Garmin GPSMAP 421/421s Owner's Manual - Page 49

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. 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. Heading and Projected Course of Activated AIS Targets When course over ground and heading 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 45). 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. Viewing Information 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-ofturn 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. Projected course Activated dangerous target MMSI Heading Direction of turn Target with Course over Ground, Heading, and Rate of Turn GPSMAP 400/500 Series Owner's Manual 43