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A
A
1
B
B
1
A
1
A
B
B
1
Abbreviations and Data Terms
EXPLANATION OF DATA TERMS
BRG. Bearing is the direction, as measured in de-
grees from north in a clockwise direction. The re-
ceiver uses either true north or magnetic north, as
selected in the Setup Menu. The illustration shows
a simple compass rose with the eight cardinal direc-
tions noted with their bearing.
COG. Course over ground is the direction of movement expressed as bearing.
If a boat is pointing exactly north (0°) and there are no other factors affecting
its travel, the COG would be 0° but that is rarely the case. Water currents and
wind can affect the course the boat is taking.
If there is a current passing from left to right across the boat (90°) the COG
would change even though the bow of the boat is still pointing north. COG is
measured in degrees with North being 0°.
CTS. The optimum direction the vessel should be steered in order to effi-
ciently make headway back to the courseline while also proceeding toward
the destination waypoint. It is a "compromise" course bearng that projects
from your current position to a point on the courseline mid-way between a
point perpendicular to your position and the current leg destination waypoint.
DST. Distance to go to an active waypoint, or the distance between two
waypoints in a route leg.
ETA. Estimated time to arrival.
SOA. Understanding speed of advance is a little tricky but once you do it
becomes fairly simple. For this example we will use an exaggerated sample so
as to clearly describe SOA.
The boat is heading towards the buoy
and is currently at point A. If the boat
had followed its original course (A
1
–
buoy), it would be somewhere on the
line A
1
— B
1
. (The XTE for this sample
is the distance between points A and
A
1
.) In 1 hour he is at point B and
has travelled 34 NM (equivalent to a
speed of 34 knots).
Now if you project downwards to the course he should be on, you arrive at
point B
1
.
N
0°
E
90°
W
270°
S
180°
NW
315°
NE
45°
SW
225°
SE
135°