This document provides an introduction to basic navigation concepts including: 1) Navigation enables locating one's position and traveling between places using tools like nautical charts, compasses, and coordinate systems of latitude and longitude. 2) Nautical charts depict water depths, hazards, and navigation aids to allow mariners to safely navigate coastal and ocean waters. 3) Key concepts in navigation include great circles, meridians, parallels, compass rose, cardinal and intercardinal directions, and units of measurement like nautical miles.

1. CHAPTER 1
INTRODUCTION TO NAVIGATION

2. Navigation enables mariners to:
• Locate their position
• Travel from one place to another

3. Terrestrial Sphere or Globe
A sphere on which is depicted a map
of the Earth (terrestrial globe)

4. North Pole
South Pole
The north and south poles are
located at the ends of the axis on
which Earth rotates.

5. North Pole
Meridians
South Pole
Lines running through the poles and
around the Earth are called meridians.

6. Equator
The great circle of the Earth that is
equidistant from the North Pole and
South Pole
(Cuts every meridian in half)

7. 60° 60°
30° Northern Hemisphere 30°
0°
EQUATOR 0°
30° 30°
Southern Hemisphere
60° 60°

8. Northern Western
Hemisphere Hemisphere
North Pole North Pole
South Pole South Pole
Southern Eastern
Hemisphere Hemisphere

9. Hemisphere
Half of a globe

10. N pole Greenwich
England
W E
LONGITUDE
EQUATOR
S pole
Meridians and the equator are called
great circles because they divide the
globe into two halves.

11. Great Circle
Any circle formed by the intersection
of a plane passing through the Earth’s
center, with the Earth’s surface

12. Prime
Meridian
Parallels
Equator
The equator is the only great circle
going around the globe from east to
west. The other lines are called parallels,
since they go around the globe parallel
to, and north and south of the equator.

13. Greenwich meridian
(longitude 0°)
N
Equator
(latitude 0°)
One example
of a great circle S
A great circle is any circle whose
plane passes through the Earth’s
center, no matter what direction.

14. What is the significance of the
great circle in navigation?

15. What is the significance of the
great circle in navigation?
The shortest distance between
two points on the Earth lies along
the path of a great circle passing
through those two points.

16. Arc
Any unbroken part of the
circumference of a circle or
other curved line

17. Circumference
The distance around a circular area

18. What is the circumference of the Equator?

19. 360° 360°
Greenwich meridian
N
Center of (longitude 0°)
The Earth Regardless of the
size of the circle,
the circumference
Equator
(latitude 0°) has 360°.
One example
of a great circle S

20. 360°
1° = 60 minutes
1 minute = 60 seconds

21. Measurement along a meridian
or parallel is expressed in terms
of degrees, minutes, and seconds
of arc (the curve of the circle).

22. Greenwich Royal
Observatory
0°
0°
The Greenwich meridian is numbered
0, or 0°, and is called the prime
meridian.

23. Prime Meridian
The meridian running through
Greenwich, England, from which
longitude east and west is measured

24. INTERNATIONAL DATE LINE
NORTH
POLE
PRIME MERIDIAN

25. International
Date Line
New Date
Noon
Old Date
Old Day 0° Prime
Meridian
New Day
Midnight 180°
International
Date Line
International Date Line

26. Eastern
Hemisphere
International
Date Line
Equator
Pacific
Ocean
Western Hemisphere

27. Prime
Meridian
0° Longitude
Meridians
Meridians (longitude lines) between the
prime meridian and 180th meridian are
numbered 0° to 180° east (E) or west (W).

