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

• A. 0.8 arcseconds
• B. 1.0 arcseconds
• C. 1.2 arcseconds
• D. 1.5 arcseconds

Answer: (C)

Triangle closure is the residual you get when the measured angles around a triangle are summed and forced to close to 180 degrees; the deviation from perfect closure is expressed in arcseconds. For second-order, class I geodetic control, the standard is that the average triangle closure should not exceed about 1.2 arcseconds. This level keeps the network internally consistent enough to produce reliable coordinates when the measurements are adjusted, balancing the inherent angular measurement errors with the precision required for high-quality control. Tighter limits like 0.8 or 1.0 arcseconds are more demanding and harder to meet across all triangles, while a limit of 1.5 arcseconds would be looser than the accepted standard for this class.