20 Dead Reakoning
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Transcript of 20 Dead Reakoning
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Navigation
NAU 102
Lesson 20
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Dead Reckoning
From Deduced (ded.) Reckoning
Abbreviated DR
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Dead Reckoning
The process of determining present position by
projecting course and speed from a known
past position.
Definition
Or, the process of determining future position by
projecting course and speed from a known
present position.
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Dead Reckoning
Doesn¶t take into account any other factor.
Considers only course and speed.
Leeway (movement downwind)
CurrentSteering errors
Compass error
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Dead Reckoning
Determining course of advance
Speed of advance
EstimatedTime of Arrival
Uses
Voyage planning
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Dead Reckoning
Uses
Keeping track of location in th
e absenceof other positional information.
Out of piloting range.
Overcast sky.
GPS acting up.
Approximate location between fixes.
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Dead Reckoning
Determining outside forces.
Uses
If you know the forces, you can
compensate for them.
Wind
Current
Bad steering
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Dead Reckoning
Plan future movements after a fix
Uses
DR to determine course and/or speed
necessary to regain track or avoid a hazard
Compare position to desired location
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Dead Reckoning
DR Symbology
Use of standard symbols is important
Anyone else (Captain/Relief) caninstantly understand the situation.
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Dead Reckoning
GPS fix ± diamond
R-fix
DR position ± h
alf circle
Estimated position ± square
Running fix ± circle labeled ³R-fix
Visual fix ± circle
Electronic fix ± triangle
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Dead Reckoning
R-fix
TimesWritten horizontally for fixes and EP¶s
Written diagonally for DR¶s
1447
08121932
2000
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Dead Reckoning
Courses
Labeled ³C´
3 digits
True degrees unless otherwise markedWritten above the track line
Speeds
Labeled ³S´
Written below the track line
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Dead Reckoning
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Dead Reckoning
Rules of DR
4. After plotting a single line of position (LOP)
3. After every course or speed change
2. After every fix or running fix
1. At least every hour on the hour
Plot a DR:
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Dead Reckoning
Draw a line in the direction of the course
L
abel!
Using the mid-latitude, mark off the distance
Calculate the distance to next DR point
(using the Rules of DR)
(Use True directions only)
Constructing a DR
Start from a known position (a µfix¶)
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Dead Reckoning
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Dead Reckoning
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Dead Reckoning
Departure from Plan
Between fixes, you may fall off your planned
track.
From your latest fix, DR to regain track and/or
avoid navigation hazards.
Wind
Current
Bad steering
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Dead Reckoning
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Dead Reckoning
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Dead Reckoning
Fix Expansion
A DR is an approximation of position
based on very limited information.
There will always be inaccuracy and positional
error in every DR.
The longer the time since your last fix, the
greater the error.
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Dead Reckoning
Be extra vigilant when a navigational hazard
falls within your error circle.
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Dead Reckoning
Alternative format
for voyage planning.
Each turn point
(waypoint) is
labeled with ETA to
the point and
distance to
destination.
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I ntroduction to Navigation
Questions?