Definition of a nautical mile – choose the correct geodetic meaning A nautical mile is defined as the length of:

Introduction / Context:
The nautical mile underpins marine and aeronautical navigation. Its geodetic basis links linear distance to angular measures on the Earth, facilitating direct conversion between charted angles and distances.

Given Data / Assumptions:

• Earth approximated by a reference ellipsoid or sphere for the definition.
• One minute of arc = 1/60 of a degree.

Concept / Approach:
By historical and practical convention, a nautical mile corresponds to the length of one minute of arc of latitude along a meridian. This avoids longitude convergence issues (longitude minute varies with latitude) and gives a near-constant distance standard (modern value fixed internationally at 1852 m).

Step-by-Step Solution:
Identify which angular minute has near-constant ground length.A minute of latitude along a meridian provides a consistent standard → nautical mile.

Verification / Alternative check:
Modern definition: 1 nautical mile = 1852 m; this closely matches the mean length of 1 minute of latitude on Earth.

Why Other Options Are Wrong:

• Minute or degree of longitude vary with latitude (zero at poles).
• One degree of latitude is 60 nautical miles, not one.
• Equatorial radius is a length constant, not an angular-based unit.

Common Pitfalls:
Assuming 1 minute of longitude equals a nautical mile at all latitudes; true only at the equator.

Final Answer:
1 minute of latitude