One World Three-Wire Differential Leveling

Three-wire checks, stadia distances, closure adjustment, and order classification

❓ How to Use This App

Enter the level run

  1. Enter the project and crew if desired.
  2. Enter the Starting BM Elevation. Enter the Known Closing Elevation when you want a closure check and adjustment.
  3. Select feet or meters, confirm the stadia constant, set the wire-check tolerance, and choose the target order/class.
  4. For each setup, enter the upper, middle, and lower wire readings for the backsight and foresight. Use Add Row for additional setups or turning points.
  5. Press Calculate at any time. The app also recalculates as values are edited.

Review the results

  • Wire Error checks the middle reading against the average of the upper and lower readings.
  • Distance is computed from the upper-minus-lower stadia interval times the stadia constant.
  • The summary shows computed closing elevation, misclosure, BS/FS distance balance, allowable misclosure, and closure status.
  • When a known closing elevation is supplied, the app distributes the closure correction by cumulative distance and reports adjusted elevations.
  • Export CSV saves the level-run inputs and calculated results. Load Example fills in a sample run for practice.

Example workflow

Start on a known benchmark, enter the three-wire backsight, then enter the three-wire foresight to the first turning point. Continue with the next backsight/foresight sequence until the run closes on a known benchmark. Enter that known closing elevation and review the misclosure and classification.

Important: The order/class result is based on closure only. Passing the closure tolerance by itself does not certify that the leveling run meets a formal geodetic order; equipment, sight lengths, balance, procedures, and the governing specification still matter.
Wire error = Middle − (Upper + Lower) ÷ 2. Stadia distance = (Upper − Lower) × stadia constant. Order classification below is based on closure only. Formal order also depends on equipment, sight-length limits, balance, observation procedures, and the governing agency specification.
#PointBacksightForesightCalculatedRemarksDelete
UpperMiddleLowerWire ErrorDistanceStatus UpperMiddleLowerWire ErrorDistanceStatus HIUnadjusted Elev.Segment DistanceCumulative DistanceCorrectionAdjusted Elev.BS−FS

Level Run Summary

Sum BS Middle
0.0000
Sum FS Middle
0.0000
Computed Closing Elevation
—
Known Closing Elevation
—
Misclosure
—
Total BS Distance
0.000
Total FS Distance
0.000
Total Run Distance
0.000
BS/FS Distance Difference
0.000
Allowable Misclosure
—
Closure Status
Enter readings
Wire Check Status
Enter readings
Observed Closure Constant
—
Closure-Based Classification
—

Classification Reference

Order / ClassMetric toleranceEquivalent feet tolerance
First Order, Class I3 mm√km0.0125 ft√mi
First Order, Class II4 mm√km0.0167 ft√mi
Second Order, Class I6 mm√km0.0250 ft√mi
Second Order, Class II8 mm√km0.0333 ft√mi
Third Order12 mm√km0.0500 ft√mi
The app reports the highest closure category achieved. Passing closure alone does not certify a formal geodetic order.