28. Longitude
Measurement of position east or west
from the prime meridian

29. Greenwich
Prime
Meridian
W E
Longitude
The distance of arc east (E) or west (W)
of the prime meridian, measured along
a parallel

30. Longitude Lines

31. Latitude
Measurement of position north or
south of the equator

32. Latitude
The distance of arc north (N) or
south (S) of the equator, measured
along a meridian

33. Latitude Longitude
Equator
Prime
meridian
Grid system of latitude and longitude
lines

34. 90° 90°
EARTH’S
LATITUDE LONGITUDE
GRID

35. Remember!
North
Pole North
Latitude
South
Latitude
West East
Longitude South Longitude
Pole
• Longitude is always measured east
or west from 0° through 180°
• Latitude is always measured north
or south from 0° through 90°

36. New Orleans, LA
30N, 90W

37. Washington, D.C.
38°58'52"N
latitude
77°01'12"W
longitude
Express latitude
and longitude in
degrees, minutes,
and seconds.

38. Washington, D.C.
38°59'N latitude
77°01'W longitude
This is spoken
as thirty-eight
degrees,
fifty-nine
minutes north,
seventy-seven
degrees, one
minute west.

39. Washington, D.C.
38°58'52"N
latitude
77°01'12"W
longitude
Seconds are used
only if very exact
locations are
required.

40. Nautical Mile
One minute of arc measured along
the equator, or any other great
circle

41. 6,865 Nautical Miles
6,888
Nautical Miles
Equatorial Diameter - 6,888 Nautical Miles
Polar Diameter - 6,865 Nautical Miles

42. Comparison of a Statute Mile
to a Nautical Mile
STATUTE MILE = 5,280 FEET OR 1760 YARDS
NAUTICAL MILE = 6,076 FEET OR 2,000 YARDS
0 500 1000 1500 2000
YARDS

43. Dividers
Distance on a chart is measured along
the meridian, using a tool called dividers.

44. Measuring Distance

45. P
30 Nautical
Miles
60°
Parallel
52 Nautical
30° Miles
60 Nautical
Miles
0°
Length of a Degree of Longitude at
Various Latitudes

46. Remember!
Distances are not
measured on
parallels of latitude,
because one minute
equals one nautical
mile only along the
equator.
Dividers

47. 1 knot = 1 nautical mile per hour

48. Origin of the term knot
Chip Log
An old sailing day’s log for measuring
the speed of a vessel

49. True Nautical Direction
Measured from true north (North Pole)
as located on a globe

50. 32-point Compass

51. Cardinal Points
The four primary directions of the
compass; the north, south, east,
and west points

52. Cardinal Directions
North, South, East, West:
the four primary directions
of the compass

53. On the compass rose above, only north
is filled in. Fill in the rest of the points
on the compass, going clockwise, using
the standard abbreviations.

54. On the compass rose above, only north
is filled in. Fill in the rest of the points
on the compass, going clockwise, using
the standard abbreviations.

55. Express nautical directions in
three digits:
065° (Zero six five degrees)
090° (Zero nine zero degrees)

56. Heading – Direction the ship is facing
Course – Direction the ship is steered
through the water

57. MAGNETIC COMPASS GYROCOMPASS
Magnetic compasses Gyrocompasses
give direction relative reference true
to magnetic north. north.

58. Gyrocompass
Navigational compass containing a
gyroscope, that, when adjusted for
latitude and speed, shows true north
or communicates this information
to one or more gyro repeaters.

59. MAGNETIC TRUE
NORTH NORTH

60. Magnetic Compass
A compass having a magnetized
needle generally in line with the
magnetic poles of the Earth

61. NORTH
MAGNETIC
POLE
Canada
United States
Magnetic compasses point to the
Earth’s northernmost magnetic pole,
located in northern Canada.

62. Variation Angle
Difference between magnetic and true
north in degrees

63. How Variation Affects the Compass
Magnetic North North Pole
Variation
Remember, variation changes
depending on your position relative
to magnetic north.

64. Converting Direction
To convert from magnetic to true,
just add or subtract the variation
at your location to the magnetic
bearing.
Remember — Westerly variations
are subtracted, and easterly
variations are added.

65. Example of Converting Direction
If your ship was heading 080° magnetic
in a region where the variation was
10° East, what is the true heading?

66. Example of Converting Direction
If your ship was heading 080° magnetic
in a region where the variation was
10° East, the true heading would be
080° + 10°, or 090° true.

