Lesson 2: Terrestrial Coordinate System and Nautical Charts

Lesson 2: Terrestrial Coordinate Lesson 2: Terrestrial Coordinate System and Nautical ChartsSystem and Nautical Charts

AGENDA:AGENDA:– Terrestrial Coordinate System (Lat/Long)Terrestrial Coordinate System (Lat/Long)– Chart ProjectionsChart Projections– Chart Interpretation/ScaleChart Interpretation/Scale

Lesson 2: Terrestrial Coordinate System and Nautical Charts

Applicable Reading:

Hobbs, Chapter 4Hobbs, Chapter 4

Earth: A “not-so-perfect” Earth: A “not-so-perfect” SphereSphere

GEOGRAPHIC COORDINATE SYSTEMGEOGRAPHIC COORDINATE SYSTEM

LA

TIT

UD

EL

AT

ITU

DE

LONGITUDELONGITUDE

MEASUREMENT OF ARCMEASUREMENT OF ARC

PRONOUNCEDPRONOUNCED SYMBOLSYMBOL

DegreesDegrees (°) (°)

MinutesMinutes (´)(´)

SecondsSeconds (´´) (´´)

•Positions in relationship to Earth’s Coordinates system are expressed in:

LATITUDE PARALLELSLATITUDE PARALLELS

0 °0 °

20 °N20 °N

40 °N40 °N

60 °N60 °N

90 °N90 °N80 °N80 °N

20 °S20 °S

60 °S60 °S

90 °S90 °S

40 °S40 °S

Equator

Longitudinal ParallelsLongitudinal Parallels

Prime Meridian(Greenwich England)

0° Longitude

Longitude:0-180 East

Longitude:0-180 West

Terrestrial Coordinate SystemTerrestrial Coordinate System

A A Great Circle Great Circle is defined as a line on the is defined as a line on the surface of sphere, formed by the intersection surface of sphere, formed by the intersection of a plane passing through it’s center.of a plane passing through it’s center.

EquatorEquator The great circle formed by passing a plane perpendicular to the The great circle formed by passing a plane perpendicular to the

earth’s axis halfway between its poles. earth’s axis halfway between its poles. The equator divides the earth into northern and southern hemispheres The equator divides the earth into northern and southern hemispheres One of the two great circles from which all locations on the earth’s One of the two great circles from which all locations on the earth’s

surface are referenced.surface are referenced.

Prime MeridianPrime Meridian The meridian that passes through the original position of the Royal The meridian that passes through the original position of the Royal

Greenwich Observatory near London, England. Greenwich Observatory near London, England. Constitutes the second reference line for the terrestrial coordinate Constitutes the second reference line for the terrestrial coordinate

system. system. All other meridians are referenced to the prime meridian; it divides All other meridians are referenced to the prime meridian; it divides

the earth into the eastern and western hemispheres.the earth into the eastern and western hemispheres.

Terrestrial Coordinate SystemTerrestrial Coordinate System

A A Small CircleSmall Circle is any other circle formed on is any other circle formed on the surface of a sphere by the intersection of the surface of a sphere by the intersection of a plane not passing through the sphere’s a plane not passing through the sphere’s center.center.

Chart ProductionChart Production

Two government agencies are mainly responsible for Two government agencies are mainly responsible for producing nautical charts - the producing nautical charts - the National Geospatial National Geospatial Information AgencyInformation Agency and the and the National Ocean Service.National Ocean Service.

– National Geospatial Information Agency (NGA)National Geospatial Information Agency (NGA) - concerned - concerned mainly with the production and upkeep of charts and related mainly with the production and upkeep of charts and related navigational publications covering all ocean areas of the world navigational publications covering all ocean areas of the world outside U.S. territorial waters.outside U.S. territorial waters.

– NOAA/National Ocean ServiceNOAA/National Ocean Service - concerned with charts - concerned with charts covering inland and coastal waters of the United States and its covering inland and coastal waters of the United States and its

possessions.possessions.

TERMS AND DEFINITIONSTERMS AND DEFINITIONS

CHART SCALECHART SCALE: : THE RELATIONSHIP BETWEEN TWO THE RELATIONSHIP BETWEEN TWO MEASUREMENTS. EXPRESSED AS A MEASUREMENTS. EXPRESSED AS A RATIO.RATIO.

THE SCALE TO WHICH A CHART IS THE SCALE TO WHICH A CHART IS DRAWN APPEARS DIRECTLY UNDER ITS DRAWN APPEARS DIRECTLY UNDER ITS TITLE.TITLE.

