Civil Engineering - Surveying - Discussion

In levelling, when determining the difference in elevation between a point below and a point above the line of sight, the readings are taken from a levelling staff. If the staff is not held vertically or if there's a misalignment in the zero of graduation (the point from which measurements begin), an error is introduced.

The apparent difference in level becomes the sum of the two staff readings.

However, due to the misalignment, the error introduced is twice the distance between the zero of graduation and the foot of the staff.

This is because the error affects both the lower and upper readings equally, and when summed, it doubles.

Not clear. Please explain to me in detail.

@Sameer Sopori.

Pleese elaborate it clearly.

The minor distance between the bottom graduation and staff bottom (graduation is usually like E shapes on staff, each arm of E equal to 1cm on staff) , For each station we need to take 2 reading at least FS & BS, and for each station we need to deduction the error (because its cumulative error). However, it's very small error and it remains always under tolerance.

Please give an explanation.

Please explain.

Someone Please explain clearly.

Explain it.

Please explain this.

Anyone explain the solution clearly.