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

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

Answer: (C)

Triangle closure is about how well the measured interior angles around a triangle of control points add up to 180 degrees. Because observations have errors, the sum often deviates a little, and that deviation is expressed in arcseconds as the triangle misclosure. For a third-order, class II geodetic control network, this misclosure is allowed to be up to ten arcseconds per triangle. This threshold strikes a practical balance: it accommodates typical observational precision while keeping the network consistent enough for reliable coordinates. Making the limit much tighter would push you toward higher-order control or require much more effort, whereas ten arcseconds provides a reasonable tolerance for this class of network. Therefore, the maximum allowed triangle closure is ten arcseconds.