Bearing
A horizontal angle measured clockwise from a chosen reference direction, usually north. It specifies the direction from one point toward another.
Azimuth: A horizontal angle measured clockwise from a reference direction, commonly north. Azimuth is the broader angular convention that includes many bearings.
Protractor: An instrument for measuring or constructing angles, usually marked in degrees. A protractor measures the angle between the reference direction and the target line.
Dead reckoning: A method of estimating position by advancing from a known location using direction, speed, and elapsed time. A measured bearing supplies the direction component of a dead-reckoning estimate.
Heading (navigation): The direction an aircraft or vessel points, expressed relative to a reference direction. A heading describes an object's orientation, while a bearing describes the direction toward a target.
Compass rose: A diagram showing directions around a circle, often marked with cardinal and intermediate points. Its marked directions provide familiar reference axes for bearings.
Great-circle navigation: Navigation along the shortest path between two points on a spherical surface. On a globe, the initial bearing for a great-circle route changes as the route proceeds.
Land surveying: The measurement and mapping of land boundaries, terrain, and positions. Surveyors use bearings to record the directions of boundary lines and traverses.
Course (navigation): The intended direction of travel over the Earth's surface. A course is a planned path direction; a bearing can point toward a specific object or position.
Cardinal direction: One of the four principal compass directions: north, east, south, or west. Bearings often use north as their zero direction and express other directions relative to it.
Inverse tangent: The inverse trigonometric function that returns an angle from a ratio of perpendicular sides. Coordinate differences can yield a bearing through an inverse-tangent calculation with quadrant correction.