Seiwa Marlin(v.16.31) - Manual (Page 5)

Addendum - 5
A.1 AIS
AIS is an Automatic Identification System. It has been introduced to improve the safety of navigation
by assisting in the efficient operation of ship-to ship, ship reporting and VTS applications. The system
should enable operators to obtain information from the ship automatically, requiring a minimum of
involvement of ship’s personnel, and should have a high level of availability. AIS transponders installed
on IMO vessels use VHF frequencies to:
• Transmit details of their own vessel
• Receive details from other vessels or navigation aids within VHF range.
Information being transmitted from vessels over 300 tons that, due to recent worldwide legislation, are
required to fit Class “A” AIS transponders.
Connecting to the chart plotter an AIS receiver (please contact your local dealer), vessels with AIS
transponder within VHF range are displayed on screen giving the skipper or navigator a visual
interpretation of the data of nearby vessels. This improves safety, and specifically for collision
avoidance reasons.
A.1.1 AIS System Definitions
• Target
It is a vessel equipped with AIS. Information about the Targets is being received by AIS Receiver and
displayed on the screen.
• CPA
Closest Point of Approach is the closest distance that will be achieved between your vessel and the
tracked Target, based on your vessel’s speed and direction and the Target’s speed and direction.
• CPA Limit
This is the distance from your vessel that a Target may reach before a Target is deemed a threat.
• CPA Alarm
Occurs if CPA is less or equal to CPA Limit. This test is done for active Targets only.
• TCPA
Time to closest Point of Approach is the time remaining until the CPA will occur.
• TCPA Limit
This is the time remaining before the CPA is reached.
• TCPA Alarm
Occurs if TCPA is less or equal to TCPA Limit. This test is done for active Targets only and if CPA value
is less or equal to CPA Limit.
• Radio Call Sign
International call sign assigned to vessel, often used on voice radio.
• Name
Name of ship, 20 characters.
• MMSI
Maritime Mobile Service Identity.
• MMSI number
A unique 9 digit number that is assigned to a DSC radio station. It primarily registers the boat information
in the U.S. Coast Guard’s national distress database for use in emergency situations.
• Active Target
Target located within the Activation Range. Active Target is represented by oriented triangle with COG
and Heading vectors. Rate of turn may also be displayed.
• Dangerous Target
Target detected by CPA or TCPA Alarm. Dangerous Target is Active Target by definition. For better
visibility Dangerous Target symbol is flashing.