Bearings and navigation triangles

Reading a bearing

A bearing is measured clockwise from north at the starting point. Write whole-degree bearings with three digits, such as \(045^\circ\). Parallel north lines make it possible to compare directions at different points.

To reverse a direction, add or subtract \(180^\circ\) to obtain a bearing from \(000^\circ\) to less than \(360^\circ\). For example, the reverse of \(065^\circ\) is \(245^\circ\).

Draw north at each point where a bearing is given. Mark the clockwise angle, then find the angle inside the navigation triangle. Bearings measured at different points cannot simply be subtracted without considering the directions.

In the next diagram, the directions from \(O\) to \(A\) and \(B\) lie on the same side of north, so the angle between them is \(130^\circ-45^\circ\).