Boating Skills

1
Boating Skills Seamanship

• Lesson 9
• Introduction to Navigation

2
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
• Compute Time,Speed, And Distance

3
Navigators Tools

• Charts
• Magnetic Compass
• Course Plotter Parallel Rulers
• Dividers
• Good Pencils - Erasers
• Binoculars - 7 x 50
• Means Of Finding Water Depth
• Electronic Tools

4
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

5
Chart Projection

• Converts Spherical Area (Earth) To A Flat Piece
  Of Paper (Chart)
• Two Main Types Of Projections
• Mercator
• Conical

6
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

7
A Mercator Projection
Lines of Longitude Projected Parallel
The Further AwayFrom The Equator, The Greater
The Distortion
Spherical Surface Projected On A Cylinder
8
The Polyconic Projection

• Earths 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

9
Conical Projection

• Less Distortion in Northern/Southern Areas

10
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

11
General Information Block
12
Chart Scales

• Large Scale Small Area
• Small Scale Large Area
• 180,000 Smaller Scale Than 140,000
• 180,000 Means 1 INCH On CHART Equals 80,000
  Inches On Earth
• Always Use Largest Scale Possible

13
Chart Scales (Cont)

• Harbor 12,000
• 140,000
• Coast 140,000
• 1150,000
• General 1150,00
• 1600,000
• Sailing 1600,000
• 114,000,000

14
Chart Selection

• Nautical Chart Catalog 1
• Chart Information

15
Chart Datum

• Datum
• Benchmark term from which a charts vertical or
  horizontal measurements are made
• Vertical Clearance
• Based on Mean High Water
• Depth
• Based on Mean Lower Low Water (MLLW)

16
Vertical Chart Datum
Boats Actual Clearance
17
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

18
Latitude and Longitude
Parallels of Latitude
Meridians of Longitude
19
Latitude
20
Measuring Latitude

• Line A-B
• Center of the earth to equator (radius)
• Line A C
• Center of earth to parallel
• Angle 60 º

21
Longitude
22
Measuring Direction

• Use Charts
• 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

23
The Compass

• Top Reading
• Front Reading
• Inclinometer
• Direct Digital
• Telltale Compass
• Fluxgate

24
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
• Changes with boat heading

25
Understanding Variation

• Polar North vs. Magnetic North
• Earths 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

26
Relative Positions of Poles
27
Polar Variation

• Variation is the angular difference between the
  geographic and magnetic meridians

Geographic North Pole
Observers position
Magnetic North Pole
28
Compass

• Points to North Magnetic Pole
• Area that changes slightly
• Far northern Canada
• True North
• Earths axis
• Base for latitude and longitude

29
The Compass Rose
As Seen On The 1210-Tr ChartSouth of Rhode
Island True North Magnetic North
30
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 vessels
  heading
• If more than one or two degrees, a DEVIATION
  TABLE should be constructed

31
Correcting Compass Errors
T
True Heading
Tele-
V
Variation
Vision
M
DOWN ADD WEST
Makes
Magnetic Heading
D
Dull
Deviation
C
Children
Compass Heading
(Add Wonder)
32
True Heading
Compass Rose
33
015 Degrees West Variation
34
005 Degrees West Deviation
35
005 Degrees West Deviation
36
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

37
Measuring Distance

• One Degree Of Latitude Equals 60 Nautical Miles
• One Minute Of Latitude Equals One Nautical Mile
• Use
• Latitude scale at vertical side of chart, or
• Distance scale

38
Expressing Course Or Direction

• True Heading
• Can be affected by variation
• Used to plot a course
• Magnetic Heading
• Difference from true caused by variation
• Compass Heading
• Deviation from magnetic heading caused by
  magnetic influences on boat
• Used to steer a course

39
Finding Your Position

• Line of position (LOP)
• Range LOP
• Bearing LOP
• Loran time differential (TD) LOP
• Circle of position (COP)
• Distance from an object
• RADAR
• GPS

40
Positioning

• To Fix Your Position
• 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

41
Positioning

• Obtaining an LOP
• Use hand-held compass (bearing)
• Turn vessel so bow is centered on object
• Range two objects that line up
• LORAN reading
• RADAR or GPS reading

42
Fixes

• Where Two LOPs Cross

Tank
Tower
43
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)

44
Speed Table
Determining Speed
45
Speed Curve
RPM
46
Computing Distance Speed and Time

• Some Examples
• Suppose you drive your boat at a speed of 20
  Knots for 12 minutes. How far have you gone?
• How long 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?

47
Speed Distance - Time
Sixty D Street 60DST S60 T T60 S DST 60
48
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

49
Primary Methods Of Navigation

• Dead Reckoning
• Piloting
• Celestial Navigation
• Electronic Navigation
• Inertial Guidance

50
Dead Reckoning

• Deduced Reckoning
• Process of determining a ships 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

51
Dead Reckoning (Cont)

• 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

52
Dead Reckoning (Cont)

• DR Position
• Obtained by vessels course and speed from the
  last accurate position
• 0930 DR
• EP Estimated Position
• Most probable position, determined from bearings
  of questionable accuracy
• 0930 EP

53
Dead Reckoning Rules

• 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

54
Plotting Conventions

• Course Line
• LOP
• DR Position
• Fix

C 090 S 10
1445 090
1000
1200
55
Typical DR Plot
56
Electronic Navigation

• LORAN
• Long Range Navigation
• GPS
• Global Positioning System
• Radar
• Depth Sounders

57
Waypoints

• Fixes
• Where you have been
• Where you want to go
• Used by LORAN and GPS
• Entered on the chart
• Entered in the receivers
• Verify all tracks on a chart for hazards

58
LORAN

• Radio Signals
• Land based antennas
• Chains - masters and slaves
• Shipboard receivers
• AM signals
• Degradation in bad weather
• Some distortion
• Some holes in coverage

59
GPS

• The Choice Of Most Recreational Boaters
• Readily available
• Handheld Mounted Plotters
• 100
• 24 Orbiting Satellites

60
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

61
Tides

• Tides per day
• Diurnal
• Semi-diurnal
• Mixed
• Monthly
• Spring Tides
• Neap Tides

62
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 (12)
• 3rd hour 6 feet (123)
• 4th hour 9 feet (1233)
• 5th hour 11 feet (12332)

63
Three Key Words
PRACTICE PRACTICE PRACTICE
64
Summary (1)

• Projections
• Vertical Datum MHW and MLLW
• Piloting Tools
• Latitude - Longitude
• Maps Vs Charts

65
Summary (2)

• Measuring Distance
• Variation - Deviation
• Lines Of Position - Fixes
• Speed - Time - Distance 60 D ST
• Dead Reckoning