Boating Skills & Seamanship

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# Boating Skills & Seamanship - PowerPoint PPT Presentation

Boating Skills & Seamanship. Lesson 9 Introduction to Navigation. Lesson Objectives. Select, Use, And Keep Current Charts Identify Objects On A Chart Use Piloting Tools Compass Mounting Determining Position (LOP) Measuring Distance On Charts Principles Of Dead Reckoning

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## Boating Skills & Seamanship

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### Boating Skills & Seamanship

Lesson 9

Approved by DC-E USCG AuxA, Inc

Lesson Objectives
• Select, Use, And Keep Current Charts
• Identify Objects On A Chart
• Use Piloting Tools
• Compass Mounting
• Determining Position (LOP)
• Measuring Distance On Charts
• Compute Time,Speed, And Distance
Navigator’s Tools
• Charts
• Magnetic Compass
• Course Plotter – Parallel Rulers
• Dividers
• Good Pencils - Erasers
• Binoculars - 7 x 50
• Means Of Finding Water Depth
• Electronic Tools
Map vs Chart
• Map
• Symbolic picture of a position of the earth drawn to scale
• Nautical Chart
• Map that emphasizes features useful to the mariner
• Shape of the coastline
• Landmarks
• Depths
Chart Projection
• Converts Spherical Area (Earth) To A Flat Piece Of Paper (Chart)
• Two Main Types Of Projections
• Mercator
• Conical
The Mercator Projection
• Points On The Earth Projected Onto Cylinder
• Portions Of Cylinder Become Flat Surface When Cut Apart
• All Angles Correctly Represented So Course Lines Can Be Measured Accurately
• Distortion Magnified As You Go North Or South, So Unusable Near Poles

A

A Mercator Projection

Lines of Longitude Projected Parallel

The Further AwayFrom The Equator,

The Greater The

Distortion

Spherical Surface Projected On A

Cylinder

The Polyconic Projection
• Earth’s Surface Projected On A Series Of Cones
• Less Distortion At High Northern And Southern Latitudes
• Measuring Can Only Be Done From The Center Of The Chart
Conical Projection

Less Distortion in Northern/Southern Areas

Strip Charts
• Segments Of Larger Traditional Charts
• Printed On Small Panels & Enclosed In A Folder
• Easier To Handle On Small Boat
• Sections May Not Be Printed With North At The Top
Chart Scales
• Large Scale = Small Area
• Small Scale = Large Area
• 1:80,000 Smaller Scale Than 1:40,000
• 1:80,000 Means 1 INCH On CHART Equals 80,000 Inches On Earth
• Always Use Largest Scale Possible
Harbor 1:2,000

1:40,000

Coast 1:40,000

1:150,000

General 1:150,00

1:600,000

Sailing 1:600,000

1:14,000,000

Chart Scales (Cont)
Chart Datum
• Datum
• Benchmark term from which a chart’s vertical or horizontal measurements are made
• Vertical Clearance
• Based on Mean High Water
• Depth
• Based on Mean Lower Low Water (MLLW)

Vertical Clearance

Actual Clearance

MHW

Mean Range

Height of Tide

MLW orMLLW

WaterDepth

Charted Depth

Vertical Chart Datum

Boat’s Actual Clearance

Positions On The Surface Of The Earth
• System Of Coordinates
• Great Circle - a plane that passes through the center of the earth
• When it also passes through both Geographic poles it is a Meridian or Line of Longitude
• The Equator is also a Great Circle
• Small Circle – any plane passing through the earth but not the CENTER of the earth.
• a small circle plane that is parallel to the equator is called a Parallel or Line of Latitude
Latitude and Longitude

Parallels of Latitude

Meridians of Longitude

Measuring Latitude

Line A-B

Center of the earth to equator (radius)