67. Example of Converting Direction
If your ship was heading 270° true in a
region where the variation was 10° East,
what is the magnetic heading?

68. Example of Converting Direction
If your ship was heading 270° true in a
region where the variation was 10° East,
the true heading would be 270° – 10°,
or 260° magnetic heading.

69. Bearing
The direction of an object from an
observer, measured clockwise in one
of three standard ways:
• True bearing
• Magnetic bearing
• Relative bearing

70. TN
Light
House
090°
TRUE
BEARING
True Bearing

71. True Bearing
Bearing using true north as the
reference

72. MAGNETIC TRUE NORTH
NORTH
Light
House
Difference between true and magnetic bearing

73. Magnetic Bearing
The direction of an object measured
clockwise from magnetic north

74. TN
RELATIVE
BEARING
030°
Light
House
Relative Bearing

75. Relative Bearing
The direction of an object measured
clockwise from the ship’s head (bow)

76. When recording a bearing, assume it to
be a true bearing unless followed by the
letters M or R.
030°M means 30° right of magnetic north
030°R means 30° off the starboard bow

77. Objects seen by lookouts are reported
in terms of relative bearing by degrees.

78. Relative Bearings
• Dead ahead, or bow – 000°R
• Starboard beam – 090°R
• Dead astern – 180°R
• Port beam – 270°R

79. To emphasize that it is a true bearing,
the letter T (for example 030°T) follows
the three-digit true bearing, spoken
―030 degrees true.‖

80. TN
RELATIVE
BEARING
030°
090°
TRUE Light
BEARING House
True Bearing = Relative Bearing + True Heading
(Subtract 360° if sum is greater than 360°)

81. Nautical Chart
Type of map used to navigate on
water

82. Nautical Chart
A nautical
chart is a
standardized
drawing
representing
part of the
navigable
waters of the
Earth.

83. Hydrography
Science of measurement, description,
and mapping of the Earth’s surface
waters, with special reference to their
use for navigation

84. Hydrographic information
given on a chart includes:
• Water depths
• Nature of bottom
• Overhead obstructions
• Navigation aids; buoys,
lights, and anchorages

85. Globe Chart
Impossible to Necessary to
work navigation work navigation
problems or problems
chart courses

86. Cartographers
Makers of maps and charts who use
math to work out chart projection
techniques

87. It is necessary
to convert the
round surface of
the globe to one
that is flat and
two-dimensional
(having only
length and
width)—to
a flat piece of
paper on which a
chart is drawn.

88. Planar Conical Cylindrical
Orthographic Perspective Conic Mercator
Chart projections

89. Chart Projection
Flat surface representative of the
Earth

90. Mercator Projection
The best-known map or chart projection

91. Mercator Projection
Earth is projected onto a
cylinder-shaped piece of paper,
wrapped around the globe at the
equator

92. Geradus Mercator
Mercator Projection
• Commonly used for navigational charts
• Developed by a Dutch cartographer,
Geradus Mercator, in the 1500s
• Most useful projection for navigation

93. Great Circle
Track
Rhumb Line
Conformal Projection
A projection on which any rhumb line is shown
as a straight line, used chiefly in navigation,
though the scale varies with latitude and aerial
size and the shape of large areas are greatly
distorted

94. Rhumb Line
A curve on the surface of a sphere
that cuts all meridians at the same
angle; the path taken by a vessel or
aircraft that maintains a constant
compass direction

95. Scale of Charts
SCALE 1:7,500,000
• Used to measure distance
• Relationship between actual
and chart distance
• Printed near the legend as
a ratio, such as 1:7,500,000

96. Small scales
are used to
depict large
areas on a
chart, and
large scales
are used to
depict small
areas.

97. Measuring distance on a chart
If an inch on the chart represents 50 miles,
what would five inches represent?

98. Measuring distance on a chart
If an inch on the chart represents 50 miles,
what would five inches represent?
250 Miles

99. Remember
• The larger the scale, the smaller the
area shown on a given chart or map.
• The large-scale charts show areas
in great detail.
• Features appearing on a large-scale
chart may not show up at all on a
small-scale chart of the same area.

