For a closed traverse, you should attain a RATIO OF LINEAR ERROR OF CLOSURE that corresponds to the order of precision prescribed or implied for the traverse. The ratio of linear error of closure is a fraction in which the numerator is the linear error of closure and the denominator is the total length of the traverse.

To understand the concept of linear error of closure, you should study the closed traverse shown in figure 13-27. Beginning at station C, this traverse runs N30E300 ft, thence S30E300 ft; thence S90W 300 ft. The end of the closing traverse, BC, lies exactly on the point of beginning, C. This indicates that all angles were turned and all distances chained with perfect accuracy, resulting in perfect closure, or an error of closure of zero feet.

However, in reality, perfect accuracy in measurement seldom occurs. In actual practice,

Table 13-2.-Triangulation Order of Precision

Figure 13-27.-An example of a closed traverse with a perfect (zero-error) closure.

the closing traverse line, BC, shown in figure 13-27, is likely to be some distance from the starting point, C. If this should happen, and, say, the total accumulated linear distance measured along the traverse lines is 900.09 ft, the ratio of error of closure then is .09/900 or 1/10,000. This resulting ratio is equivalent to the precision prescribed for second order work.