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Coastal Nav (Session 1)

The Earth and the Navigation Chart

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Coastal Nav – Session 1 (3 Hours)

Learning Outcome IMO 1.1.2

2.1, 2.2 , 2.3, 2.4

On completion the learner should be able to interpret the information on a navigationalchart and apply it to the techniques of coastal navigation.

Session 1

• Locate and identify appropriate navigational charts required for localoperations and for a coastal passage.

• Explain the advantages of using charts drawn on the Mercatorprojection for plotting the ship’s track.

• Explain the principles of position and direction on the earth’s surface

and define the terms used to apply the principles to navigation.

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Coastal Nav ~ S ession 1 – OVERVIEW

Definitions

The Earth 1 Hour

Charts 1 Hour

Course and Distance 1 Hour

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• Navigation getting A to B

• Coastal Nav still insight of land

• Offshore Nav uses time and celestial bodies

• Navigating – Position fixing and adjusting

• Piloting – Combination of nav and conning

• Conning – Visual cues and instructions only

Coastal Nav ~ S ession 1 – DEFINITIONS

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Coastal Nav ~ S ession 1 – THE EARTH

► Earth assumed to be a sphere for navigation

► Rotates West to East about Polar axis► Bulges at equator – ellipsoid.► Flattening (or compression) of ellipsoid

F = Equatorial axis – Polar axis / Equatorial axis► For WGS 84, F = 1/298.2572

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► Earths surface not regular► Geoid – surface assumed to conform to

mean sea level.► Ellipsoid will only conform to Geoid over

limited area.

Coastal Nav ~ S ession 1 – THE EARTH

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Coastal Nav ~ S ession 1 – THE EARTH

► Datums► Each country will use datum that “best fits” Ellipsoid to Geoid► Australia AGD66 – many charts► AGD84 – new datum► GDA94 – Geocentric Datum of Australia – replaces AGD and is

compatible with GPS► GPS uses WGS84 – World Geodetic System 1984.

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Coastal Nav ~ S ession 1 – THE EARTH

► Great Circle – plane passes through centre of Earth, e.g. Equator► Small Circle – plane does not pass through Earths centre

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Geographical Positions

Quoted as Latitude and Longitude

Used to find a position on the Earth’s surface or describe one

Degrees, Minutes, Seconds

Seconds replaced with Decimal of a Minute

33 ° 15 ·2’ S 151 ° 58 ·7’ E

Coastal Nav ~ S ession 1 – THE EARTH

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Coastal Nav ~ S ession 1 – THE EARTH

•Prime Meridian – Meridian of Greenwich.•Meridians run from pole to pole

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LatitudeParallels of Latitude

Equator is a Great Circles, all other Latitudes Small Circles

Angular measurement North or South of Equator to Poles 90 °

D’lat = Difference of Latitude between any 2 points measuredalong a meridian

Coastal Nav ~ S ession 1 – THE EARTH

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Longitude

Meridian of Longitude

Run between the Poles

Are Great Circles

Angular measurement East or West from Prime Meridian 180 °

D’long = Difference of longitude – smaller angular distancebetween two oints measured alon a arallel.

Coastal Nav ~ S ession 1 – THE EARTH

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Mercator Projection

Gnomonic Projection

Chart Scale

Chart Index

Coastal Nav ~ S ession 1 – CHARTS

l

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Mercator Projection

► Cylindrical Projection► Rhumb lines (loxodromes) – straight lines. Cuts all meridians at

the same angle, i.e. a constant compass direction.

Coastal Nav ~ S ession 1 – CHARTS

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Coastal Nav ~ S ession 1 – CHARTS

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Gnomonic Projection

► Projection to a tangent plane► Least distortion at tangent point.► Great Circles shown as straight lines

► Diagram from Wikipedia

Coastal Nav ~ S ession 1 – CHARTS

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Coastal Nav ~ S ession 1 – CHARTS

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Mercator Chart

► Longitude scale is constant► Latitude scale (distance) varies as secant of

latitude► Lat scale = long scale x sec lat

Coastal Nav ~ S ession 1 – CHARTS

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Mercator Chart

► What is the length of 1 minute of latitude ineach of the following latitudes, on a chartwhere 1 minute of longitude is 5mm.

