On the bottom, a typical
Both vessels in the above illustration are equipped with an AIS transceiver. Due to “Time – Synchronization”, they use the same organization of free and allocated windows (slots) in the shared VHF Data Link (this method is called “Carrier Sense Time Division Multiple Access”) to send and receive messages. Without the necessity of any operator interaction, both vessels know exactly who or what is cruising nearby and where the individual object is heading.
The scenario below shows a full AIS coverage area (including all applications and complete shore infrastructure).
2.AIS classes
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 Coast Guard, 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.
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 may be fitted with Class A units.
Class B units are designed for fitting in vessels which do not fall into the mandatory Class A fit category. The
ACR
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