Loop Closure Loop Closure Loops.
Many caves have passages that wind around in a circle and connect back to themselves.
When a survey connects back to itself, it called a loop. If a loop is surveyed perfectly, the survey should come back to the exact point at which it started. If the loop doesn't come back to the exact starting point it is called a closure error. Closure errors indicate that some or all of the survey measurements within a loop have errors. If the closure errors are large enough, the shape of the loop and the shape of the cave will be distorted by the errors.