An example for instrumental error in levelling is

If 'n' is the number of sides, then the total sum of interior angles of a closed traverse should be

Whole circle bearing of a line is preferred to a quadrantal bearing merely because

An obstacle which obstructs both chaining and ranging may be

Offsets are

Drop arrow is used in

A freely floating needle slightly gets inclined to the horizontal anywhere except on the equator. It is called

Straight, parallel and widely spaced contours represent

The length of a traverse line (L) may be obtained by