Definition

The classifying of TRIAN­GULA­TIONS into first-order, second-order, and third-order triangulation, according to the ERROR OF CLOSURE OF TRIANGLES. In first-order work, the average closure is not in excess of 1 SECOND; in second order work, it does not exceed 3 SECONDS; and in third-order work, it does not exceed 5 SECONDS. For the basic first-order work, the computed length through the NETWORK must agree with the measured BASE within 1 part in 50 000, as a minimum, and average about 1 in 75 000, or bet­ter.