Missing Line & Measurement Solver
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Known measurements
Enter every measurement except the unknown one — mix bearing/distance and ΔE/ΔN as you like. The missing measurement is the vector that closes the figure. Runs in your browser.
Missing measurement
How to use this calculator
- Enter every known measurement, leaving out the unknown one. Each leg can be a bearing + distance OR ΔE / ΔN components — mix the two freely.
- Pick a bearing format as needed.
- Read the missing measurement in BOTH forms: bearing + distance and ΔE / ΔN.
How it works
For a closed figure the eastings (ΔE) and the northings (ΔN) each sum to zero. A bearing+distance leg is first resolved into ΔE = distance·sin(bearing) and ΔN = distance·cos(bearing); adding up all the known legs leaves a residual, and the missing measurement is exactly the vector that cancels it — ΔE = −ΣΔE, ΔN = −ΣΔN, bearing = atan2(ΔE, ΔN), distance = √(ΔE² + ΔN²).
It's the same maths as a misclose, used deliberately to recover one unmeasured line, distance pair or coordinate difference.
Worked example
Legs N100, E100, S100. The three legs leave a 100 m gap to the west, so the missing measurement is bearing 270° for 100 m, or ΔE −100 m / ΔN 0 m.
Frequently asked questions
Can I mix bearing/distance and ΔE/ΔN legs?
Yes. Each row has its own type — enter whichever you have for that leg. They're all converted to ΔE/ΔN before summing.
Can I solve two missing measurements?
No — this recovers a single unknown vector. With two unknowns the figure is under-determined; you need another observation or assumption.
Is this official course material?
No. It is free study support mapped to surveying course levels — not official North Metropolitan TAFE content or advice. Always follow your lecturer and the official assessment brief, and check your own working.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.