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8/8/2019 6 Projection, Distances
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Navigation
NAU 102
Lesson 6
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Lesson 6
Position, Distance & Direction
Where am I?
How far is it?
Which
way?
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Position
Shown relative to fixed object.
E.g. 1 nm north of
Chesapeake light
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Position
Shown by Lat/Long.
(e.g. 36 50.6N
075 31.2W)
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Position
Plotting Lat/Long.
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Position
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Position
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Position
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Loran
Hyperbolic system
Long Range Navigation
Based on time differences in received
signals from Master and Secondary
stations.
Results in hyperbolic lines of position
(LOPs)
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Loran
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Components
Master transmitting station
Two or more Secondary stations
Shipboard antenna and receiver
Loran charts
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Loran Chains
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Loran
Time Differences are displayed on a
shipboard receiver.
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Position Symbols
DR position half circle
R-fix
Visual fix circle
Electronic fix Triangle
Running fix circle labeled R-fix
Estimated position square
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Direction
Different ways to measure/state direction.
True direction angle from true north (T)
Magnetic direction angle from magnetic
north (M)
Relative direction angle from ships
heading (R)
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Direction
Direction is stated in degrees or points.
e.g. 045T vs. North East
e.g. 315R vs. 2 points to port
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Direction
Degrees
N = 000
Counted clockwise
from the reference
line.
E = 090
S = 180
W = 270
Stated in 3 digits
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Direction
32 points in a
circle
11.25 = 1 point
Points
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Direction
N = 0 pts = 000
Cardinal Points
E = 8 pts = 090S = 16 pts = 180
W = 24 pts = 270
Boxing the
Compass
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Direction
NE = 4 pts = 045
Intercardinal Points
SE = 12 pts = 135
SW = 20 pts = 225
NW = 28 pts = 315
Midway between
cardinal points
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Direction
NNE = 2 pts = 022.5
ENE = 6 pts = 067.5
ESE = 10 pts = 112.5
SSE = 14 pts = 157.5
Halfway between cardinal & intercardinal
NNW = 30 pts = 347.5
WNW = 26 pts = 292.5
WSW = 22 pts = 247.5
SSW = 18 pts = 202.5
Stated cardinal then intercardinal
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Direction
Remaining points
N by E = 1 pt = 011.25
Nearest cardinal or
intercardinal point by the
next cardinal point
NE by N = 3 pts = 033.75
NE by E = 5 pts = 056.25
E by N = 7 pts = 078.75
Etc., etc.
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Direction
Relative directions can be stated by
degrees or points.
e.g. 045 R or 4 points to stbd
e.g. 315 R or 4 points to port
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Direction
Bearing
Stated True, Magnetic or RelativeDirection of one object to another
e.g. stbd beam, fine on port bow, stbd
quarter, 2 points abaft the beam, etc.
Can be in Degrees, Points orWords
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Direction
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Direction
Bearing
To vs. From
A to B = 060T
A from B =240T
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Direction
You can convert between relative
and true bearings.
Relative Bearing + Ships Heading
= True Bearing
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Direction
R + S = T
R = T S
AndS = T - R
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Direction
Example
You are on course 170 T and you sight
a vessel abeam to starboard. What isthe true bearing of the vessel?
R +S
= T90 + 170 = 260 T
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Direction
Example
You are on course 250 T and on radar
you detect a vessel at 125 T. At whatis the relative bearing to the vessel?
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Direction
R = 125 - 250 = -125 R
-125 R ???
360 - 125 R = 235 R
You are on course 250 T and on radar you detect avessel at 125 T. At what is the relative bearing to the
vessel?
R = T - S
If < 0, add 360
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Distance
Measured using latitude scale on a
Mercator projection chart.
Use the scale at the mid-latitude of
what you are measuring.
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Distance
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Introduction to Navigation
Questions?