What is the term for the difference between magnetic north and true north?

The difference between magnetic north and true north is referred to as magnetic declination. This term describes the angle, measured in degrees, between the direction of magnetic north (the direction a magnetic compass points) and true north (the direction along the Earth's surface towards the North Pole). Understanding magnetic declination is crucial for navigation and surveying, as it helps surveyors adjust their measurements to account for the variation between the magnetic field and true geographic orientation.

The concept of magnetic declination is essential for accuracy in various applications, including map reading and GPS use, as knowing the declination allows for corrections to be made when translating between magnetic bearings and geographic bearings. This knowledge ensures that surveyors can provide accurate land surveys, which is vital for legal and construction purposes.

The other terms listed, such as spherical excess, angle of repose, and geoid, refer to different concepts unrelated to the difference between magnetic north and true north, further highlighting the specific relevance of magnetic declination in navigation and surveying.