In surveying and navigation, forward bearing and back bearing are two terms used to describe directions or angles relative to a reference point. Here’s how they are differentiated:
- Forward Bearing: Forward bearing refers to the angle or direction from a reference point to a target or an object of interest. It indicates the direction in which an observer or surveyor is facing or moving when looking at the target. It is typically measured clockwise from a reference direction, such as north, and expressed in degrees, minutes, and seconds.
- Back Bearing: Back bearing, also known as reverse bearing or reciprocal bearing, is the opposite direction of the forward bearing. It is the angle or direction from a target or object of interest back to the reference point. In other words, it is the bearing obtained by reversing the direction or orientation of the forward bearing. Back bearing is useful for navigating back to a starting point or determining the angle of approach when returning from a target.
To illustrate the difference, let’s consider a surveyor standing at Point A and looking towards Point B:
- The forward bearing would be the angle or direction from Point A to Point B. For example, the surveyor might determine that the forward bearing from Point A to Point B is 45 degrees clockwise from north.
- The back bearing, in contrast, would be the angle or direction from Point B back to Point A. It is the opposite direction of the forward bearing. So, if the forward bearing from Point A to Point B is 45 degrees clockwise from north, the back bearing from Point B to Point A would be 225 degrees (180 degrees + 45 degrees) clockwise from north.
In summary, forward bearing represents the angle or direction from a reference point to a target, while back bearing represents the opposite direction from the target back to the reference point.