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Lesson 3 - Distance, Depth & Height

Distance

At sea, distance is measured in nautical miles or meters.

 

Speed

Mariners measure speed using knots, where 1 knot equals 1 nautical mile an hour.

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Charter Depths​

- Spot Depth

- Contour Lines

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- Drying line 

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Depth & Height

  • Chart Datum

  • Mean High Water Springs (MHWS)

  • Highest Astronomical Tide (HAT)

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Measuring Depth in Practice

Echo sounders are the standard tool. They work by sending high-frequency sound waves to the seabed and measuring the time it takes for the echo to return. This time is then converted into a depth reading.

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Dead Reckoning (DR)

 

Example:

  • Compass reading = 090

  • Distance Traveled in = 6 NM

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