Seiwa Starfish 2nd Edition - Manual (Page 51)

53 User Manual
Position Filter : Selects Low/Medium/High/Off the Position Filter. In case of a jittering fix this option makes the
ship's position more stable and the track smoother.
Speed Filter : Selects Low/Medium/High/Off the Speed Filter. When it is On, you can filter the speed of the ship,
to optimize it.
Bearing : Selects either degrees magnetic, Auto Mag, or True. If magnetic readings are selected the
variation is computed automatically for every zone as soon as the chart is displayed.
Magnetic Variation : It is possible to calculate the Magnetic Variation in an Automatic or manual mode, by inserting
the step for calculation of Magnetic Variation.
Calibrate Compass : The variation table is used to match magnetic value readout on the chart plotter comparable
with the value given by the compass of the boat. In other words, since the compass of the boat
must be compensated (due to the iron masses, ...), we use the same values given by the chart
plotter. This means that, for example, if the BRG to the next Waypoint readout in the chart
plotter display is "X" Mag degree, if you steer the boat reading "X" Mag degree from the
compass, you are driving well toward the next Waypoint.
3.8 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.
3.8.1 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 be-
tween 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.