What is the term for the angular difference between grid North and magnetic North?

The angular difference between grid North and magnetic North is referred to as declination. Declination is essential for navigation, as it indicates how much magnetic North differs from true North, which is represented by grid North. This difference can vary depending on the location on Earth and is crucial for accurate compass readings and map navigation.

Understanding declination is important for effective navigation, particularly in operations where precision is necessary for orientation and maneuvering. It helps ensure that navigators can adjust their readings and maintain accuracy in their positioning, especially when using compasses in conjunction with grid maps. Knowing the declination allows personnel to convert between magnetic and true heading, facilitating better decision-making in various tactical situations.

The other terms provided do not accurately describe this specific relationship: the G-M angle refers generally to the concept but is not as widely used as the term declination; azimuth typically refers to the angle between a point of interest and a reference direction, and orientation is a broader term related to the position relative to a reference frame.