Line A – C

Center of earth to parallel

Angle = 60 º

C

A

B

Measuring Direction
• Use Chart’s
• Compass Rose (360° in any direction)
• Meridians of Longitude (vertical coordinate)
• Parallels of Latitude (horizontal coordinate)
• Tools
• Compass
• Parallel Rulers
• Course Plotter
• Paraglide Plotter
• Dividers

Inclinometer

Direct Digital

Telltale Compass

Fluxgate

The Compass
Compass Errors
• Variation
• Due to angular difference in direction to true north and magnetic north poles
• Same for every boat in one area
• Deviation
• Due to magnetic influences aboard boat
• Different for every boat
Understanding Variation
• Polar North vs. Magnetic North
• Earth’s magnetic core does not coincide with geographical north
• Every Chart Will Have 1 to 4 Compass Roses To Indicate Variation Of That Area
• An annual increase in variation occurs due to plate tectonics
• Increase may be 1’ to 9’ or more each year
• Important to use most recent edition of charts
Polar Variation

Variation is the angular difference between the geographic and magnetic meridians

Geographic North Pole

Observer’s position

Magnetic North Pole

Compass
• Points to North Magnetic Pole
• Area that changes slightly
• True North
• Earth’s axis
• Base for latitude and longitude
The Compass Rose

As Seen On The 1210-Tr ChartSouth of Rhode Island = True North

= Magnetic North

Deviation
• Any Magnetic Field Aboard A Vessel Strong Enough To Effect The Compass
• Engines, electronic instruments, wires, steering wheel, especially the radio ‘s speaker
• Deviation is specific to each individual vessel
• Deviation will vary depending upon vessel’s heading
• If more than one or two degrees, a DEVIATION TABLE should be constructed
Correcting Compass Errors

T

Tele-

V

Variation

Vision

M

DOWN

WEST

Makes

D

Dull

Deviation

C

Children

Compass Rose

Compass Review
• Variation
• Local difference, East or West, between the direction of true and magnetic north
• Deviation
• Error caused by magnetic influences within the boat based on its heading
Measuring Distance
• One Degree Of Latitude Equals 60Nautical Miles
• One Minute Of Latitude Equals OneNautical Mile
• Use
• Latitude scale at vertical side of chart, or
• Distance scale
Expressing Course Or Direction
• Can be affected by variation
• Used to plot a course
• Difference from true caused by variation
• Deviation from magnetic heading caused by magnetic influences on boat
• Used to steer a course
• Line of position (LOP)
• Range LOP
• Bearing LOP
• Loran time differential (TD) LOP
• Circle of position (COP)
• Distance from an object
• GPS
Positioning
• Where Two Lines Of Position (LOP) Cross
• Where Two Circles Of Position (COP) cross
• Where one LOP & one distance or COP cross
• Third value to validate
Positioning
• Obtaining an LOP
• Use hand-held compass (bearing)
• Turn vessel so bow is centered on object
• Range: two objects that line up

1400 FIX

1400

260

1400

200

Fixes

Where Two LOPs Cross

Tank

Tower

Measuring Speed
• Speedometers – Give Speed Over Water
• On small boats, not especially accurate
• More Accurate Speed Indication Based on Tachometer Readings (RPMs)
• Still Speed over the Water
• Need Speed Over the Bottom (Ground)
• Takes into consideration the effects of current and wind
• Essential when computing time, speed, and distance problems
• Obtain from fixes or electronic (RADAR, GPS or LORAN)

Direction 2

Direction 1

Average

RPM

Time

Speed

Time

Speed

Speed

800

12 m

5 kts

15 m

4 kts

4.5 kts

1000

10 m

6 kts

12 m

5 kts

6.5 kts

1500

7 m

8.5 kts

8 m

7.5 kts

8 kts

2000

6 m

10 kts

7.5 m

8 kts

9 kts

3000

5 m

12 kts

6 m

10 kts

11 kts

Speed Table

Determining Speed

Vessel Run Over Measured Mile

12

10

8

SPEED (Kts)

6

4

2

0

0

800

1000

1500

2000

3000

Speed Curve

RPM

Computing Distance Speed and Time
• Some Examples:
• Suppose you drive your boat at a speed of 20 Knots for 12 minutes. Howfarhave you gone?
• Howlong does it take to travel 4 Nautical Miles at a speed of 20 Knots?
• How fast are you going if you travel 4 Nautical Miles in 12 minutes?

