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Performance Task

Smooth Sailing

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Sailors use nautical miles to measure distances and knots to measure speeds.

Sailors use nautical miles to measure distances and knots to measure speeds.

NAUTICAL MILE:

A unit for distance based on the circumference of Earth
$$1$$ nautical mile $$\approx 1.15$$ miles

KNOT:

A knot is one nautical mile per hour.
$$1$$ knot $$\approx 1.15$$ miles per hour

Get Your Bearings

Get Your Bearings

You are navigating a boat to Port A, which is 5.2 nautical miles due east of Port B. You determine that the bearing from your current location to Port A is S 60° E and your bearing to Port B is S 30° W. You travel at an average speed of 24 knots. How long will it take you to reach your destination if you take a direct route?

To avoid an island directly between your location and Port A, you travel due east until your new bearing to Port A is S 40° E. How does this affect your travel time? Justify your answer.


photograph of buoy in water

Did You Know?

  • A nautical mile is based on the circumference of the Earth. Consider the circle that represents the equator of the Earth. Divide that circle into 360 degrees and then divide a degree into 60 minutes. One minute of arc on Earth is one nautical mile. This unit of measurement is used by all nations for air and sea travel.
  • A compass is an instrument used for navigation. Compass bearings indicate a straight line from one position to another.
  • Standard compass bearings are divided into sixteen different directions around the compass, each located 22.5° apart.
  • The four main directions — north (N), south (S), east (E), and west (W) — are called cardinal points on a compass. The directions halfway between cardinal points — northeast (NE), southeast (SE), southwest (SW), and northwest (NW) — are called intercardinal points.  The directions halfway between each cardinal point and intercardinal point are called secondary intercardinal points. They are north-northeast (NNE), east-northeast (ENE), east-southeast (ESE), south-southeast (SSE), south-southwest (SSW), west-southwest (WSW), west-northwest  (WNW), and north-northwest (NNW).

Find Out More – Search Topics

  • Nautical mile
  • Compass
  • Compass bearings