Seminar Series

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Welcome

How to Use a Chart

Presented by United States Power Squadrons®

All Maps and Charts courtesy of MapTech

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Welcome

I am Harry Hebb, SNAlso Ron Swope, SN

Presented by United States Power Squadrons®

All Maps and Charts courtesy of MapTech

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How to Use a Chart

This Seminar is intended to serve as an introduction to basic chart symbols and use.

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Chart Symbols Chart References Compass Rose Locating a position

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The Marine Chart

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Sources of Charts

Hydrographic Offices- U.S. – NOAA – NOS - U.K. – British Admiralty Charts- other…

Commercial- Maptech- Richardson’s- other…

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More Detailed Information

For a complete list and explanation of all NOAA chart symbols, consult NOAA Chart Number 1, Nautical Chart Symbols Abbreviations and Terms … over 100 pages in the most nauseous of detail. Currently on-line only.

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What Charts Show Navigators

Above the Water>>

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White

Blue

Green

Gold

Magenta

Colors Used on Charts

Deep, safe water

Shallow water

Areas covered at high water, bare at low water. Green buoys

Dry land, above mean high water

Lighted aids, boundary lines for special areas

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Features Above the Water

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Chart Information

Horizontal (position) Datum

Source Chart

Correction Date

Depth Units

Chart Scale

Mileage Scale

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NM = 6,076.1155 ft

WGS .. World Geodetic System

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Chart Features

Compass Rose

Variation Reference

AnnualChange

MagneticScale

True North

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Chart Scales

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Chart Scales

Charts are scaled representations- Scale is expressed as a ratio

• Example: 1:40,000:- One inch on chart = 40,000 inches on Earth (.6 nm)

- Typical scales• Sailing Chart 1: 600,000 … ? Small Scale• General Chart 1: 200,000• Coastal Chart 1: 80,000• Harbor Charts 1: 40,000

1: 20,000 1: 10,000 1: 5,000 ……. ? Large Scale

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Small Scale Chart - 1:1,200,000

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Coastal Chart – 1:80,000

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Harbor Chart – 1:40,000

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Harbor Chart – 1:20,000

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Harbor Chart – 1:10,000

Large Scale Chart

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What Charts Show Navigators

Below the Water

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Charts Help Us “See” What’s Below

Courtesy Maptech >>

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Features Below the Water

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Depths

Depth Soundingsat true position

[vertical numbers]

Drying heights above chart datum (green)[number is underlined]

Least depth inNarrow channel[number in parentheses]

No bottomat depth shownSOUNDINGS

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Depths

Limit of dredged channel

Unsurveyedor inadequately

surveyed area

Depth & year of latest control survey

FAIRWAYS, AREAS

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Nature of the Seabed

Stones, gravel or shingle

Green: area that covers and uncovers

Rocky area

Coral reef

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Land, Rocks, Wrecks & Obstructions

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Depths and Heights

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Charted Depth

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Aids to Navigation(ATON)

Son of ATOM … he, he

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Navigation Chart Symbols

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Navigation Aid Symbols

Chart vs.

Reality

The object as it appears on the water is shown to the left of its symbol

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Finding Your Wayby using Piloting

Piloting typically refers to navigation by using land based objects as opposed to

celestial bodies.

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Mercator Projection Chart

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Mercator Projection Chart

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Latitude and Longitude

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Coordinates

W Longitude

Latit

ude

N

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Measure Latitude

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Measure Longitude

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Measure Course

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Compass Rose

Variation Reference

AnnualChange

MagneticScale

True North

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Chart Features

MagneticPoles

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Chart Features

Magnetic Variation

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Chart Features

Magnetic Variation

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Chart Features

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Chart Features

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MagneticDeviation

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Chart Features

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MagneticDeviation

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True versus Magnetic Difference is called “Variation”

- Location of Magnetic North changes over time Variation

- East Coast - Magnetic North is to the West of True- West Coast - Magnetic North is to the East of True

Source of Information- Compass Rose- Variation –

• Amount – East or West‘as of [date]’ and ‘annual change’

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True versus Magnetic T … true

V … variation

M … magnetic

D … deviation

C … compass

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True versus Magnetic T … true

V … variation

M … magnetic

D … deviation

C … compass

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True Virgins Make Dull Company … Add Whiskey

+ W or – E … from True to Comp

- W or + E … from Comp to True

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True versus Magnetic T … ??

V … 4 W

M … ??

D … 0 deg

C … 360 deg

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Compass Rose

Variation Reference

AnnualChange

MagneticScale

True North

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Planning on Your Chart

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Planning

You are here (START)

You want to go here (DESTINATION)

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Planning

Travel from Point A to Point B – “Easy? Right?”

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Planning

Shallow Water

Before you start – Check your Chart>>

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What’s in Your Way?

Destination

Shallow Water

start

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Selecting a Safe Path

The direct path goes over a shoal – plan a safer passage.

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What is a Good Path?

A careful scan along the path from Start to Destination will indicate features that will bar safe passage.

Clearly, careful Planning and a current Chart are essential tools for a navigator.

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Chart and GPS Position Accuracy

Chart Correction Date:

• The older your Chart, the more differences between your Chart and reality!

• Check Notices to Mariners (now on-line)>>

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Chart Accuracy

Environmental Factors:

• Large storms or just the daily effects of wind, tide, et cetera, cause coastal areas to be in a constant state of change.

• When in doubt, check the latest obtainable information and sources.

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Questions ? … Comments

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Joining USPS…

Seminar Series

…and don’t forget to wear your life jacket

United States Power Squadrons ®

Expand your knowledge and enhance your enjoyment of recreational boating by …