Document title: VMS-100 User Manual
Document number: VMSC-82
Company Confidential
©
2019 SRT Marine Systems plc
Page 6 of 21
2.
About this AIS 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 Navigation
Satellite System (GNSS) 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 transceivers, 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. They also transmit Class A transceivers are mandatory on
all vessels over 300 gross tonnes on international voyages and certain types of passenger
vessels under SOLAS regulations.
•Class B tran
sceivers. 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 statio
ns. AIS base stations are used by Vessel Traffic Systems to monitor and
control the transmissions of AIS transceivers.
•Aids to Navigation (AtoN) transceivers. AtoN’s 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, AtoN’s and AIS base stations but do not transmit any information about
the vessel on which they are installed.
This product 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.
Static data is information about the vessel which must be programmed into the AIS
transceiver. This includes:
•Maritime Mobile Service Identity (MMSI)
•Vessel name
•Vessel call sign (if available)
•Vessel type
