6 projection, distances

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?

6 projection, distances

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