Piloting Course Chapter 3 Plotting & Planning Techniques United States Power Squadrons ®

Piloting Course Chapter 3

Plotting & Planning Techniques

United States Power Squadrons ®

Basic Plotting Techniques

Dead Reckoning• Determining position from prior fix

Bearings• Visually establish a position

2 Bearings establish a fix

• Related techniques Ranges Relative Bearings Seaman’s Eye

SKILL – Dead Reckoning

Maintain Position using

• Course &

• Distance Traveled

SKILL• Plot and Label DR Courses

Dead Reckoning

POSITION determined by:• Course Steered• Distance Traveled

DISTANCE determined by:• Direct-reading LOG• Speed x Time

60 Distance (nm) = Speed (knots) x Time (min)

or 60D = ST (called ‘60 D Street’)

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”

Slide 5

Dead Reckoning

Dead Reckoning Formula

Distance = S x T

(distance traveled)

(average actual speed)

(elapsed time)

60

T

S

Speed = 60 x D

Time = 60 x D

DR Accuracy

Helmsman Issues:• Accuracy of Course Steered

Cannot wander

• Accuracy of Speed Reading Difficult to obtain precise value

• Measurement of Time

Other factors:• Currents & Winds• Obstacles and other boats• Fatigue

DR Plotting & Labeling

DR Plot• Direction of Course Steered

DR Position• Nominally every hour

Calculate and Plot Distance traveled

• Plot at every Course or Speed Change

• Label Dot for location, surrounded by half-circle Time labeled on diagonal

Labeling DR Courses

C 070 M

S 6.01000

2. Label COURSE near starting point “C” (direction – 3 digits)

3. Label SPEED near starting point “S” (kn – 2 significant digits)

1. Draw & Measure COURSE LINE using course direction

4. Plot & Label DR Position dot – half circle Time (4 digits on diagonal)

1030

D = (S x T) / 60

D = (6.0 x 30) / 60

D = 3.0 nmFix

Exercise 3-1 – Plot & Label DR

Use Bowditch Bay Chart

Follow Instructions in Student Guide

Exercise 3-1How to maintain a DR plot. Using “Seaman’s Eye” to confirm DR positions.

At 0945, depart G “1” Fl G 2s Oyster River on a true course of 075º. Speed is 6.5kn.

At 1010, you change to a magnetic course of 355º.

At 1030, you increase speed to 8.5kn.

At 1105, you take up a true course of 090º.

What is a visual check on the 1030 DR position?

What is your sounding at the 1105DR position?

0945

T = 075V = 015WM = 090

C 090M

S 6.5

D = (ST)/60D = (6.5x25)/60D = 2.7nm

M = 355V = 015WT = 340 C

355M

S 6.5

1010

D = (ST)/60D = (6.5x20)/60D = 2.2nm

1030

C 355M

S 8.5

D = (ST)/60D = (8.5x35)/60D = 5.0nm

T = 090V = 015WM = 105

1105C 105M

S 8.5

SKILL – Bearings

Determine Position using

• Visual Bearings to Charted Objects

SKILL• Plot and Label Bearings

Bearings

Lines of Position (LOP)

• Based on direction of visible charted Landmarks

Direction from boat to landmark Plotted toward landmark Your location is somewhere on that line

– You cannot tell precisely where– You can estimate your position at the intersection

» DR Plot and LOP

• Taken on the Water Plotted & Labeled in real time Labeled

– Time of LOP on top of line– Bearing (Magnetic) below line

Sight Bearing from Boat to Landmark

Plot & Label Bearing

1030

070 M

Label Time abovethe line, andBearing belowthe line,

Methods – Taking Bearings

Hand-Bearing Compass

• Every boat should have one Handy Reasonably accurate Easy to use Good as backup compass

• Sight across ship’s compass Limited Inaccurate


Slide 17

Using Landmarks

Exercise 3-2 - Plot & Label Bearings

Use Bowditch Bay

Follow instructions in Student Guide

Exercise 3-2

Method for taking and plotting compass bearings. Plot and label the magnetic course, bearings & DR positions.

At 1005, depart R “8” I Q R Main Channel on a true course of 080º. Speed is 6.2kn.

At 1035, using a hand bearing compass, you take a bearing of 185º on R “6” Fl R4s Main Channel. Using “Seaman’s Eye”, how can you verify this bearing?

At 1110, you take a compass bearing of 355º on the Duttons Island light. What does this tell you about your speed?

1005C 095M

S 6.2

1035

T = 080V = 015WM = 095

D = (ST)/60D = (6.2x30)/60D = 3.1nm

MB = 185V = 015WTB = 170

1035

185M

D = (ST)/60D = (6.2x35)/60D = 3.6nm

MB = 355V = 015WTB = 340

1110

355M

1110

SKILL – 2-Bearing FIXes

Develop a FIX using

• Two Bearings

SKILL• Plot and Label Fixes

Fixes – 2 Bearings

FIX• Intersection of 2 or more Bearings

Accuracy• Determined by accuracy of each bearing• Depends on angle between bearing

Too close, poor accuracy (< 30°) (> 150°) 90° = ideal (2 bearings)

2-Bearing FIX

1030

070 M

1030

340 M

Exercise 3-3 - 2 Bearing FIX

Use Bowditch Bay chart

Follow Instructions in Student Guide

Using two bearings to plot a fix.

At 0900, depart RW “OR” Mo (A) Oyster River on a true course of 350º. Speed is 6.0kn.

At 0936, you take a compass bearing of 285º on Chapman Point light and a compass bearing of 355º on the light house north of Shark River. At the 0936 fix, take up a magnetic course of 077º. Increase speed to 11kn.

What are the L and Lo of the 0936 fix?

Observe the 0936 DR and fix positions. What happended?

