Which of the following specifies a maximum triangle closure of 3 arcseconds for second-order geodetic control?

• A. Second-order, class I
• B. First-order
• C. Second-order, class II
• D. Third-order, class I

Answer: (A)

Triangle closure is the residual error that remains when a closed figure formed by triangulation is balanced; in practice, the measured directions and angles should loop back to the starting point, and any imbalance is quantified as an arcsecond value. Geodetic control networks are categorized by order and class, with tighter tolerances for higher accuracy. For second-order control, class I represents the stricter, more accurate subset, and the standard specifies a maximum triangle closure of 3 arcseconds for that case. Therefore, the option describing second-order control with the higher accuracy class fits the 3 arcsecond limit exactly. The other possibilities refer to different orders or to the less stringent second-order class II, which do not have this 3 arcsecond threshold.