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GB-37-01-001 · Reverse bearings

The bearing of B from A is 328°. Find the bearing of A from B.

Bearings: Calculating a Reverse Bearing Booklet p. 91
Method
1) Draw parallel North lines
2) Use co-interior angles and angles around a point
3) Measure clockwise from North
4) Write three digits
Worked Example (GB-37-01-001)
1)
Draw A, B and the line AB. Draw a North line at each point; the North lines are parallel.
2)
NANB
3)
At A, the smaller angle between North and AB is 360∘−328∘=32∘360^\circ-328^\circ=32^\circ.
4)
Co-interior angles on the parallel North lines sum to 180∘180^\circ: the clockwise angle at B is 180∘−32∘=148∘180^\circ-32^\circ=148^\circ.
5)
Write the clockwise angle as a three-digit bearing: 148∘148^\circ.
Ans = 148°