Chart Navigation & Plotting · Sailings — Great Circle vs Rhumb Line
On a long east-west ocean passage at high latitude, why is a great-circle track shorter than the rhumb-line track between the same two points?
- AThe great circle maintains a constant course
- BThe rhumb line ignores the Earth's curvature
- CThe great circle is the shortest distance on a sphere; the rhumb line crosses each meridian at a constant angle and is longer✓ Correct
- DThe two are equal except near the equator
Explanation
A great circle is the shortest path between two points on a sphere but requires continuous course change. A rhumb line holds a constant course (crossing every meridian at the same angle) but is longer; the saving grows with latitude and east-west extent.
Authority: Bowditch (Pub. No. 9), great-circle and rhumb-line sailing
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