Garmin GPSMAP 640 - Manual (Page 37)

GPSMAP 620 and GPSMAP 640 Owner’s Manual 31
Marine Mode: Managing Information From Other Vessels
Dangerous target in range. The target flashes while an alarm
sounds and a message banner appears. After the alarm is
acknowledged, a solid red triangle with a red line attached
to it indicates the location and the heading of the target. If
the AIS alarm is set to Off, the target flashes, but the audible
alarm does not sound and the alarm banner does not appear.
If the AIS transmission from the vessel is lost, a message
banner appears.
Dangerous target is lost. A red
X indicates that the AIS
transmission from the vessel is lost, and the chartplotter
displays a message banner asking whether the vessel should
continue to be tracked. If you discontinue vessel tracking, the
lost dangerous target symbol disappears from the chart or
the 3D chart view.
The location of this symbol indicates the closest point of
approach to a dangerous target, and the numbers near the
symbol indicate the time to the closest point of approach to
that target.
Heading and Projected Course of Activated AIS Targets
When heading and course-over-ground information are provided by
an activated AIS target, the heading of the target appears on a chart
as a solid line attached to the AIS target symbol. A heading line
does not appear on a 3D chart view.
The projected course of an activated AIS target appears as a dashed
line on a chart or a 3D chart view. The length of the projected
course line is based on the value of the projected heading setting
( page 33 ). If an activated AIS target is not transmitting speed
information, or if the vessel is not moving, a projected course line
does not appear. Changes in the speed, the course over ground, or
the rate-of-turn information transmitted by the vessel can impact
the calculation of the projected course line.
When course-over-ground, heading, and rate-of-turn information
are provided by an activated AIS target, the projected course of the
target is calculated based on the course-over-ground and the rate-
of-turn information. The direction in which the target is turning,
which is also based on the rate-of-turn information, is indicated by
the direction of the barb at the end of the heading line. The length
of the barb does not change.
Target with Projected Course, Heading
and Direction of Turn
Activated
AIS target
Projected course
Heading line
Barb