100. Nautical Sailing
Types of Charts
Harbor

101. Nautical charts have information for
safe navigation, such as:
• Symbols, figures, and abbreviations
• Depth of water
• Type of bottom
• Navigational aids

102. Harbor charts are large-scale charts that
show harbors and their approaches in
detail.

103. Coastal
charts are
intermediate-
scale charts
used to
navigate a
vessel whose
position may
be determined
by landmarks
and lights,
buoys, or
soundings
offshore.

104. Sounding
The act of measuring the depth of an
area of water

105. General
ocean sailing
charts are
small-scale
charts
showing the
approaches
to large
areas of the
coast.

106. INTRODUCTION TO NAVIGATION
End of Part 1

107. INTRODUCTION TO NAVIGATION
Part 2

108. Depths of
water may
be given in
feet, fathoms,
or meters.

109. Fathom (of depth)
A unit of length equal to six feet
(1.8 meters); used chiefly in nautical
measurements

110. Plotting

111. Plotting
In order to use the nautical chart for
navigating, you must know something
about how courses, bearings, and
lines of position are plotted on it.

112. Parallel Rulers

113. Parallel Rulers
A pair of straightedges connected by
two pivoted crosspieces of equal
length so as to be parallel at all times;
used for various navigational
purposes, especially for transferring
the bearing of a plotted course to a
compass rose

114. Protractor
An instrument having a graduated arc
for plotting or measuring angles

115. Three-Arm Parallel Motion
Protractor Protractor (PMP)

116. Measuring
Distance on a
Mercator Chart

117. Fix (position)
Accurate position determined without
use of any previous position, using
visual, electronic, or celestial
observation

118. Line of Position
(LOP)
A line indicating
a series of possible
positions of a ship
as a result of
observation or
measurement

119. SPIRE
RANGE BEARING
Lines of Position
CAPE
DISTANCE ARC
TANGENT

120. Bearing Lines of Position
Lines corresponding to the bearings
are plotted on the chart. They are
labeled with the 4-digit time of
observation above the line.

121. Visual Range
Two landmarks or navigation aids are
observed in line, one behind the other

122. Rear
Marker
Front
Marker
Rear Marker Visual Range
Front Marker

123. A circular line of position
Distance Arc

124. Radar Stadimeter
Devices used to
measure distance
to a landmark
Sextant

125. Stadimeter
Optical distance-measuring device
that measures angles to determine
distance to an object using as a
reference the distance to an object of
known height

126. Stadimeter

127. Sextant
An astronomical instrument used to
determine latitude and longitude at
sea by measuring angular distances,
especially the altitudes of Sun, Moon,
and stars

128. Sextant

129. Obtain a fix with these combinations
of lines of position:
• Two or more lines of bearing
• A distance arc and a line of bearing
• Two or more distance arcs
• A visual range and a distance arc
• A visual range and a line of bearing
• Two simultaneous visual ranges
Most commonly used

130. TOWER
1545
A fix from two
crossed bearings

131. DOUBLE POINT
LIGHT
A fix by a
bearing and
distance from
the same object
1314

132. SMITH
POINT
HALL REEF LIGHT
A fix from three JONES
intersecting BLUFF
bearings

133. LIGHT
W
A fix from two
visual ranges
LIGHT
X
LIGHT
2152 W

134. Visual Fix
Electronic/Celestial Fix
Dead Reckoning Position
Estimated Position
Plotting Symbols

135. LIGHTHOUSE
1300 FIX
1245 FIX
TOWER
FACTORY
Marking Ship’s Fix

136. Piloting
The determination
of position by
visual means

137. Piloting
The determination of the course or
position of a ship or airplane by any
of various navigational methods or
devices

138. Navigation Aids
Compass
Bearing Circle
Fathometer
Chart
Stadimeter
Radar
Buoy
Lighthouse

139. Echo sounder (Fathometer)
Sonic device used to measure water
depth

140. Fathometer

141. Echo Sounder

142. Sound Ranging
A method for determining the distance
between a point and the position of a
sound source by measuring the time
lapse between the origin of the sound
and its arrival at the point
SONAR (S0und NAvigation
and Ranging)

143. In piloting, soundings are usually
taken every 5 minutes.
D=1/2 t x 4,800 feet per second

144. A fathometer may
establish a fix
when a navigator
has a chart
showing accurate
bottom contours,
but in practice it
usually serves as
a check.