Scale conversion and reference

TERMS AND DEFINITIONSTERMS AND DEFINITIONS LARGE SCALE CHART COVERS A SMALL LARGE SCALE CHART COVERS A SMALL

AREA AND ARE USED FOR PILOTING AREA AND ARE USED FOR PILOTING AND INSHORE NAVIGATION.AND INSHORE NAVIGATION.

TERMS AND DEFINITIONSTERMS AND DEFINITIONS

SMALL SCALE CHARTS ARE LESS SMALL SCALE CHARTS ARE LESS DETAILED THAN LARGE SCALE CHARTS DETAILED THAN LARGE SCALE CHARTS AND COVER A LARGE AREA.AND COVER A LARGE AREA.

Desirable qualities of a chart projection:Desirable qualities of a chart projection:– Maintain Maintain true shapetrue shape of physical features. of physical features.– Maintain Maintain correct proportionscorrect proportions of features of features

relative to one another.relative to one another.– True scaleTrue scale, permitting accurate measurement , permitting accurate measurement

of distance.of distance.

– Rhumb linesRhumb lines plot as straight lines. plot as straight lines.

– Great circlesGreat circles plot as straight lines. plot as straight lines.

Chart ProjectionsChart Projections

MERCATOR PROJECTION:MERCATOR PROJECTION:

The Most Common Projection Used In Maritime The Most Common Projection Used In Maritime Navigation.Navigation.

Point Of Tangency Is The Equator.Point Of Tangency Is The Equator. Rhumb lines plot as STRAIGHT lines.Rhumb lines plot as STRAIGHT lines.

Mercator ProjectionMercator Projection

Mercator ProjectionMercator Projection

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998

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Advantages/Disadvantages of the Advantages/Disadvantages of the Mercator ProjectionMercator Projection

ADVANTAGESADVANTAGES

1.1. Position, distance, and Position, distance, and direction can all be easily direction can all be easily determined determined

2.2. Rhumb lines plot as Rhumb lines plot as straight lines straight lines

3.3. Meridians plot as straight Meridians plot as straight lineslines

DISADVANTAGESDISADVANTAGES

1.1. Distortion of true size of Distortion of true size of surface features surface features increases with distance increases with distance from the equatorfrom the equator

2.2. Great circles, other than Great circles, other than a meridian or the a meridian or the equator, appear as equator, appear as curved lines.curved lines.

Gnomonic ProjectionGnomonic Projection

Advantages/Disadvantages of the Advantages/Disadvantages of the Gnomonic ProjectionGnomonic Projection

ADVANTAGESADVANTAGES

1.1. Great circles appear as Great circles appear as straight lines. straight lines.

2.2. Uused to plot the Uused to plot the optimum great circle optimum great circle route (shortest path) route (shortest path) between two pointsbetween two points

DISADVANTAGESDISADVANTAGES

1.1. Distortion of shape and Distortion of shape and scale increases as the scale increases as the distance from the point of distance from the point of tangency increases.tangency increases.

2.2. Distance and direction Distance and direction cannot be measured cannot be measured directly from a gnomonic directly from a gnomonic projection.projection.

MercatorMercator GnomonicGnomonic

Parallels:Parallels: Straight lines Curved (except Straight lines Curved (except equator)equator)

Meridians:Meridians: Straight Straight Straight Straight

Conformal:Conformal: YESYES NO NO

Great Circles:Great Circles: Curved*Curved* Straight Straight

Rhumb lines:Rhumb lines: Straight Straight Curved lines Curved lines

Applications:Applications: Piloting Piloting Great-circle Great-circle

determinationdetermination

* Except meridians* Except meridians

Chart Projection SummaryChart Projection Summary

Mercator vs. GnomonicMercator vs. Gnomonic

Measuring DirectionMeasuring Direction

All rhumb lines on a Mercator projection All rhumb lines on a Mercator projection represent represent truetrue directions. directions.

Measurement of direction Measurement of direction on a Mercator chart is on a Mercator chart is accomplished by using a accomplished by using a parallel rulerparallel ruler to transfer the to transfer the direction of a rhumb line to direction of a rhumb line to a nearby compass rose.a nearby compass rose.

Distance of 1 NM

1 Degree = 60 NM (Nautical Miles)

1 Minute =1 Nautical Mile

MEASURING DISTANCEMEASURING DISTANCE

DISTANCE ALWAYS MEASURED ON LATITUDE SCALE!