Using “Seaman’s Eye”, what can you say about your 0936 fix?

Exercise 3-3

0900

C 005M

S 6.0T = 350

V = 015WM = 005

0936 285M

0936

355M

D = (ST)/60D = 6.0x36/60D = 3.6nm

CB = 285V = 015WTB = 270

CB = 355V = 015WTB = 340

09360936

M = 077V = 015WT = 062

C 077M

S 11

41º 41.4’N

72º 01.3’W

SKILL – 3-Bearing FIXes

Develop a FIX using

• Three or more Bearings

SKILL• Plot and Label 3-Bearing Fixes

3-Bearing FIX

3 Bearings • May not line-up• Potential for 3 intersections

Forms a triangle Position nominally at center of triangle

BREAK FOR THIS CHAPTER

Relative Bearings

Bearings using the Boat as reference

• Used occasionally

• Need obvious reference points on boat Bow Bearings Beam Bearings

• Falls into category of “Seaman’s Eye” Not precise, but good check

SKILL – Relative Bearings

Take Bearings relative to the Boat• Bow Bearing• Beam Bearing

SKILL• Plot and Label Relative Bearings

Bow Bearing

1030

070 M

070 M

Beam Bearing

1030

160 M

070 M

90R

Beam Bearing

1030

340 M

070 M

270 R

Exercise 3-4 - Relative Bearings



Using “Seaman’s Eye” to take bow and beam relative bearings.

At 1000, depart RW “OR’ Mo (A) on a true course of 349º. Speed is 6.0kn.

At 1019, you take a starboard beam bearing by “Seaman’s Eye” on R “10” Q R Main Channel.

At 1100, you briefly turn the bow toward Fl R 6s 40ft 10M HORN north of Shark River and take a bow bearing of 344ºM, and notice that the light on Chapman’s Point is exactly off your port beam. Plot the 1100 fix and steer a new course of 105ºM.

At 1147, you take a port beam bearing on the tower with a red light to the north.

Exercise 3-4

1000

C 004M

S 6.0

T = 349V = 015WM = 004

1019

094M

1100

344M

D = (ST)/60D = 6.0x19/60D = 1.9nm

RB = 090MH = 004MB = 094V = 015WTB = 079

1019

1100

D= (ST)/60D=(6.0x41)/60D= 4.1nm

1100

254M

RB = 000MH = 344MB = 344V = 015WTB = 329

1100

RB = 270MH = 344MB = 254V = 015WTB = 239

M = 105V = 015WT = 090

C 105M S 6.0

D = (ST) / 60D=(6.0x47)/60D = 4.7nm

1147

RB = 270MH = 105MB = 375V = 015WTB = 360

1147 015M

SKILL – Ranges

Pre-plotted Bearings using• Two visible charted landmarks or• Navigation aids

Provides a visual cue on the water to• Stay on Course• Find a specific location

SKILL• Use Ranges, Plot and Label your own

Ranges

Ranges

Ranges are Pre-Plotted Bearings• Use two visible charted landmarks• Bearing line intersects both

landmarks

Uses• Navigation in narrow channels• Alignment with Harbors• Formal navigation aids• Can build own to help navigate

Very Precise


Slide 39

Using a Range


Slide 40

Formal Range


Slide 41

Informal Range

Range Pictures

Exercise 3-5 - Ranges



Select and measure ranges from any two charted landmarks.

Create a range to the entrance of Perkins Cove, approaching it from the North on a magnetic course of approximately 200º. Assume that the tower on the west side of Perkins Cove is illuminated and its height to be 40ft.

Plot the range and create a turn into Perkins Cove

Exercise 3-5 – Ranges

T = 185V = 015WM = 200

Ran

ge

200M

T = 156V = 015WM = 171

C 171M

Seaman’s Eye

Informal Ranges

Bow & Beam Bearings

Other Reference Points on the Boat• Mark on rail

Using GPS to Navigate

Using GPS

• You get Precise Position – continuously

• But, how do you navigate and stay safe?

• Must periodically plot position on a chart

Essential to have reference to what is nearby Or, along your path Can be a tedious task

Better Approach: Pre-Planning

Create pre-qualified legs on the water

• Qualify them to be free of obstacles

Then, On-the-water – follow the paths

• Only need to refer to charts on occasion• Key – just stay on course

Pre-Planning

1. Make your plan

2. Follow your Plan

Characteristics of a Safe Path

1. Clear of Obstacles

2. Sufficient Depth for boat

Selecting a Safe Path

Step-by-Step

1)Draw ‘legs’ (paths)

2)Check for obstacles Shallow Water Rocks Wrecks Other Obstacles (poles, structures, etc.)

3)Safe Path Width Nominally about 1/10th nm on each side

– Equal to smallest increment on latitude scale– About 600 feet

Allows for helmsmanship, other boats, some drift


Slide 51

Minimum Path Width

Hazard Symbols

Redrawn from “How to Read a Nautical Chart”

Symbols for Obstructions

From: “How to Read a Nautical Chart”

What to look for…

Use Navigation Aids• Try to begin / end legs at navigation

aids Gives visible reference

Use visible landmarks• Provides a double-check reference

Take bearings as you go along

Depth• Sufficient clearance under the keel


Slide 55

Depth under the Boat

Working Around Obstacles

Build a Route Around Obstacles

• Create multiple legs


Slide 57

Planning on a Chart


Slide 58

Waypoint Terminology

Digital Charting - CD

Autoplay Menu

Simple Tools

A to B Measurements

Marking on Chart

Quick Route

Questions ? … Comments

Piloting Course Chapter 3 Plotting & Planning Techniques United States Power Squadrons ®

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Transcript of Piloting Course Chapter 3 Plotting & Planning Techniques United States Power Squadrons ®