What is a Rhumb Line?

A rhumb line is defined as a path on the Earth's surface that maintains a constant compass direction. It represents a straight line on a Mercator projection, indicating the angle between the line and the meridian. This means that if a ship were to navigate along a rhumb line, it would do so by steering at the same compass bearing from departure until arrival, even though this may result in a longer distance traveled compared to a great circle route.

The concept of a rhumb line is particularly useful in navigation, as it simplifies the process of steering by allowing mariners to maintain a consistent heading. This is in contrast to other navigation methods, such as great circles, which require continuous adjustments to the heading to account for the curvature of the Earth.

Understanding rhumb lines helps in various aspects of surveying and navigation, especially when working with charts and maps. Unlike globe projections or methods of measuring height, which involve different geometric or measurement principles, the rhumb line centers around directional navigation, making it a fundamental concept in surveying and related fields.