Navigation Course

1
Navigation Course
2
About Me
Joined BP Tankers when left school worked my up
from Navigating Cadet to Chief Officer over 12
years. These are some of the ships I served on.
3
Introduction

• Magnetic compass work
• Tides
• Buoyage
• Chart work
• Passage planning

4
Magnetic Compass

• Device to point to a fixed point
• Requires no power
• Subject to errors
• Variation
• Deviation
• Compass error

5
Variation

• Magnetic effect of the planet
• Difference between TRUE north and MAGNETIC north
• Changes with time
• Changes with location
• Obtain value from chart
• Once value known apply

6
Deviation

• Magnetic effect of ship or boat or carried
  equipment. (Demo)
• Difference between MAGNETIC north and COMPASS
  north
• Changes with direction travelled
• Keep as far away from ferrous objects as possible
• Calculate the deviation and apply

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Deviation- Deviation Curve
8
How Many Norths?
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Compass Error

• Difference between TRUE North and COMPASS North
• Named EASTERLY or WESTERLY

COMPASS ERROR DEVIATION OR - VARIATION
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Compass Error
Compass
True
to
Add East
CADET
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Compass Error
Remember Difference between true North and
Compass North Compass Error Compass to True Add
East - CAdET
W
E
True Course 045 T
Compass Course 055 C
What is the Compass Error?
What is the Compass Course to steer?
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Deviation, Variation, Compass Error
Remember Difference between true North and
Magnetic North Variation, and difference
between Magnetic North and Compass North
Deviation. Difference between Compass North and
True North Compass Error. Compass to True Add
East - CAdET
Deviation 3E, Variation 7½W, True Course
045T What is compass error? What is the compass
course to steer?
Variation 7½ W
Deviation 3 E
W
E
Compass Course 049½ C
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Put It All Together
Deviation 4½W, Variation 3W True Course
310T Observed three compass bearings 035C,
082C 125C _at_ 1130.
What is the compass error?
Variation 3 W
What is the compass course?
Deviation 4½ W
What are the true bearings to plot?
Compass Course 317½ C
W
E
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Put It All Together
Compass bearing 146C True bearing 134T True
Course 215T Variation 7½W
What is the compass error?
Compass brg 146 C
What is the compass course?
What is the deviation?
True brg 134 T
Variation 7½W
Compass Course 227 C
W
E
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Summary- Magnetic Compass

• Device to point to a fixed point
• Compass Error Compass North
• Variation- Magnetic North
• Deviation
• How to apply and calculate

16
Tides
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Tides

• What causes tides
• Types of tides
• Tidal heights definitions
• Tidal heights calculations
• Tidal streams

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What Causes Tides

• The gravitational pull of the moon
• The gravitational pull of the sun
• Rotation of the earth

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Types of Tide

• Spring Tides
• Sun and Moon pulling together
• Highest of the highs and lowest of the lows
• New Moon, full moon
• Roughly every fortnight

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Types of Tide

• Neap Tides
• Sun and Moon at right angles to the earth
• Lowest of the highs and highest of the lows
• 1st quarter, 3rd quarter
• Roughly every fortnight

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Switch to Macro
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Tidal Definitions

• MHWS Mean High Water Springs
• Average height of high water above chart datum of
  Spring Tides
• MHWN Mean High Water Neaps
• Average height of high water above chart datum of
  Neap Tides
• MLWS Mean Low Water Springs
• Average height of low water above chart datum of
  Spring Tides

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Tidal Definitions

• MLWN Mean Low Water Neaps
• Average height of low water above chart datum of
  Neap Tides
• HAT Highest Astronomical Tide
• Highest height of High Water above chart datum
  ever recorded
• LAT Lowest Astronomical Tide
• Lowest height of Low Water above chart datum ever
  recorded Usually Chart datum

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Tidal Definitions

• HW High Water
• Highest height of tide on a given tide
• LW Low Water
• Lowest height of tide on a given tide
• TIDAL RANGE
• The amount of lift of water on a given tide
• Difference between height of high water and low
  water

