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Magellan NAV 600092
A
Courseline
B
C
D
E
STR. Steering. The difference between COG and CTS. If COG is
25° and CTS is 30°, then STR is 5° Right.
TTG. Estimated time en route to reach the active waypoint.
TRN. Turning is the difference between COG and BRG. If COG is
80° and BRG is 75°, TRN is 5° left.
VMG. Velocity made good is the component of the velocity that is in
the direction of the destination. In the above example, the boat is
travelling directly towards the destination even though not on the
courseline originally set. In this case, all of this velocity is being ap-
plied towards arriving at the destination, (i.e., VMG = SOG). Should
the boat veer away from this course and travel in a line parallel to the
original courseline (A
1
;B
1
) it would be travelling on a course that would
not intercept the destination waypoint. As the boat moved along, less
and less of its velocity would be applied toward arriving at the destina-
tion. By the time point D is reached, none of the velocity is applied to
getting closer to the destination and the VMG would be 0. As it moves
to point E, it is moving away from the destination and its VMG is a
negative value.
XTE. XTE (cross track er-
ror) is the perpendicular
distance from your boat to
the left or right of the
courseline that you are trav-
elling. As you will see in the
discussion of other data
items, XTE is important in
computing them accurately.
Keeping XTE at a mini-
mum will help maintain the
most direct route to your
destination. This illustra-
tion shows a boat courseline. The arrows between the boat and the
courseline is the distance of XTE and this boat is to the left of the
courseline. This boater would need to steer right to close the XTE.