Levelling field book and level run adjustment online

Copy the staff readings from your field book: the calculator computes height differences, checks every set-up, performs the page check, finds the misclosure of the run, compares it with the tolerance, adjusts the differences and computes reduced levels. A profile is plotted at once.

StaffsStart benchmark level, m

Readings per set-up, mm

№	Backsight point	Foresight point	BS black	BS red	FS black	FS red	L, m
1
2
3
4

You can paste a block from Excel or Word: click a cell and press Ctrl+V.

One row per set-up. a — backsight, b — foresight, in millimetres (1842) or metres (1.842). L — set-up length in metres: corrections are proportional to L if given, equal otherwise.

Misclosure toleranceBlack/red difference at a set-up

Calculate

Differential levelling

A level gives a horizontal line of sight; the height difference between two points is h = a − b, backsight minus foresight.

Set-up and page checks

With double-faced staffs the black and red differences must agree within ±5 mm (allowing for a ±100 mm zero offset between staffs). Page check: Σa − Σb = Σh.

Misclosure and adjustment

Closed loop: f = Σh; between benchmarks f = Σh − (H end − H start). Technical tolerance 50 mm·√L (L in km). Corrections v = −f·L / ΣL, levels H(i+1) = H(i) + h + v.

Example

Loop Rp1 → X1 → X2 → X3 → Rp1, H(Rp1) = 125.430 m: misclosure +4 mm, tolerance ±32 mm, −1 mm per set-up; X1 = 126.117, X2 = 125.206, X3 = 124.650 m.

FAQ

How is the misclosure of a level run computed?

Sum the mean height differences; for a loop that is the misclosure, between benchmarks subtract the known level difference. Technical tolerance: 50 mm·√L.

What is the page check?

Sum of backsights minus sum of foresights must equal the sum of height differences.

Why do red differences differ by 100 mm?

The red faces of a staff pair start at different zero offsets, typically 4687 and 4787 mm; the calculator removes this ±100 mm automatically.

How is the misclosure distributed?

With opposite sign, in proportion to set-up lengths (or equally), rounded to millimetres so the corrections sum to −f exactly.

What black/red difference is acceptable?

Up to 5 mm for technical levelling; otherwise the set-up is repeated.