Aquaculture Engineering (2+1)

Compass surveying - Calculation of bearings from the angles

Unit 1- Surveying

Compass surveying

Calculation of bearings from the angles
In the case of traverse in which the included angles between successive lines have been measured the bearing of the lines can be calculated provided the bearing of line is also measured. Let α, β, γ, δ be the included angles measured clockwise from back stations and θ₁ be the measured bearing of the line A.B.

The bearing of the next line BC = Bearing of the line AB + included angle at ‘B’ +- 180°= θ₁ + α + 180°
The bearing of the line CD = Bearing of the line BC + included angle at C + 180°= θ₂ + β +_ 180°
The bearing of the line DE = Bearing of the line CD + included angle at D +_ 180° = θ₃ γ +_180°
The bearing of the line EF= θ₅ = Bearing of the line DE + included angle at E +_ 180° = θ₄ + δ +_ 180°

To get the bearing of the next line, add the measured clockwise angles to the bearing of the previous line. If the sum is more than 180°,deduct 180°, if the sum is less than 180° add 180°