The difference between Fore Bearing and Back Bearing of a traverse line is
GATE AG - 2012,
Answer: C
The difference is exactly 180°.
The fore bearing of a line AB is its direction measured at A, looking towards B. The back bearing is the direction of the same line measured at B, looking back towards A. Since these are two opposite directions along one straight line, their whole circle bearings differ by exactly 180°: BB = FB ± 180°.
If the observed difference is not 180°, that signals local attraction at one of the stations or an observation error, and the bearings must be corrected. A difference of 90°, or anything less or more than 180°, never holds for a correctly observed line.
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