FORE BEARING AND BACK BEARING

• Fore bearing (abbreviated as FB) is the bearing of the line in the direction of progress of survey while back bearing (abbreviated as BB) is the bearing of the line opposite to the direction of progress of survey.
• The difference of FB and BB of a line is always 180° if both the stations are perfectly free from local attractions.

Relationship between fore bearing and back bearing

• If the fore bearing of a line is given, it is possible to determine the back bearing and vice versa.

1. If the fore bearing of a line is given as the whole circle bearing,

Back bearing = Fore bearing + 180°           if F.B. < 180°

and Back bearing = Fore bearing – 180°      if F.B. > 180°