What does "magnetic declination" refer to?

Magnetic declination refers to the angle between magnetic north, which is indicated by a magnetic compass, and true north, which is the direction along the Earth's surface towards the geographic North Pole. This angle changes based on geographic location and is crucial for navigation, as it allows navigators to correct compass readings to find their true north direction. Understanding magnetic declination is essential for accurate navigation to ensure that a navigator can effectively plot a course on charts that are oriented to true North.

The other choices do not pertain to navigation concepts that involve direction. For instance, the distance from the coast to the nearest port, the time required for navigation between two points, and the speed of ocean currents involve different aspects of maritime navigation and geography that do not relate to the directionality indicated by magnetic declination.