145. Electronic navigation is
a form of piloting.

146. Electronic Navigation
Advantages
• Unaffected by weather
• Determines ship position electronically
Disadvantages
• Equipment malfunction
• Insufficient coverage

147. RADAR
RAdio Detection And Ranging

148. RADAR
Navigation system using reflected
pulses of energy

149. RADAR

150. Advantage of radar, as a navigational
aid, is that it does not require external
transmitting stations.

151. Disadvantage of radar, as a navigational
aid, is that maximum range is currently
limited to slightly more than line-of-sight.

152. Lighthouse
Use Reliable Radar Targets

153. Radar System

154. PIPS
Targets appear on the scope as
bright spots of light called pips.

155. The most common scope used is a plan
position indicator (PPI), which gives a
bird’s eye view of the radar coverage
area, the transmitting ship in the center.

156. Advantages of radar as a navigational
aid include:
• It can be used at night and during
periods of low visibility.
• A fix can be obtained from a
single object.

157. • Very accurate and rapid
• Used to locate and track storms
• Very important for ship safety

158. Loran
Long Range Navigation

159. Loran
Long range navigation system using
radio signals

160. Loran is a system
of radio signals
broadcast by
stations of known
position.

161. Loran Receiver
A loran fix is determined by a loran
receiver from the intersection of lines
of position obtained from those shore
stations.

162. GPS Satellites
Satellite Navigation
The newest electronic navigation system
is the Global Positioning System (GPS).

163. Global Positioning
System (GPS) • Six 10,900-
mile-high
orbits
• 24 satellites
• Continuous
three-
dimensional
fix capability
• Fix accurate
to within
±10 meters

164. GPS Navigation

165. GPS is used for a wide variety of land
navigation purposes, including position
and direction-finding in many new cars
and golf carts.

166. Military applications of GPS navigation
systems include guidance for:
• Smart bombs
• Cruise missiles

167. Differential GPS
Enhancement by to basic GPS: corrections to
positioning information is determined by land-
based receivers and transmitted to users.
Capable of accuracy to within + 1 meter.

168. Ship’s Inertial Navigation
System (SINS)
Provides accurate and continuous
dead reckoning (DR) positions

169. SINS gives ships an accurate and
continuous dead reckoning position
using three gyroscopes to determine
latitude, vertical, and longitude with
great accuracy.

170. Submarines use SINS to navigate when
submerged for months even when
traveling under the Arctic ice cap.

171. Celestial
Sphere
Celestial Navigation
Branch of navigation in which position is
determined by the aid of heavenly bodies
such as the Sun, Moon, and selected stars
and planets

172. The widespread availability of GPS is
fast making celestial navigation at sea
a vanishing art.

173. The sextant is used in celestial
navigation to measure the angle
(altitude) between a heavenly body
and the visible horizon.

174. Sextants

175. INDEX MIRROR
LENS
HORIZON
INDEX ARM HOOD
MIRROR
TELESCOPE
VERNIER
ARC SCALE
SCALE
MICROMETER
DRUM SCALE SCREW
Sextant — Nomenclature
Reading the Vernier Scale

176. Dead Reckoning
Calculation of one's position on the
basis of distance run on various
headings since the last precisely
observed position, with as accurate
allowance as possible being made for
wind, currents, compass errors

177. Visual Fix
Electronic/Celestial Fix
Dead Reckoning Position
Estimated Position
Plotting Symbols

178. FIX
DR POSITION
DESTINATION
1200
DEAD RECKONING TRACK

179. Set and Drift
Set – The direction in which a ship
is forced by wind and current
Drift – The speed of that force in
knots

180. FIX
DR POSITION
DESTINATION
1615
1600
1200
Effect of Set and Drift

181. A fix at 1200 is plotted and labeled.

182. A line is drawn from the fix on the
ship’s course of 073°. Course is
labeled above the line, and the
speed of 15 knots is labeled below
the line.

