length/Width, Type,
position of on-ship location (locations of forward, backward, leftward, rightward of
ship) are reported per 6 minutes or those are reported whenever data is changed or
called.
Dynamic Information: It contains accurate command and ship’s position in
perfect condition, UTC, Course Over Ground (COG), Speed Of Ground (SOG), Heading,
Voyage Status, Ratio of Turn. Those are shown in accordance with speed and heading
turn as a following table.
