Civil Engineering Reference
In-Depth Information
Surveyors use the mathematical concept of Closure as an indication of the
correctness of a boundary description.
The concept of a closure is relatively straightforward and may be illustrated by
a simple example. Imagine that Fig.
4.14
is a small rectangular garden with a
fence running around its perimeter. There is a break in the fence so the gardener
can enter and exit the garden. The break is shown in the bottom left corner of the
image. Let's assume that you mentioned the garden to a friend who wants to create
a similarly sized garden on her property. She lives out of town so she asks if you
know of someone who could measure the garden for her and send her a written
note with the dimensions. You ask the gardener to do it and he takes a measuring
tape and begins measuring at the point labeled
Point of Beginning
. He contin-
ues to measure along the fence in the direction shown by the arrows and stops
at the point labeled “End Point”. If you add up the lengths of the 4 sides that he
measured, they will not give the actual size of the garden, because he neglected to
measure across the two foot gap in the lower left corner of the garden. In survey-
ing, the omission in his measurements would be called an
Error of Closure
. In
our example, the perimeter of the garden would actually be 360 feet, but he only
measured 358 feet. The measurements therefore have an error of 2 feet.
Fig. 4.14
Garden Fence error of closure
