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Along the equator, how far apart are the meridians at 150°E and 151°E in nautical miles?

  • A

    1 NM

  • B

    60 NM

  • C

    60 km

  • D

    111 NM

Refer to figure.
The international nautical mile is defined as 1852 meters, which corresponds roughly to 1 minute of arc along a great circle on the WGS 84 ellipsoid.

  • 1° (degree) = 60' (minutes) = 60 NM
  • 1' (minute) ≈ 1 NM

From this, we derive approximate distances for latitude and longitude changes:

A 1° change in latitude along any meridian ≈ 60 NM

A 1' change in latitude along any meridian ≈ 1 NM

A 1° change in longitude along the equator ≈ 60 NM

A 1' change in longitude along the equator ≈ 1 NM

Due to the ellipsoidal shape of the Earth, these distances vary slightly with latitude. However, for syllabus purposes, we accept 1 NM as equivalent to 1' of arc along a great circle.

Using this approximation, longer distances can be calculated:

  • A 90° change in latitude = 90° × 60' = 5400' ≈ 5400 NM

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