Si-tex SAS-300, Руководство по эксплуатации

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Introduction
How AIS Works
The marine Automatic Identification System (AIS) is a location and vessel information reporting system.
It allows vessels equipped with AIS to automatically and dynamically share and regularly update their
position, speed, course and other information such as vessel identity with similarly equipped craft.
Position is derived from a Global Navigation Satellite System (GNSS) network and communication
between vessels is by Very High Frequency (VHF) digital transmissions. A sophisticated and automatic
method of time sharing the radio channel is used to ensure that even where a large number of vessels
are in one location, blocking of individual transmissions is minimised, any degradation of the expected
position reporting interval is indicated to the user and even if the unit suffers extreme channel overload
conditions it will always recover to normal operation.
AIS Class
There are two classes of AIS unit fitted to vessels, Class A and Class B. In addition AIS base stations
may be employed by the Coastguard, port authorities and other authorised bodies. AIS units acting as
aids to navigation (A to Ns) can also be fitted to fixed and floating navigation markers such as channel
markers and buoys.
Class A units are a mandatory fit under the safety of life at sea (SOLAS) convention to vessels above
300 gross tons or which carry more than 11 passengers in International waters. Many other
commercial vessels and some leisure craft also fit Class A units.
Class B units are currently not a mandatory fit but authorities in several parts of the world are
considering this. Class B units are designed for fitting in vessels which do not fall into the mandatory
Class A fit category.