TYPES OF CHARTSTYPES OF CHARTS

GENERAL CHARTSGENERAL CHARTS:: Small Scale ChartsSmall Scale Charts

– 1:150,000 - 1:600,0001:150,000 - 1:600,000

Used for voyage planning.Used for voyage planning.


SAILING CHARTSSAILING CHARTS:: Small Scale ChartsSmall Scale Charts

– 1:600,000 - SMALLER1:600,000 - SMALLER

Used For Open Ocean Navigation.Used For Open Ocean Navigation.


COASTAL CHARTSCOASTAL CHARTS:: Large Scale ChartsLarge Scale Charts

– 1:50,000 - 1:150,0001:50,000 - 1:150,000

For approaching bays and harbors and For approaching bays and harbors and used for coastal navigation outlying used for coastal navigation outlying reefs and shoals.reefs and shoals.


HARBOR AND APPROACH CHARTSHARBOR AND APPROACH CHARTS:: Large Scales ChartsLarge Scales Charts

– 1:2,400-1:50,0001:2,400-1:50,000

Used Primarily For Inshore Navigation Used Primarily For Inshore Navigation and for Navigating Large Inland and for Navigating Large Inland Waterways.Waterways.

CHART NUMBERING SYSTEMCHART NUMBERING SYSTEM

Designed For Use By The U.S. Navy Designed For Use By The U.S. Navy and U.S. Coast Guard.and U.S. Coast Guard.

Built by Defense Mapping Agency Built by Defense Mapping Agency (DMA) who has changed it’s name to:(DMA) who has changed it’s name to:

NATIONAL GEOSPATIAL-INFORMATION NATIONAL GEOSPATIAL-INFORMATION AGENCY (NGA)AGENCY (NGA)

Chart Numbering SystemChart Numbering System

All charts produced by NIMA and NOS are assigned a All charts produced by NIMA and NOS are assigned a number from one to five digits, according to the number from one to five digits, according to the scalescale and and area they depict. area they depict.

# of digits# of digits ScaleScale

1 No scale involved (supporting pub)1 No scale involved (supporting pub)

2 1 : 9,000,001 and smaller2 1 : 9,000,001 and smaller

3 1 : 2,000,001 to 1 :1,900,0003 1 : 2,000,001 to 1 :1,900,000

4 Miscellaneous and special, non-navigational 4 Miscellaneous and special, non-navigational chartscharts

5 1 : 2,000,000 and larger5 1 : 2,000,000 and larger

The chart numbering system also allows the navigator to The chart numbering system also allows the navigator to organize his/her charts into chart portfolios. organize his/her charts into chart portfolios.

Ocean Basins of the WorldOcean Basins of the World

ONE DIGIT CHARTS(1-9)ONE DIGIT CHARTS(1-9)

Have no Scale Connections.Have no Scale Connections.

Comprise The Symbol And Comprise The Symbol And Abbreviation For Charts of The United Abbreviation For Charts of The United States And Other Nations.States And Other Nations.

TWO AND THREE DIGIT CHARTSTWO AND THREE DIGIT CHARTS

Covers Very Large Areas Such As:Covers Very Large Areas Such As:– Entire Ocean BasinsEntire Ocean Basins– Portions of Ocean Basins.Portions of Ocean Basins.

The World’s Water Are Divided Into The World’s Water Are Divided Into Nine Ocean Basins.Nine Ocean Basins.

Coastal Regions of the WorldCoastal Regions of the World

FOUR DIGIT CHARTSFOUR DIGIT CHARTS

Covers Numbers From 5000 to 9999Covers Numbers From 5000 to 9999

Non-navigational, Special-purpose Non-navigational, Special-purpose Charts Such As:Charts Such As:– Special World ChartsSpecial World Charts– Plotting SheetsPlotting Sheets

FIVE DIGIT CHARTSFIVE DIGIT CHARTS(11000-99999)(11000-99999)

Covers Portions Of Coastlines.Covers Portions Of Coastlines.

Most Common Type of Charts By Most Common Type of Charts By Navigators.Navigators.

Majority of Nautical Charts Found Majority of Nautical Charts Found Aboard ShipsAboard Ships

CHART NUMBERINGCHART NUMBERING

The Five Digits Combined Make Up The Alpha-The Five Digits Combined Make Up The Alpha-numeric (Words& Numbers) Prefix.numeric (Words& Numbers) Prefix.

First Two Digits Are The Sub-region.First Two Digits Are The Sub-region.

Third Digit Is The Portfolio Assignment Number.Third Digit Is The Portfolio Assignment Number.

