In second-order, class I geodetic control, the maximum triangle closure should not exceed how many arcseconds?

• A. 3 arcseconds
• B. 5 arcseconds
• C. 1 arcsecond
• D. 10 arcseconds

Answer: (A)

Triangle closure error in a second-order, Class I geodetic network measures how consistent the angular observations are around a triangle. For the highest-precision networks, the allowed misclosure is kept very small to maintain overall accuracy. Specifically, the sum of the three measured interior angles should be 180 degrees within a tolerance of 3 arcseconds. In other words, the measured angles should add up to 180° ± 3", and if the closure exceeds this limit, the observations must be rechecked or adjusted to keep the network trustworthy.

Why this value fits: arcseconds are tiny units of angle, and 3 arcseconds corresponds to a highly stringent check on angular consistency without being impractically tight for field work. A misclosure of 1 arcsecond would be extremely strict for second-order Class I, while 5 or 10 arcseconds would be too large to meet the intended precision of such networks.