True Bearing and Reduced Bearing:
True Bearing
The geographical north of earth is different from the magnetic north. Hence, the angle which the survey line makes with the true geographical north is termed as true bearing of the survey line.
Arbitrary Bearing
It is the horizontal angle which a survey line makes with any arbitrary meridian, which is any convenient direction towards a permanent and prominent mark or signal, such as a church spire or top of a chimney. Such bearings are used to determine the relative position of line in a small area.
Whole Circle Bearing (WCB)
The complete circle of angular measurement starts with north as 0o and ends at north at 360o. The bearing of line directly obtained by magnetic needle ranging from 0o to 360o is called whole circle bearing.
Reduced Bearing (RB)
The more convenient way to comprehend the direction of a survey line is to represent the bearing on a quadrantal system. The angle is measured with respect to N-S line towards east or west as shown in Figure.
Fore Bearing (FB)
The angle measured in the direction of survey line from starting survey station to the next station is called fore bearing. In Figure, if the bearing of line AB is measured from A towards B, it is known as forward bearing or fore bearing.