Onwa Marine Electronics KS-200A - Manual (Page 5)

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How AIS Works
1. What is AIS
AIS stands for Automatic Identification System. AIS increases
navigational safety and collision avoidance by transmitting vessel
identification, helping to reduce the difficulty of identifying ships when
not in sight (e.g. at night, in radar blind arcs or shadows or at distance)
by broadcasting navigational intentions to other vessels by providing ID,
position, course, speed and other ship data with all other nearby ships and
land based stations.
According to IALA regulations, AIS is defined as follows:
AIS is a broadcast Transponder system, operating in the VHF maritime
mobile band. It is capable of sending ship information such as
identification, position course, speed and more, to other ships and to shore.
It can handle multiple reports at rapid update rates and uses Carrier Sense
Time Division Multiple Access (CSTDMA) technology to meet these high
broadcast rates and ensure reliable and robust ship to ship operation.
The IMO defines the performance standards as follows:
Ship to ship working, ship to shore working, including long range
application, automatic and continuous operation, provision of information
messaging via PC and utilization of maritime VHF channels.
2. What AIS classes do exist?
There are two classes of AIS units fitted to vessels, Class A and Class B.
In addition AIS base stations may be employed by the Coastguard, port
authorities and other authorized bodies. AIS units acting as Aids to
Navigation (A to N) can also be fitted to fixed and floating navigation
markers such as channel markers and buoys.
FOREWORD