Transcript Navigation - Chapter 2: Compass

Flotilla 12-10
Navigation Study Guide
Chapter 2: Compass
Instructor: Forrest Meiere
All Questions and Problems
from the Study Guide
PowerPoint Presentation
by Forrest Meiere
Flotilla 12-10
Navigation Study Guide
S2-1 In the modern compass, the north-seeking magnets
are attached to a ______________
lightweight dial or compass rose.
S2-2 The dials of most compasses are graduated in degrees,
cardinal points
with numbers every 30°, and the ______________
(N,E,S,&W). Arrows or other marks are sometimes used to
intercardinal points (NE,SE,SW, & NW).
denote the __________________
S2-3 The compass dial is supported on a jeweled bearing
which turns on a pivot. In turn, the pivot is mounted in a
gimbal system designed to keep the dial level with the
_____________,
horizon if the vessel pitches or rolls.
Flotilla 12-10
Navigation Study Guide
S2-4 Fastened to the gimbal is one or more
Lubber's Lines against which the dial graduations
can be read to determine the direction of the vessel
relative to the card.
S2-5 There are two principal types of compass dial
top-reading compass and the
design, the ___________________
front-reading compass
_____________________.
S2-6 During the mid-1920's an electronic compass
termed a fluxgate compass was developed for aircraft.
In recent years, this has become available to the
mariner.
Flotilla 12-10
Navigation Study Guide
S2-7 The modern magnetic compass is highly sensitive and
is able to align itself with weak magnetic fields , such as
the earth's magnetic field.
S2-8 However, the magnetic field aboard a vessel is not
solely due to the earth's magnetic field. Other shipboard
magnetic fields are caused by a variety of items, including:
shipboard electronics, windshield wiper, motors,
compressed gas horns, tachometers, electrical motors,
television sets and other equipment.
(no need to memorize this list; FM)
Flotilla 12-10
Navigation Study Guide
S2-9 These additional fields also affect the compass, with
the result that the compass heading of the vessel may differ
from its magnetic heading .
S2-10 Simply put, deviation is the difference between the
direction that the compass actually points and the direction
that it would point if there were no local magnetic fields
aboard the vessel.
S2-11 The mariner has two options for dealing with
ignore any residual error or correct for
deviation: _______
deviation.
Flotilla 12-10
Navigation Study Guide
S2-12 Unlike variation, which depends solely on the
vessel's position, deviation varies with the vessel's
heading
________.
S2-13 The process of developing a deviation curve is
swinging ship or swinging the compass
often termed __________________________________.
S2-14 If the compass bearing of an object is less than
the magnetic bearing, as determined from the chart, the
east A simple rule is
deviation is ____.
least, error east
“compass
_____________________.”
Flotilla 12-10
Navigation Study Guide
S2-15 A device for measuring relative bearings is termed
a pelorus .
S2-16 The letter sequence TVMDC is used to describe the
sequence of starting with a True course, correcting for
Variation to calculate a Magnetic course, and finally
__________
allowing for Deviation to calculate a Compass course.
S2-17 When converting from a true course to a compass
course (i.e. uncorrecting), westerly variation and deviation
are to be added .
Flotilla 12-10
Navigation Study Guide
S2-18 When converting from a compass to a true course
(correcting), East variation and deviation are to be added
and West variation and deviation are to be subtracted.
S2-19 It is important to remember that compass readings are
most accurate only when the vessel is level, traveling
at a constant speed , and maintaining a constant course.
S2-20 Otherwise a series of additional compass errors can
northerly turning error
arise, including _____________________
acceleration error; oscillation error; heeling error
____________________________________________.
(No need to memorize these errors. FM)
End of Questions
Flotilla 12-10
Navigation Study Guide
P2-1:
T
V
M
D
C
258M 29W 287C
P2-2:
T
V
M
060M
D
4E
C
056C
P2-3:
T
032
V
9W
M
D
041M 4W
C
045C
Flotilla 12-10
Navigation Study Guide
P2-4:
P2-5:
P2-6:
T
V
013 9W
T
V
M
022M
D
C
M
022M
D
4E
C
018C
T
V
M
D
C
013 9W 022M 4E 018C
270R
283 (True Bearing to Vessel)
Flotilla 12-10
Navigation Study Guide
P2-7 through P2-16: Variation = 015E
T
V
M
D
C
15E
P2-7
T
V
055 15E
M
040M
D
5E
C
035C
P2-8
T
V
149 15E
M
134M
D
1W
C
135C
P2-9
T
V
M
D
C
149 15E 134M 1W
135C
035R
184 (True) Bearing to Buoy
.
Flotilla 12-10
Navigation Study Guide
P2-10
P2-11
T
V
M
D
C
297 15E 282M 3W 285C
090R
387 (Subtract 360)
027 (True) Lighthouse Bearing
T
027
+180
207
T
207
V
M
D
C
15E
to find reciprocal
(True) Reciprocal Bearing
V
M
D
C
15E 192M Reciprocal
Flotilla 12-10
Navigation Study Guide
P2-12
T
V
M
D
C
196 15E 181M 4W 185C
285R
481 - 360 = 121: Bearing
+180 (to find reciprocal)
301 (True) Reciprocal
P2-13
T
V
110 15E
M
095M
D
3E
C
092C
285R
Buoy “6” Bearing 002C <== 362C
Flotilla 12-10
Navigation Study Guide
P2-14
T
V
200 15E
M
185M
D
C
4W 189C
P2-15
T
V
158 15E
M
143M
D
2W
C
145C
P2-16
T
V
338 15E
M
323M
D
0
C
323C
End of Problems