Which line maintains a constant bearing along its entire length?

• A. Loxodrome
• B. Orthodrome
• C. Mercator Projection
• D. Cylindrical Projection

Answer: (A)

A line that keeps the same compass direction along its entire length is a loxodrome, also called a rhumb line. The key feature is that the angle between the path and every meridian stays constant, so the bearing you follow doesn’t change as you travel. This is exactly what constant bearing means in navigation. By contrast, a great-circle route (the shortest distance between two points) changes bearing along the way, even though it’s the shortest path. On a Mercator map, rhumb lines plot as straight lines, which is why such charts are handy for plotting a constant compass course. The other terms refer to map projections or to the shortest-path concept, not to a path with unchanging bearing on the globe.