In second order, class II geodetic control, the average triangle closure should not exceed how many arcseconds?

• A. 1.0 arcseconds
• B. 2.0 arcseconds
• C. 2.5 arcseconds
• D. 3.0 arcseconds

Answer: (D)

In a second-order, class II geodetic control network, triangle closure is a measure of how well the measured angles and sides form a closed geometric loop. Because observations have finite precision and possible biases, the sum of angles in a triangle or the loop of distances won’t be perfect, so there is a small misclosure that serves as a quality check for the network. The average triangle closure, expressed in arcseconds, captures how much these closures deviate on average across all triangles in the network.

For this level of network, a tolerance of about 3 arcseconds is the standard target. This limit reflects a balance: it’s tight enough to ensure reliable precision after the network is adjusted, but not so strict as to be impractical given typical field conditions and instrument limits for second-order work. If the average misclosure approaches or exceeds this level, it signals that revisiting observations or reweighting/adjusting the data is warranted to restore internal consistency. Smaller tolerances would be more appropriate for higher-order networks, while larger tolerances would undermine the network’s reliability.