Section 5 - Piloting - Plotting a Course

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• Welcome to the
• United States Power Squadrons'
• Chart Smart Seminar

Piloting - Determining Position (Section 7)
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Class Agenda - cont'd

• Section 7 Piloting - Determining Position
• Dead Reckoning
• Class Plotting Exercises

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Definitions

• Dead Reckoning (DR)
• Calculating a boat's position based on its
  course, speed, and time run from a previous
  position
• Dead Reckoning (DR) Track
• The intended course line of a vessel as plotted
  on a chart
• DR Position
• The presumed position of a vessel on a DR track

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Rules for Plotting DR Tracks

• Must start from a known position

• Can only restart from known position

• Use only true courses for labeling

• Use only speed through the water

• Calculate and plot DR position hourly

• Plot DR position at time of every change
• of course and speed

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Labeling a DR Track and Position
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Bearings

• Magnetic Bearing
• Bearing taken using the compass
• True Bearing
• Magnetic bearing corrected for
• local variation East or West
• Can be plotted on a chart as a line
• of position

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Compass to True Bearing
Deviation is assumed to be 0 for
demonstration only
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A Bow-On Bearing

North
True Bearing "To"
TB 040

Variation
V 15
W
Magnetic Bearing
MB 055

Deviation

D 0
W
Compass Bearing "To"
CB 055
Compass Direction - 055?
Determining a Line of Position - as a graphical
aid, plot the reciprocal true bearing (040 180
220) from the navigation object
Note deviation is assumed to be zero for
demonstration only
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A Bow-On Bearing
North
Compass Direction - 055?
Determining a Line of Position - as a graphical
aid, plot the reciprocal true bearing (032 180
212) from the navigation object
Note deviation determined from example
Deviation Table displayed in Class 1
interpolated to 055
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Fix By Two Bearings
Note 1430 fix time label is to be parallel to
the bottom of the chart 1430 DR time label is
to be at an angle to the DR track.
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Mark at 303
Note 1430 fix time label is to be parallel to
the bottom of the chart 1430 DR time label is
to be at an angle to the DR track.
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Mark at 303
Note 1430 fix time label is to be parallel to
the bottom of the chart 1430 DR time label is
to be at an angle to the DR track.
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Class Exercise 5
Use the Sample Plotting Sheet (Figure 23 in your
text) to work through the problems starting on
page 44 and continuing on page 45.
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Class Exercise 6 - Chart Work
Positioning by Compass Bearingson the
Bowditch Bay Practice Chart
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Bowditch Bay Chart Work Problem 6
You are enroute from RG "D" Gong to R "6" and
take bowon compass bearings at 1320 on (1)
Fl 8 sec 42ft Lt Ho on Duttons Is - 087
(2) Fl 8 sec 20ft Lt Ho on Channel Is -
267 (3) Fl Red 4 sec R "6" - 196 Correct
the compass bearings to true bearings (assume
deviation is zero) Plot and label your bearings
fix on the chart and determine latitude and
longitude.
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Compass to True Bearing
Duttons Is
Channel Is
R "6"
T 072 T 252 T
181 V 15 W V 15 W V 15
W M 087 M 267
M 196 D 0
D 0 D 0 C 087
C 267 C 196
Add East Subtract West
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1320 072
1320
1320 252
1320 181
FIX
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Position of Fix
Latitude 41 43.1 ' N Longitude 071 19.7
' W
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End of Section 7
Piloting - Determining Position
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Questions ? Comments ?
End of Seminar