_____ is one of the lines in a triangulation system whose length is also precisely measured and may be located at regular intervals or at the end of triangulation system.

• A. Base line
• B. Check base
• C. Observation line
• D. Triangulation line

Answer: (B)

In triangulation work, a line of known, very precise length is added as a check across the network to verify accuracy. This is the check base. It may be placed at regular intervals or at the ends of the triangulation system so you can compare the distance measured directly with the distance inferred from the angles and overall geometry. If the measured length matches what the triangulation calculations produce, the network’s scale and measurements are consistent; if not, it signals errors to identify and correct. This differs from the base line, which is the primary, initial segment used to start the network, and from general triangulation or observation lines, which are defined by the network layout and observations rather than as a dedicated precision-check length.