The measurement of absolute bearings of fixed landmarks and other navigation aids is useful for the navigator because this information can be used on the nautical chart together with simple geometrical techniques to aid in determining the position of the vessel.Ī grid bearing (also known as grid azimuth) is measured in relation to the fixed horizontal reference plane of grid north, that is, using the direction northwards along the grid lines of the map projection as a reference point.Ī compass bearing, as in vehicle or marine navigation, is measured in relation to the magnetic compass of the navigator's vehicle or vessel (if aboard ship). If the north used as reference is the true geographical north then the bearing is a true bearing whereas if the reference used is magnetic north then the bearing is a magnetic bearing.Īn absolute bearing is measured with a bearing compass. In nautical navigation the absolute bearing is the clockwise angle between north and an object observed from the vessel. Ī compass rose, showing absolute bearings in degrees. įor example, if the bearing between Point A and Point B is S 45° E, the azimuth between Point A and Point B is 135°. For example, if Point B is located exactly southeast of Point A, the bearing from Point A to Point B is 'S 45° E'. The bearing angle value will always be less than 90 degrees. The bearing is expressed in terms of 2 characters and 1 number: first, the character is either N or S next is the angle numerical value third, the character representing the perpendicular direction, either E or W. Thus, it is the same as an azimuth difference (modulo +/- 360 degrees).Īlternatively, the US Army defines the bearing from point A to point B as the smallest angle between the ray AB and either north or south, whichever is closest. Bearings can be measured in mils, points, or degrees. For example, an object relative bearing of 0 degrees would be immediately in front an object relative bearing 180 degrees would be behind.

Relative bearing refers to the angle between the craft's forward direction ( heading) and the location of another object.

For example, an object to due east would have an absolute bearing of 90 degrees. Absolute bearing refers to the angle between the magnetic north ( magnetic bearing) or true north ( true bearing) and an object.The angle value can be specified in various angular units, such as degrees, mils, or grad. In navigation, bearing or azimuth is the horizontal angle between the direction of an object and north or another object. A standard Brunton compass, used commonly by geologists and surveyors to obtain a bearing in the field

Relative bearing and true bearing