close

In surveying, a traverse closes when the sum of all measured distances and angles returns the surveyor to the starting point. A closed polygon means the vector sum of all legs equals zero: you walked north 100 meters, east 50, south 100, west 50, and ended where you began. This is the surveyor's built-in quality check. If your measurements do not close, you have made an error in distance, bearing, or both.

Closure is expressed as a ratio of error to perimeter. A closure of 1:5000 means your accumulated error across the entire traverse is one unit for every 5000 units measured. Most jurisdictions require 1:10000 or better for boundary surveys; engineering surveys often demand 1:5000 or tighter. A traverse that does not close at all has failed and must be remeasured or discarded.

Why closure matters in the field

Before computers, surveyors closed traverses by hand and adjusted coordinates proportionally across all legs. Modern software does this work instantly, but the principle remains: a closed traverse proves internal consistency and catches blunders before they contaminate the rest of the project. An open traverse, one that fails to close, reveals a distance was recorded wrong, an angle was misread, or a setup was skipped.

Closure is different from accuracy. A traverse can close perfectly and still be wrong if your instrument was miscalibrated or you misidentified the starting point. Closure confirms your measurement process was methodical; accuracy requires that your measurements match the real world. Both matter for any survey that will be used in legal or engineering decisions.