Test: Compass Surveying & Theodolite - 2 - Civil Engineering (CE) MCQ

If the fore bearing of a line is given as the quadrantal bearing, then back bearing is numerically equal to the fore bearing. However N changes to S and Exchanges to W and vice versa.

Note that negative (W) declination should be added to quadrantal bearing in second and fourth quadrant i.e. NθW or SθE and it should be subtracted from quadrantal bearing in first and third quadrant i.e., NθE and SθW. Reverse should be done for positive (E) declination.

True bearing = S 25° 20'E + 5°40'
= S 31° 0'E

As the difference between F.B. and B.B. of line AB is exactly 180°, stations A and B are free from local attraction which is not the case with line CD.
Hence stations C and D are affected by local attraction.

BB of AB = FB + 180°
= 35° + 180° = 215° 
∴ included angle between line,
AB and BC = 360° - 215° + 15° = 160°

True bearing
= Magnetic bearing + Declination
∴ 180° = 184° + Declination
or Declination = -4° = 4°W