Closure Ratio Classifier
Compute the closure ratio (1:N) of a traverse or parcel from linear misclosure and perimeter, and classify by geodetic accuracy order.
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About closure ratio and accuracy classification
The closure ratio expresses survey accuracy as a ratio: 1:10,000 means 1 meter of error for every 10 kilometers traversed. National geodetic standards use this ratio to classify surveys into orders. The United States Federal Geodetic Control Subcommittee (FGCS) defines five orders from first-order (1:100,000) to below-standard. This tool computes the ratio and assigns the classification.
Different projects require different orders. Cadastral/boundary work typically requires second-order Class II or better. Engineering traverses usually need third-order Class I (1:10,000). National control surveys demand first-order accuracy. Always check local regulations for the minimum required class.
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Practical use cases
Classifying a completed traverse before submitting to a client or regulatory body.
Deciding whether to accept fieldwork or re-observe stations showing poor closure.
Comparing multiple traverses on the same project to identify problematic sections.
Quick quality gate in field notes before returning from a survey site.
Frequently asked questions
What does "first-order" mean?
The most accurate classification in the FGCS standards: 1:100,000 or better. Used for national geodetic control and high-precision engineering.
Can a survey be better than 1:100,000?
Yes — modern GNSS networks routinely achieve 1:1,000,000 or better. First-order is simply the minimum for that class; real surveys often exceed it.
What if my misclosure is zero?
A closure of exactly 0 is suspicious — it may indicate numerical truncation or artificial data. Real fieldwork always has some residual.
How do these classes compare to European standards?
European countries use similar but varying standards. Germany: "Amtliche Vermessung" has comparable classes. UK Ordnance Survey uses different criteria for control surveys.
Related tools
Compute misclosure from individual courses using our parcel bearing calculator, or use traverse closure for full analysis.