Aquaculture Engineering

Compass surveying - Calculation of angle from bearings

Unit 1- Surveying

Compass surveying

Calculation of angle from bearings

From fig (a) the included angle α between the lines AB and AC is θ₂ - θ₁ = Fore bearing of one line- fore bearing of the other line
It is possible when the bearing being measured from common point A
Fig (b) The angle α = (180° + θ₁) – θ₂
Back bearing of previous line – Fore bearing of next line

Animation-a

Let us consider Reduced Bearing system

From Fig (a) both the bearings have been measured to the same side of common meridian, the included angle α = θ₂- θ₁,
In Fig (b) both the bearing have been measured to the opposite sides of the common meridian = α = θ₁+ θ₂,
From Fig (c)both the bearings have been measured to the same side of different meridians and the included angle α = 180°-(θ₂ + θ₁)
In Fig (d) both the bearings have been measured to the opposite sides of the different meridians and angle α = 180°+ θ₂ – θ₁.

Animation-A
Animation-B
Animation-C
Animation-D