Which line on a map is defined as having a constant direction relative to all meridians?

Which line on a map is defined as having a constant direction relative to all meridians?

• A. Rhumb line
• B. Great circle
• C. Meridional line
• D. Latitude line

Answer: (A)

A line with a constant bearing relative to every meridian is a rhumb line. This means as you move along it, the angle it makes with any longitude line stays the same, so your compass direction doesn’t drift. On many maps, especially Mercator projections, rhumb lines appear as straight lines, which is why sailors and navigators use them to maintain a steady heading.

The other options describe different geometric ideas. A great circle is the shortest path between two points on a sphere, but its bearing changes as you travel, so it does not maintain a fixed angle with all meridians. A meridional line runs along a single longitude, not crossing all meridians with a constant angle. A latitude line (parallel) stays at a fixed latitude and runs east–west, but the defining property here is about crossing meridians at a constant angle, which is the essence of a rhumb line.