The difference of level between a point below the plane of sight and one above, is the sum of two staff readings and an error would be produced equal to
Options
A. the distance between the zero of gradient and the foot of the staff
B. twice the distance between the zero of graduation and the foot of the staff
C. thrice the distance between the zero of graduation and the foot of the staff
D. none of the above.
Correct Answer
twice the distance between the zero of graduation and the foot of the staff