What is the purpose of a compass in navigation?

The primary purpose of a compass in navigation is to indicate the direction of magnetic north. This is critical for sailors and navigators, as knowing which way is north allows them to orient themselves and set a course. A compass works by aligning itself with the Earth's magnetic field, providing a reliable reference point that can be used to determine headings, bearings, and general direction in various navigational contexts.

Understanding magnetic north is fundamental for effective navigation and helps in pinpointing one's position relative to other landmarks, coastlines, and navigational aids. It is essential for plotting courses on nautical charts, making adjustments as necessary for factors like magnetic variation, and ensuring safe travel across waterways.

The other options, while related to navigation, do not accurately describe the compass's fundamental role. The compass does not measure speed, calculate water currents and tides, or offer detailed maps; those functions are served by different tools and instruments in the navigator's toolkit.