A bearing is a number which tells the direction of another ship or object.
A lookout gets bearings by sight, a conning officer by looking through the periscope, a sonar operator by listening through his gear. After contact is made
with a target, the sonar operator keeps reporting bearings continually. Therefore, he has to know what bearings are, and how to read and report them.
Usually a sonar operator reports
relative bearings because they tell
direction in relation to own ship.
Imagine two lines drawn from the
center of the submarine: the first
through the bow dead ahead, and
the second to the target. The angle
between these two lines, measured
clockwise from the first line, is the
relative bearing. A target dead
ahead is at 000 degrees relative. Since there
are 360 degrees in a circle, dead astern is
at 180 degrees relative. These three diagrams show relative bearings of
50 degrees, 160 degrees, and 240 degrees.
The sonar operator may also be ordered to report a target's true bearing.
Imagine two lines drawn from the center of the submarine: the first to the
North Pole, the second to the target. The angle between them, measured clockwise from the first line, is the true bearing. A target due North of the submarine
is at 000 degrees true, due East at 090 degrees true, due South at 180 degrees true, due West at 270 degrees
true no matter where the submarine is heading. Only when own ship is heading due North, will a target's relative bearing and its true bearing be the same.
Note how the true bearings are measured in the figures below.
Reading a bearing indicator
Below is a picture of a bearing indicator. It has three parts:
1. The outer scale represents relative bearings. Zero always points to your
own submarine's bow.
2. The inner scale represents true bearings. Zero always points to true
north, no matter where your submarine is heading.
3. The diamond-shaped bug has two tips which point out on both scales
the direction in which the projector is facing.
This is how to read the bearings
1. Read the relative bearing at the outer tip of the bug.
2. Read the true bearing at the inner tip of the bug.
NOTE: You can also read your own submarine's course on the
true (inner) scale by noting the degrees directly below zero relative.
When own ship changes course
The diagrams below show that the relative bearing changes when own
ship's heading changes. But the true bearing, measured from the motionless
North Pole, is fixed. Therefore keeping the true bearing in mind helps the
operator maintain contact with a target, no matter where his submarine is
Know these general terms
The direction of a target
may also be described in
a more general way, as
shown in the diagram at
the right. Ahead, astern...
port and starboard...bow,
beam, and quarter...these
are familiar words. But you
must learn to know these
eight combinations by
heart, so that the instant
you hear any one of them,
you get a picture of the
general direction of the
target in relation to your