COMPUTATION OF ANGLES

If, at any point bearings of any 2 lines are known, the angle between these 2 lines can be found easily by drawing a neat sketch, and then noting the difference. The process is illustrated with the examples given below.

Example: In a closed traverse with a compass the following bearings were observed. Calculate the interior angles.

Solution: Given figure shows the angles observed. Back bearings of all the lines can be worked out and noted on the figure. Then calculation of interior angles may be carried out easily.

∠A = 150° 00′ - 65° 00′ = 85° 00′

∠B = 245° 00′ - 125° 30′ = 119° 30′

∠C = 305° 30′ - 200° 00′ = 105° 30′

∠D = (360° - 265° 15′) + 20° 00′ = 114° 45′

∠E = (360° - 330° 00′) + 85° 15′ = 115° 15′