Levelling reduction calculator — rise and fall / collimation
Free, no sign-in. Nothing you type is stored or sent anywhere — it's all worked out in your browser.
Paste spreadsheet rows
Not legal or tax advice — check your contract. Your contract terms and the facts of your job can change the answer.
How this works
Start with a BS only. Use IS for intermediate points, FS for the end of a setup, and both FS and BS on the same change-point row. Finish with a FS only. All readings and levels are metres.
Rise and fall compares successive sights within each setup. HPC is RL plus BS; forward RLs are HPC minus IS or FS. Both give the same unadjusted levels.
R&F check: ΣBS − ΣFS = ΣRise − ΣFall = last RL − first RL. HPC also checks ΣRL excluding the first against the sum of the original HPC for every forward sight minus ΣIS minus ΣFS.
Misclosure is observed closing RL minus known closing RL. Choose a fixed mm tolerance, k√(km), or k√(setups). Equal-per-setup correction accumulates at completed setups; intermediate sights receive the correction accumulated before their setup.
FAQs
How do I enter a change point?
Use FS from the previous setup and BS from the new setup on the same row. Leave IS blank.
Can I paste a spreadsheet?
Yes. Paste BS, IS, FS and remarks as tab-separated rows, with blank cells for unused sights.
Does adjustment fix bad observations?
No. Check arithmetic, field notes and tolerances before adjusting. A failed tolerance may require re-levelling.
Is there a default survey tolerance?
The 10 mm starting figure is editable, not a prescribed standard. Enter the tolerance required for your work.
Civvio works this out automatically from your contract and site records.
Upload the contract and keep your diary, and Civvio flags the dates, notices and money at risk on every job — for you to review before anything is sent.
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