AIS-CTRX Class B AIS Transponder Manual
INFORMATION ABOUT AIS
General
AIS (Automatic Identification System) is the name of a system that makes it possible for ships to
identify other ships and to monitor ship movements. The reason for implementing the AIS system is for
the mariner to obtain more information about ships in the vicinity than what radar is able to provide.
AIS gives e.g. information about a ships identity (name, call sign, IMO number and MMSI), size this
even for ships behind Island or bends that radar cannot detect.
AIS is used to enhance safety for life at sea, improve safety and efficiency in navigation and protect
the marine environment.
AIS-information transmitted from a ship contains of three (3) different main types:
- Static data that was programmed into the AIS equipment at installation and it only needs to be
changed if the ship changes its name, flag or undergoes a major refit where size or ship type is
changed;
- Dynamic data contains information that automatically is updated from ship sensors like the heading
from the Gyro, Position and speed from GNSS equipment. Also navigational status belongs to the
group of dynamic data but is updated manually by the crew; and
- Voyage related data that manually is updated by the crew along the voyage.
From the start AIS some times also was referred to as UAIS or as the 4S transponder system that
meant Ship to Ship and Ship to Shore.
IMO adopted 1998 a performance standard for AIS within the SOLAS requirement that described in
general how AIS should work. Below follows a brief description of the main requirements for AIS from
the performance standard:
•
Automatically provide information to AIS land stations, other ships and airborne units e.g. SAR
helicopters about the ships identity, Type of ship, Position, Course, Speed, Navigational status
(e.g. under way using engine, at anchor) and other safety related information of importance.
•
Be able to receive the same type of information from other ships.
•
Be able to monitor and track other ships.
•
Exchange information with land based AIS systems.
AIS is an automatic system that continuously and simultaneously transmits on two channels in the
maritime VHF frequency band.
AIS can handle several reports in a rapid consecutive flow. To accomplish these AIS uses a technique
called Self Organized Time Division Multiple Access (SOTDMA) that guarantees high transmission
safety and operational robustness.
AIS also allows for other types of information from e.g. sensors like Gyro, GPS and echo sounders etc.
to be transmitted automatically.
Important areas where AIS is used are:
•
Information exchange between ships within VHF range (normally 20-30 NM) to enhance
safety at sea and to improve situation awareness.
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