In nautical navigation the absolute bearing is the clockwise angle
between north and an object observed from the vessel. 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.
An absolute bearing is measured with a bearing compass.
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.