60 x D

S

T

Speed – Distance - Time

“Sixty D Street” 60D=ST

S=60

T

T=60

S

D=ST

60

Computing Formulas
• Time: T = 60 D /S
• 60 X 4 Miles = 240 / 20 knots = 12 minutes
• Distance: D = (S X T) / 60
• 20 Knots X 12 min = 240 / 60 = 4 Nautical Miles
• Speed: S = 60 D / T
• 60 X 4 Miles = 240 / 12 min = 20 Knots
• Piloting
• Inertial Guidance
• Deduced Reckoning
• Process of determining a ship’s approximate position by applying to the last well determined position, a series of vectors, representing the run that has since been made
• Only TRUE courses are used by the Navy and Coast Guard
• Small boats can substitute magnetic
• Course
• From a known position, line along which a vessel is steered.
• Written as C & three digit number over line and Speed indicated under line by S & two digits
• Fix
• An accurate position usually obtained by crossing 2 or more LOPs. Indicated as circle around dot and a time notation
• 0930 Fix
• DR Position
• Obtained by vessel’s course and speed from the last accurate position
• 0930 DR
• EP – Estimated Position
• Most probable position, determined from bearings of questionable accuracy
• 0930 EP
• A DR Shall Be Plotted -
• Every ½ Hour, on the hour and half hour
• At the time of every course change
• At the time of every speed change
• At the time of obtaining a FIX
• At the time obtaining a single LOP
Plotting Conventions
• Course Line
• LOP
• DR Position
• Fix

C 090

S 10

1445

090

1000

1200

0900

C020

S10

C120

S10

0930

1055

C150

S10

C055

S10

1010

Typical DR Plot
• LORAN
• GPS
• Global Positioning System
• Depth Sounders
Waypoints
• Fixes
• Where you have been
• Where you want to go
• Used by LORAN and GPS
• Entered on the chart
• Verify all tracks on a chart for hazards
LORAN
• Land based antennas
• Chains - masters and slaves
• AM signals
• Some distortion
• Some “holes” in coverage
GPS
• The Choice Of Most Recreational Boaters
• Handheld – Mounted – Plotters
• \$100+
• 24 Orbiting Satellites
GPS Accuracy
• SA – Selective Availability
• Not in use since May 1, 2000
• 15 meters or 49.2 feet 95%
• DGPS – Differential GPS
• Land-based supplement
• 5 meters or 16.4 feet
• WASS – Wide Area Augmentation System
• 2.5 meters or 8.2 feet
• Latest GPS incorporates LORAN as well
Tides
• Tides per day
• Diurnal
• Semi-diurnal
• Mixed
• Monthly
• Spring Tides
• Neap Tides
Rule of Twelve
• One-Two-Three Rule of Thumb
• Tide may rise or fall
• 1/12 1st & 6th Hours
• 2/12 2nd & 5th Hours
• 3/12 3rd & 4th Hours
• Assume a 12 foot tide
• 1st hour = 1 foot
• 2nd hour = 3 feet (1+2)
• 3rd hour = 6 feet (1+2+3)
• 4th hour = 9 feet (1+2+3+3)
• 5th hour = 11 feet (1+2+3+3+2)
Three Key Words

PRACTICE

PRACTICE

PRACTICE

Summary (1)
• Projections
• Vertical Datum: MHW and MLLW
• Piloting Tools
• Latitude - Longitude
• Maps Vs Charts
Summary (2)
• Measuring Distance
• Variation - Deviation
• Lines Of Position - Fixes
• Speed - Time - Distance: 60 D ST