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Northstar M121/M84 Installation and Operation Manual110
Navigation data
BRG Bearing to Destination: Bearing to the destination from the boat.
BRG Bearing to cursor: Bearing to cursor from boat (cursor mode, see section 3-2-1)
CDI Course Deviation Indicator: When the boat is navigating to a point, the chart and highway windows
show a parallel line on either side of the plotted course. These two lines are called the Course Deviation
Indicator (CDI) lines. The distance from the plotted course to a CDI line is the CDI scale.
Set the CDI scale (see section 17-2) to the maximum distance that the boat should deviate from the
plotted course. The chart and highway windows show the CDI lines, which are like a highway over the
water where the boat will move. The windows show how far the boat has deviated from the plotted
course and if the boat is approaching a CDI line. If the XTE alarm is enabled (see section 17-8) an alarm
will sound if the boat reaches a CDI line.
COG Course Over Ground: Direction in which the boat is moving over the ground.
CTS Course To Steer: Optimum course to steer to return to the plotted course.
DTG Distance To Go: Distance from the boat to the destination.
ETA Expected Time of Arrival: At the destination, assuming that SOG and COG remain constant.
DST Distance from boat to cursor (cursor mode, see section 3-2)
SOG Speed Over Ground: Current boat speed over the ground. This is not necessarily the same as the boat
speed through the water nor the speed at which it is approaching the destination.
STR Steering: The diff erence between COG and CTS.
TTG Time To Go: The estimated time to reach the destination.
XTE Cross Track Error: The distance from the boat to the nearest point of the plotted course. XTE may have
a letter: R means steer to the right to return to the plotted course, L means steer to the left.
VMG Velocity Made Good: The speed at which the boat is approaching the destination.
CTS
SOG (speed)
VMG (speed)
BRG
COG
Destination
Boat position
Start
STR
DTG (distance)
CDI scale
(distance)
Plotted
course
Start
Destination
XTE
(distance)
Boat
position
CDI scale
(distance)
CDI line
Plotted
course
CDI line