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Navigation NAU 102 Lesson 4
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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
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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
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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.
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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!
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Chart Production National Ocean Service (NOS) Part of National Oceanography & Atmospheric Administration (NOAA) Charts of US coastal and inland waters:
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Chart Numbers 1 digit – no scale Charts 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
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Chart Numbers 1 st digit = Ocean Basin 2 & 3 Digit Charts Cover entire (or most of) ocean basins
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Chart Numbers
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1 st digit = Coastal Region 5 Digit Charts Most common charts, day-to-day use. (Not the same as Ocean Basin) 1 st & 2 nd digits = Subregion Digits 3-5 = Specific Location (Counterclockwise within subregion)
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Regions and Subregions
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Chart Numbers
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Chart Catalogs Free Produced by NGA and NOS Lists authorized sales agents Several volumes, by location Lists all available charts
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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.
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Use of the NGA Catalog Rio de Janeiro lies in Region 2
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Step #2 Locate the Small-scale Coastal Chart Use of the NGA Catalog
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Step #3 Locate the Harbor Charts
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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
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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
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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
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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
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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 1 st Edition date – top center
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Chart Editions
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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.
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Chart Revision Date
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Introduction to Navigation Questions?
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