BEARING

As earlier stated a bearing of a line is the angle made by the line with respect to a reference direction, the reference direction being called as meridian. The direction shown by a freely suspended and correctly balanced magnetic needle is called magnetic meridian and by a line the horizontal angle made with this meridian is known as magnetic bearing.

With surface of the earth the points of intersection of earth's axis are known as geographic South and North Pole. The line passing through geographic south, north and the point on earth is known as true meridian at that point and the angle made by a line passing through that point is known as true bearing.

Whereas traversing along lines A, B, C, D ..., the bearing of lime AB is known fore bearing of AB and the bearing of BA is known back bearing. Fore bearing and back bearing differ by 180°.