184. To find the 1300 DR position, use
dividers to measure 15 minutes of
latitude on the vertical latitude
scale printed on the side of the
chart.

186. The spot is labeled ―1300DR.‖

187. The Captain orders the Officer
of the Deck (OOD) to put ship on
a new course, 117° at 1330.

188. Using dividers, mark a spot 7½
miles from the 1300 DR position
along the direction the ship is
steaming.

190. Label position 1330DR, and
draw a new course line in the
direction of 117°.

192. Plotting a ship’s
DR track from one
fix to the next is a
1400 FIX continuous
process while
underway.

193. DR PLOT
1400 FIX

194. At sea, the navigator will use celestial or
electronic means to get positive fixes at
least every morning, noon, and evening.

195. In piloting waters, the navigator will
normally be on the bridge getting exact
fixes whenever usable navigation aids
come into sight.

196. Currently, electronic plotters incorporate
continuous fix updates received from
GPS, then project current ship’s position
and the DR track onto an electronic chart
projection on a computer screen.

197. Q.1. Define navigation.

198. Q.1. Define navigation.
A.1. The art and science by which
mariners find their ship's
position and guide it safely
from one point to another

199. Q.2. What is a chart?

200. Q.2. What is a chart?
A.2. A type of map used to navigate
on water

201. Q.3. What are the imaginary lines
that run through the poles and
around the Earth?

202. Q.3. What are the imaginary lines
that run through the poles and
around the Earth?
A.3. Meridians or lines of longitude

203. Q.4. What divides the Earth into the
northern and southern
hemispheres?

204. Q.4. What divides the Earth into the
northern and southern
hemispheres?
A.4. The Equator

205. Q.5. What is a Great Circle?

206. Q.5. What is a Great Circle?
A.5. Any circle drawn around the
Earth, the plane of which
divides the Earth into two equal
parts

207. Q.6. Are all meridians great circles?

208. Q.6. Are all meridians great circles?
A.6. Yes

209. Q.7. What is the name given to the
meridian on which the Royal
Observatory at Greenwich,
England, is located?

210. Q.7. What is the name given to the
meridian on which the Royal
Observatory at Greenwich,
England, is located?
A.7. The Prime Meridian

211. Q.8. Do parallel and latitudinal lines
run in the same direction?

212. Q.8. Do parallel and latitudinal lines
run in the same direction?
A.8. Yes

213. Q.9. Navigators determine their
ship's position using what
coordinate system?

214. Q.9. Navigators determine their
ship's position using what
coordinate system?
A.9. Latitude and Longitude

215. Q.10. If the latitude of the equator is
0 degrees, what is the latitude
of the North Pole?

216. Q.10. If the latitude of the equator is
0 degrees, what is the latitude
of the North Pole?
A.10. 90 degrees or north

