# Fore Bearing and Back Bearing | Surveying

## Bearings measured in the direction of progress of survey are known as fore bearing and bearings measured opposite to the direction of survey are known as back bearing.

Bearing of a line is direction with respect to a given meridian; Meridian is a fixed reference line. While setting out a survey line, the bearing readings are necessary

• Fore Bearing - Bearing measured in the direction of progress of survey

• Back Bearing - Bearing measured opposite to the direction of survey

In the figure below, OA is the survey line to be set out.

• Fore Bearing (FB) of OA = θ1

• Back Bearing (BB) of OA = θ2

### Fore Bearing to Back Bearing

BB = FB ± 180°

• Use positive sign of FB < 180°

• Use negative sign of FB > 180°

In reduced bearing system, the angle remains same for FB and BB; Only the quadrants are opposite.

### Example: What is the BB if FB = 250°

BB = FB - 180° (FB > 180°)

BB = 250° - 180° = 70°

In reduced bearing system, FB = S70°W and BB = N70°E

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