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GYROCOMPASS REPEATERS AND
PELORUS
Gyro repeaters mounted on the bridge wings are
located in stands somewhat similar to the binnacle.
These instruments display directional information on
the basis of electrical signals received from the ship's
master gyrocompass.
Gyro repeaters on the bridge wings are used in
taking bearings on objects outside the ship. Movable
sighting vanes on the face of the gyro repeaters are
aimed at the object in the same manner in which rifle
sights are lined up. True bearings are read directly by
observing the degree on the compass card with which
the crossbar of the sighting vane lines up. Relative
bearings may be read from an outer dumb compass ring
on the repeater stand.
True bearing is the direction of an object from the
observer, measured clockwise from true north.
Compass bearing is the direction of an object as
indicated by the magnetic compass. It must be
converted into true hearing by applying the corrections
for variation and deviation.
Relative bearing is the direction of an object from
the observer, measured clockwise from the ship's
heading as indicated by the lubber's line in the binnacle
Figure 2-5.— True and relative bearings.
or the gyro repeater. When a bearing is recorded, it is
assumed to be a true bearing unless it is followed by the
capital letter R, which would mean that the bearing is
relative. Figure 2-5 shows true and relative bearings of
a lighthouse from a ship.
As you learned in Basic Military Requirements,
lookouts report objects they see in relative bearings by
degrees (usually to the nearest 10 degrees) based on the
fore-and-aft line of the ship, starting with dead ahead as
000°, on the starboard beam as 090°, dead astern as
180°, on the port beam as 270°, and through to dead
ahead as 000°. Another look at the compass card in
figure 2-1 will show you the positions of the relative
bearings (in 10-degree increments) normally used by
lookouts.
Relative bearings by points of the compass are
sometimes used in certain problems connected with
fixing position in piloting. Each point of the compass is
equivalent to 011 1/4°, for a total of 32 points, as
opposed to the 36 relative reporting positions. Table 2-1
is included for familiarization purposes.
Without the need of your knowing exact
terminology, positions go on thusly around the ship in
the 1-2-3-4-3-2-1 pattern, punctuated by “dead astern”
and “on the port beam” to “dead ahead.” The relative
degree indications continue around the ship in 011 1/4°
steps, terminating at 000°.
Table 2-1— Relative Bearings by Points and Degrees
COMPASS POINTS
DEGREES
Dead Ahead
000
1 point on starboard bow
011 1/4
2 points on starboard bow
022 1/2
3 points on starboard bow
033 3/4
4 points (broad) on starboard bow
045
3 points forward of starboard beam
056 1/4
2 points forward of starboard beam
067 1/2
1 point forward of starboard beam
078
3/4
On the starboard beam
090
2-4
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