217. Q.11. Latitude and longitude are
expressed in what units?

218. Q.11. Latitude and longitude are
expressed in what units?
A.11. Degrees, minutes, and
seconds

219. Q.12. How many degrees are there in
a circle?

220. Q.12. How many degrees are there in
a circle?
A.12. 360

221. Q.13. Approximately how many
yards are in a nautical mile?

222. Q.13. Approximately how many
yards are in a nautical mile?
A.13. 2000 yds.

223. Q.14. What are meridians?

224. Q.14. What are meridians?
A.14. Great Circles which pass
through the Earth’s poles

225. Q.15. In navigation what is a ―knot?‖

226. Q.15. In navigation what is a ―knot?‖
A.15. A seagoing term meaning one
nautical mile per hour

227. Q.16. How is direction expressed?

228. Q.16. How is direction expressed?
A.16. As an angle between 000
degrees and 359 degrees

229. Q.17. What are the cardinal points?

230. Q.17. What are the cardinal points?
A.17. North, East, South, and West

231. Q.18. Define ―true bearing.‖

232. Q.18. Define ―true bearing.‖
A.18. The direction of an object
measured clockwise from true
north

233. Q.19. What does chart projection
entail?

234. Q.19. What does chart projection
entail?
A.19. Projecting a three-dimensional
object on a two-dimensional
plane

235. Q.20. What is the best-known map or
chart projection called?

236. Q.20. What is the best-known map or
chart projection called?
A.20. Mercator projection

237. Q.21. What are the three basic types
of charts used by the Navy?

238. Q.21. What are the three basic types
of charts used by the Navy?
A.21. a. Navigational
b. Harbor
c. General ocean sailing charts

239. Q.22. What is a cartographer?

240. Q.22. What is a cartographer?
A.22. One who makes maps and
charts

241. Q.23. What is a fix?

242. Q.23. What is a fix?
A.23. An accurate position
determined without reference
to any previous position. The
intersection of 2 or more lines
of position.

243. Q.24. What is the difference between
directions measured on a
gyrocompass and those
measured on a magnetic
compass?

244. Q.24. What is the difference between
directions measured on a
gyrocompass and those
measured on a magnetic
compass?
A.24. Directions measured on a
gyrocompass are relative to
true north, whereas directions
measured on a magnetic
compass are relative to
magnetic north.

245. Q.25. How is distance on a Mercator
chart measured?

246. Q.25. How is distance on a Mercator
chart measured?
A.25. On a flat surface along any
meridian where one minute of
latitude equals one nautical
mile

247. Q.26. If a half-inch on a chart
represents 10 miles, how many
inches would represent 100
miles?

248. Q.26. If a half-inch on a chart
represents 10 miles, how many
inches would represent 100
miles?
A.26. Five inches

249. Q.27. What is the shortest distance
between two points on a
globe?

250. Q.27. What is the shortest distance
between two points on a
globe?
A.27. An arc of a great circle

251. Q.28. How many feet are in one
fathom?

252. Q.28. How many feet are in one
fathom?
A.28. Six feet

253. Q.29. What is a line of position
(LOP)?

254. Q.29. What is a line of position
(LOP)?
A.29. A line drawn on a chart along
which a ship must be located,
based on a bearing or distance
from an object or landmark

255. Q.30. A ship that is traveling south
observes another ship on a
relative bearing of 041 degrees.
What is the true bearing to that
ship?

256. Q.30. A ship that is traveling south
observes another ship on a
relative bearing of 041 degrees.
What is the true bearing to that
ship?
A.30. 221 degrees true
(180 degrees + 041 degrees)

257. Q.31. A ship that is traveling north
observes another ship on a
relative bearing of 041 degrees.
Where would you see that ship
in relation to your ship?

258. Q.31. A ship that is traveling north
observes another ship on a
relative bearing of 041 degrees.
Where would you see that ship
in relation to your ship?
A.31. Off the starboard bow

259. Sphere
A round body whose surface is at all
points equidistant from the center

260. Meridian
A great circle of the Earth passing
through the poles and any given
point on the Earth's surface

261. Parallel
Lines of latitude with only the equator
being a great circle

262. Dividers
A two–pointed compass used for
dividing lines and measuring

263. Compass Card
A circular card with magnets attached
to its underside, the face divided on its
rim into points of the compass, degrees
clockwise from north, or both, and
floating or suspended from a pivot so
as to rotate freely

264. Magnetic Compass
Directional instrument that points to
the north magnetic pole
Gyrocompass
Aligned with true north by means of a
spinning gyroscope

265. Distortion
The state of being misrepresented
a false

266. Development
of a Mercator
Projection

267. Sounding

268. LORAN CHART

269. Global Positioning System (GPS)
Electronic navigation system using
satellites