► a) 5 degrees► b) 32 degrees►

c) 60 degrees► d) 90 degrees

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► a) 5.02mm► b) 5.90mm►

c) 10.0mm► d) infinite.

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Chart Scale

► Natural Scale – measure of how much areaa chart covers

► Small scale – e.g. 1:10 000 000. Oceanchart. Enough detail for passage planningonly

► Large scale – e.g. 1:250 000. Coastal chart.Sufficient detail for a coastal passage – main lights and all navigation hazards

► Very Large scale – e.g. 1:7500. Harbourplans. Large amount of detail including allbuoys and beacons.

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TITLE BLOCK

• Country / State / Area

• Chart Name

• Information up to …

• Scale

• Depths and Heights

• Projection

• Authorities Number is outside Boarder

Coastal Nav ~ S ession 1 – CHARTS

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Coastal Nav ~ S ession 1 – CHARTS

Coastal Nav ~ S ession 1 CHARTS

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MAINTENANCE

• Chart correctionsNotices (permanent corrections)Temporary and Preliminary NoticesLatest EditionNAVAREA X Warnings

AUSCOAST Warnings

• Corrections from Chart Agents, Hydrographic Office, WebSite (www.hydro.gov.au)

• Magenta ink for corrections

• Noted outside chart boarder

• Chart correction log

Coastal Nav ~ S ession 1 – CHARTS

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Coastal Nav ~ S ession 1 – CHARTS

Coastal Nav ~ S ession 1 – CHARTS

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Coastal Nav S ession 1 CHARTS

Coastal Nav ~ S ession 1 – CHARTS

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Coastal Nav S ession 1 CHARTS

C t l N S i 1 CHARTS

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Coastal Nav ~ S ession 1 – CHARTS

ECDIS► Electronic Chart Display and Information

System► Meets IMO performance standards► ECS – Electronic Chart System, does not

meet IMO standards► Vector Chart – chart built from electronic

database► Raster Chart – electronic image of paper

chart

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Coastal Nav ~ S ession 1 – CHARTS

ECDIS can be used to meet SOLAS chart

carriage requirements if:► Type approved► Official electronic charts► Appropriate back up system► Operators properly trained► If full vector charts not available, back up

must include paper charts

Coastal Nav ~ S ession 1 – CHARTS

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Coastal Nav ~ S ession 1 CHARTS

ECDIS Training► Use of vector charts – differing symbols and

presentation to traditional charts► Controls► Layering► Limitations of raster charts►

Electronic updating and correction► Integration with other systems, particularlyGNSS

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Course / Direction

Measured in degrees from North 360 degrees clockwise

Using the Compass Rose

Note the Cardinal Points

Points 11 ¼ Degrees (rarely used)

Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

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Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

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Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

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Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

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► Gyro Compass – points to (or close to) TrueNorth

Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

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Coastal Nav ~ S ession 1 COURSE AND DISTANCE

C l N S i 1 COURSE AND DISTANCE

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Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

Coastal Nav ~ S ession 1 – COURSE AND DISTANCE

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Distance1 Sea Mile = 1’ of Arc of Latitude measured at location, 1842.9m

at equator and 1861.7 metres at poles.

Varies due to Earths ShapePolar Circumference = 21 602.52 nmEquatorial Circumference = 21 638.78 nmInternational Nautical Mile = 1852 metres (mean sea mile - 1’ at

Lat 48 ° ) A Cable is a length measurement of 1/10 th of a MileKnot – unit of speed. 1 nautical mile per hour.

C t l N S i 1 COURSE AND DISTANCE

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Coastal Nav ~ S ession 1 – COURSE AND DISTANCE