Navigation

NAU 102

Lesson 4

Chart Scales

Scale – the ratio of a given distance on the chart to the actual distance which it

represents on Earth.

e.g. 1:80,000 or 1/80,000

1 inch on chart = 80,000 inches on Earth

Chart Scales

Scale can be stated by:

e.g. 1:80,000 or 1/80,000

e.g. “2 inches to the mile”

•Ratio or fraction

•A statement

•A graphic scale

Chart Scales

Small Scale = Large Area

e.g.

1/100,000 vs. 1/10,000

Large Scale = Small Area

The larger the scale, the greater the detail.

Chart Production

•National Geospacial-Intelligence Agency (NGA)

Charts are produced by the government

•Formerly National Imagery and Mapping Agency (NIMA)

Charts of foreign waters:

•Lots of other names, too!

Chart Production

•National Ocean Service (NOS)

•Part of National Oceanography & Atmospheric Administration (NOAA)

Charts of US coastal and inland waters:

Chart Numbers

•1 digit – no scaleCharts are numbered with 1 to 5 digits.

•2 digits – 1:9,000,001 and smaller

•3 digits – 1:2,000,001 to 1:9,000,000

(e.g. Chart No. 1)

•4 digits – Special Purpose

(e.g. Plotting Sheets)

•5 digits – 1:2,000,000 and larger

Chart Numbers

•1st digit = Ocean Basin

2 & 3 Digit Charts

•Cover entire (or most of) ocean basins

Chart Numbers

Chart Numbers

•1st digit = Coastal Region

5 Digit Charts•Most common charts, day-to-day use.

(Not the same as Ocean Basin)

•1st & 2nd digits = Subregion

•Digits 3-5 = Specific Location

(Counterclockwise within subregion)

Regions and Subregions

Chart Numbers

Chart Catalogs

•Free

•Produced by NGA and NOS

•Lists authorized sales agents

•Several volumes, by location

•Lists all available charts

Use of the NGA Catalog

• Step One: Review the index of the world’s coastal

regions/subregions.

Example: You are planning to enter Rio de Janeiro, Brazil.

Use of the NGA Catalog

Rio de Janeiro lies in Region 2

Step #2 Locate theSmall-scale Coastal Chart

Use of the NGA Catalog

Use of the NGA Catalog

Step #3 Locate the Harbor Charts

Chart Scales

Charts are classified by Scale

•Used for mid-ocean navigation

Sailing charts < 1:600,000

General charts 1:150,000 to 1:600,000

•Coastwise navigation

•Outside reefs and shoals

Chart Scales

•Inshore coastal navigation

Coastal charts 1:50,000 to 1:150,000

Harbor charts >1:50,000

•Small harbors & anchorages

•Entering Large bays

Chart Stock Numbers

For purchasing and inventory purposes.

•26 = subregion

E.g. 26AHA26230

•26A = portfolio number

•HA = chart series

•26230 = chart number

•HA = harbor•CO = coastal•GN = general•WO = world

Chart Ordering

•Can buy a portfolio

•Can purchase individual charts

(E.g. 26A = General & Harbor charts for 26)

You must have the latest, large scale chart for your location.

•All (or most) charts in a subregion

Chart Editions

You must use the latest chart!

•Date and Edition Number are on the chart

•New editions issued due to many changes

•Current edition number – lower left

•1st Edition date – top center

Chart Editions

Chart Revisions

•Includes latest corrections

Issued when out of stock

•Few, minor corrections

•A new edition not warranted

•Revision date (not number) printed near the current edition number.

Chart Revision Date

Introduction to Navigation

Questions?