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Lesson 4 - Nautical Charts

Charts

In this lesson, we’ll explore:

  • What they are

  • How to use them

  • Why they’re essential for mariners.

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Key Purposes

  • Source of information:

  • Tool for calculations:

  • Record of navigation: 

 

Chart Scales

  • Large-scale

  • Medium-scale: Coastal navigation.

  • Small-scale

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Paper Charts:

  • Reliable, time-tested, no tech required.

  • Require manual updates to stay current.

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Electronic Charts:

  • Modern standard.

  • Raster Charts: Digital scans of paper charts, non-interactive.

  • Vector Charts: Interactive, real-time updates, GPS-compatible.

  • Always carry a paper backup!

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Chart Projections:

  • Mercator Projection

  • Gnomonic Projection

  • Universal Polar Stereographic (UPS)​​

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Rhumb Lines:

  • Constant compass bearing.

  • Straight line on Mercator charts.

  • Best for shorter routes.

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Great Circles:

  • Shortest route between two points.

  • Appears curved on Mercator charts.

  • Saves time/fuel on long voyages.

 

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Publications:

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  • Updates via Notices to Mariners:

    • Weekly bulletins with instructions for changes.

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  • Block Corrections: 

    • Printable patches for big updates.

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  • Temporary Notices: 

    • Cover short-term changes like exclusion zones.

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  • Tide Tables:

    • Predict tidal rise and fall.

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  • Tidal Stream Atlases:

    • Show tidal current direction and strength.

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  • Lists of Lights:

    • Details on lighthouses and navigational aids.

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  • Radio Signal Lists:

    • Frequencies and communication station details.

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  • Yachtsmen’s Almanacs:

    • Condensed navigation guides for small craft.

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  • Pilots and Sailing Directions:

    • Descriptions of coasts, harbors, and hazards.

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