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Tidal Definitions

• Height of Tide
• The height of water level above chart datum at a
  given time
• Chart Datum
• The level from which all soundings are measured
  on a chart. The level of which heights of tide
  are measured above
• Drying Heights
• If tide drops to chart datum then sea bottom
  would be above water level

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Tidal Calculations

• Where to get information
• Internet
• Admiralty http//easytide.ukho.gov.uk/Easytide/E
  asyTide/index.aspx
• BBC - http//www.bbc.co.uk/weather/coast/tides/
• Local websites

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Tidal Calculations

• What we need
• Times of high water
• Times of low water
• Heights of high water
• Heights of low water
• If possible graph of tide

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Tidal Calculations
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Tidal Calculations
Depth of water from chart 3.2m Height of tide
2.5m Draft 0.5m How much water underneath us?
Underwater clearance depth from chart height
of tide draft Underwater clearance 3.2m
2.5m 0.5 Underwater clearance 5.2m
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Tidal Calculations
The sill of a lock to enter Avonmouth on the 12
March 2008 has a drying height of 2.4m. In a
vessel with a draft of 1.25 m which must have an
underwater clearance of 1.0m at all times, what
is the earliest and latest time in daylight we
can cross the sill?
Min height of tide 4.65m
0625
1435
Earliest time 0625
Latest time 1435
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Tidal Calculations
The sill of a lock to enter Avonmouth on the 12
March 2008 has a drying height of 2.4m. In a
vessel with a draft of 1.25 m which must have an
underwater clearance of 1.0m at all times, what
is the earliest and latest time in daylight we
can cross the sill?
Min height of tide 4.65m
The Twelfth Rule
Earliest time 0630
1st hour 1/12th of range 2nd hour 2/12th of
range 3rd hour 3/12th of range 4th hour
3/12th of range 5th hour 2 /12th of range 6th
hour 1/12th of range
Latest time 1434
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Tidal Calculations
The charted depth of a wreck off Plymouth is 25m.
Slack water starts 20min before to 20 min after
high water. What max depth of water to dive, and
when can we dive. Date Saturday 15 March 2008.
High Water time 1125
Start of dive 1105
Finish of dive 1145
Height of tide at HW 4.2m
Charted depth 25.0m
Max depth depth 29.2m
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Tidal Streams

• Tide coming in on the flood
• Tide going out on the ebb
• Change over period from in to out, and from out
  to in slack water
• Info on charts or tidal atlas for area

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Tidal Streams

• For a standard port nearby
• Gives direction
• Gives speed for neap spring tides
• For each hour of a tide

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Passage Plan
Passage Plan Date __________ From __________
To ____________ Voyage Number _____
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Fleetwood 16/03/08
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(No Transcript)
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Boat Launch Info- Knott End
Ramp Description Charges 8 per day (pay ferry
man) or 50 plus vat per year. Slope is easy for
a conventional car. Slipway is cleaned by ferry
staff when operational but can still have a layer
of muddy silt on lower area. Ramp is usable
throughout the tide on neap tides but water
leaves the end of the ramp at low water springs
(if low water height below 2.4m). Water on ramp
can be rough as water floods in over the concrete
skeer to seaward side. Maybe a good idea to try
launching over the side of the slipway in these
conditions.
Ramp Type Concrete, lower section cobbled.
Upper Area Concrete
Lower Area Mud
Suitability Large trailer needs a car
Ramp Length 3/4 tidal
Charges 8 daily charge.
Facilities Cafe and toilets at top of slip,
large free public car park to rear of cafe.
Cruising Area Morecambe Bay with access to and
Irish Sea.
Navigational Hazards At low water sand spit
straight off ramp end can be avoided by turning
upriver to first red buoy. Be aware that this
buoy is moored to a large concrete block which is
a real hazard in itself at low water and could
take your gearbox off! Passenger ferry uses
upriver side of ramp and there are large
container ships in the channel. Very strong tidal
currents. Many drying banks outside the buoyed
channel.
http//www.boatlaunch.co.uk/