Correct Answer - Option 4 : Both (1) and (2)
Offset is the perpendicular distance taken from either side of the chain line running in a particular direction. The purpose of offset is to locate the objects which lie in the vicinity of the main survey line.
In our case, chain line runs along the N-S direction, so offset will be taken either right of N-S direction i.e. towards east side or left of N-S direction i.e. towards west side.
Important Points:
They may be of two kinds – perpendicular and oblique
1. Perpendicular Offset: When these lateral measurements are taken perpendicular to the chain line.
Perpendicular offsets may be taken in the following ways:
i) By setting a perpendicular by swinging tape.
ii) By setting a right angle in the ratio 3: 4: 5.
iii) By setting a right angle with the help of builder square or tri square.
iv) By setting a right angle by cross-staff or optical square.
2. Oblique Offset: Any offset not perpendicular to the chain line is said to be oblique. These are taken when the objects are at a long distance from the chain line or when it is not possible to set up the right angle due to some difficulties. It involves more measurements and difficulties than perpendicular offsets.
