Chapter 1: Introduction
Introduction to AIS 3
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Introduction
If a vessel operating in a mandatory ship reporting system does switch off
its AIS, this should be reported to the relevant authority. Note that some
data is entered or updated manually, meaning that there is potential for
false entry and for the entered data to become out of date. This includes
data related to static information (e.g. ship identity, dimension) and voyage
related data (e.g. navigational status).
AIS and radar
A difference between AIS and radar is that AIS uses an absolute referencing
system to determine the position, whereas radar determines the position by
relative measurements from the vessel or shore base to observed targets.
AIS may be used together with radar information to provide:
• Vessel identification, heading, course over ground (COG) and speed over
ground (SOG)
• Improved vessel tracking (no target swap)
• Wider geographical coverage
• Greater positional accuracy, dependent on the position input sensor
• Information in radar shadow area ('sees' around bends and behind
islands)
• Maneuver data in nearly real time
• No loss of targets in sea, rain and snow clutter
AIS classes
AIS is not only used on board ships. It can be grouped by 'class' (shipborne)
and function. A Ship borne AIS device which contributes by most of the
flow of AIS information, is classified as either Class A, B or Inland AIS. The
AIS Class A stations are ship borne units which meet IMO performance
standards and are required on most commercial ships by the International
Maritime organization (IMO). The SAILOR 6282 AIS Transponder is a a
combined Class A and Inland AIS station.
Note
Not all ships are required to have AIS. Furthermore, AIS may be
switched off if there is a potential risk that the operation of AIS
might compromise the safety or security of the ship, or if security
incidents are imminent.
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