PORTFOLIO ASSIGNMENTPORTFOLIO ASSIGNMENT

““A” Portfolio Consist Of:A” Portfolio Consist Of:

– All Operating Area Charts All Operating Area Charts – Principal Coastal ChartsPrincipal Coastal Charts– Harbor And Approach Charts.Harbor And Approach Charts.

The Navy Has Three Portfolio Assignments A, B, and X.

““B” Portfolios Supplement the “A” B” Portfolios Supplement the “A” Portfolio With:Portfolio With:

– Additional Coastal ChartsAdditional Coastal Charts– Harbor And Approach Charts Harbor And Approach Charts – For Each Sub-region.For Each Sub-region.


““X” Portfolio:X” Portfolio:

– Designated Standard Nautical Charts Designated Standard Nautical Charts Which Have Not Been Assigned To Either Which Have Not Been Assigned To Either an “A” Or “B” Portfolio.an “A” Or “B” Portfolio.


CHART NUMBERINGCHART NUMBERING

The Fourth And Fifth Digits Of The The Fourth And Fifth Digits Of The Prefix Specify The Type Of Chart:Prefix Specify The Type Of Chart:

““CO” - COASTAL CHARTSCO” - COASTAL CHARTS““HA” - HARBOR AND APPROACH HA” - HARBOR AND APPROACH

CHARTS.CHARTS.““OA” - OPERATING AREA CHARTOA” - OPERATING AREA CHART““WO” - WORLDWO” - WORLD““NR” - NAVY RESTRICTEDNR” - NAVY RESTRICTED““GN” - GENERALGN” - GENERAL““TR” - TRAININGTR” - TRAINING

NATIONAL GEOSPATIAL-NATIONAL GEOSPATIAL-INFORMATION AGENCY INFORMATION AGENCY

(NGA)(NGA)NGA STOCK NUMBERNGA STOCK NUMBER Note: The Complete NGA Stock Number Note: The Complete NGA Stock Number

Must Be Used When Requisitioning Must Be Used When Requisitioning Charts And Publications.Charts And Publications.

CHART 12245CHART 12245

(1) First Digit Of A Five Digit Chart Is The (1) First Digit Of A Five Digit Chart Is The Region.Region.

(12) First And Second Digit Combined (12) First And Second Digit Combined Indicate The Sub Region.Indicate The Sub Region.

(245) Last Three Digits Are Numbered (245) Last Three Digits Are Numbered COUNTERCLOCKWISECOUNTERCLOCKWISE Around The Around The Continents.Continents.

(1) First Digit Of A Five Digit Chart Is The (1) First Digit Of A Five Digit Chart Is The Region.Region.

(12) First And Second Digit Combined (12) First And Second Digit Combined Indicate The Sub Region.Indicate The Sub Region.

(245) Last Three Digits Are Numbered (245) Last Three Digits Are Numbered COUNTERCLOCKWISECOUNTERCLOCKWISE Around The Around The Continents.Continents.

Chart Correction SystemChart Correction System Chart corrections are disseminated via Chart corrections are disseminated via Notice to Notice to

MarinersMariners and and Local Notice to MarinersLocal Notice to Mariners. .

Notice to Mariners - issued by NGA and contain changes relating Notice to Mariners - issued by NGA and contain changes relating to oceanic and coastal areas worldwide.to oceanic and coastal areas worldwide.

Local Notice to Mariners - issued by the U.S. Coast Guard Local Notice to Mariners - issued by the U.S. Coast Guard districts and contain changes pertaining only to U.S. inland waters.districts and contain changes pertaining only to U.S. inland waters.

Navigators are not required to immediately enter Navigators are not required to immediately enter changes on every chart. changes on every chart.

Corrections are entered on correction cards when received. The Corrections are entered on correction cards when received. The navigator’s staff updates the charts when the ship is scheduled to navigator’s staff updates the charts when the ship is scheduled to operate in an area covered by the chart portfolio. operate in an area covered by the chart portfolio.

REVIEWREVIEW

What is a Great Circle?What is a Great Circle? What is a Small Circle?What is a Small Circle? 2 degrees of Latitude is = how many nm?2 degrees of Latitude is = how many nm? What is the difference between a Mercator What is the difference between a Mercator

and Gnomic projection?and Gnomic projection? Distance is always measured on the Distance is always measured on the

LATITUDE Scale.LATITUDE Scale.

Documents

Lesson 2: Terrestrial Coordinate System and Nautical Charts