Fore Bearing and Back Bearing Relation
The fore bearing (FB) of a line is its magnetic bearing measured from the preceding station. The back bearing (BB) is the bearing of the same line measured from the current station back towards the preceding station. They indicate opposite directions along the same line.
The relationship is consistently 180° apart:
- If FB < 180°, then BB = FB + 180°.
- If FB > 180°, then BB = FB - 180°.
This confirms the back bearing is exactly 180° opposite to the fore bearing.
Station Angle Calculation
In surveying, especially within traverses, the angles formed at each station are important. The angular difference between consecutive lines is directly linked to these station angles.
The difference between the fore bearing of one line segment and the back bearing of the preceding line segment meeting at a station equals the angle at that station. This angle can be interpreted as either the internal angle or the external angle of the traverse polygon, depending on the measurement convention and the specific geometry.
Therefore, the difference relates to either the internal or external angle at the station.
Important Questions from Compass Surveying and Theodolite
Which of the following statement is CORRECT for whole circle bearing?
Least count of a theodolite is ________
For measurement of vertical angles through theodolite, the instrument should be levelled with reference to the ________ bubble and the ________ clamp that is used to rotate the telescope in the vertical plane.
The following statements given pertain to theodolite used in surveying. Identify the incorrect statement
The use of Electronic Digital Theodolite attached to a total station is to measure:
