About your AIS class B transceiver
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2 About your AIS class B transceiver
2.1 About AIS
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 vessels. Position is derived from the Global Positioning System (GPS) and
communication between vessels is by Very High Frequency (VHF) digital transmissions.
There are a number of types of AIS device as follows:
• Class A transceivers. These are similar to class B transceiver, but are designed to be fitted
to large vessels such as cargo ships and large passenger vessels. Class A transceivers
transmit at a higher VHF signal power than class B transceivers and therefore can be
received by more distant vessels, and also transmits more frequently. Class A transceivers
are mandatory on all vessels over 300 gross tonnes on international voyages and certain
types of passenger vessels under the SOLAS mandate.
• Class B transceivers. Similar to class A transceivers in many ways, but are normally lower
cost due to the less stringent performance requirements. Class B transceivers transmit at a
lower power and at a lower reporting rate than class A transceivers.
• AIS base stations. AIS base stations are used by Vessel Traffic Systems to monitor and
control the transmissions of AIS transceivers.
• Aids to Navigation (AtoN) transceivers. AtoNs are transceivers mounted on buoys or
other hazards to shipping which transmit details of their location to the surrounding vessels.
• AIS receivers. AIS receivers will generally receive transmissions from class A transceivers,
class B transceivers, AtoNs and AIS base stations but do not transmit any information about
the vessel on which they are installed.
The em-trak B100 is an AIS class B transceiver.
2.2 Static and dynamic vessel data
There are two categories of information transmitted by an AIS transceiver: static and dynamic
data.
The vessel's dynamic data, which includes location, speed over ground (SOG) and course over
ground (COG), is calculated automatically using the internal GPS receiver.
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