Check lines (or proof lines) in Chain Surveying are essentially required

🔊 Understanding Check Lines

In chain surveying, the area is divided into a framework of triangles. A check line, also known as a proof line, is a line measured in the field that joins two established points within this framework, such as the apex of a triangle to a point on its base.

The primary and essential purpose of a check line is to verify the accuracy of both the fieldwork and the subsequent plotting. The length measured on the ground should exactly match the length scaled on the plotted map. Any discrepancy indicates an error in measurement or plotting.

🔬 Detailed Analysis of the Options

• A. to plot the chain lines: This is incorrect. The main survey lines (like the base line) and station points are used to create the initial plot of the framework.
• B. to plot the offsets: This is incorrect. Offsets are short measurements taken to locate details relative to a chain line. While important, they are not plotted using check lines. Tie lines are often used to avoid long offsets.
• C. to indicate the accuracy of the survey work: This is the correct answer. By comparing the field measurement of the check line to its scaled length on the drawing, the surveyor can confirm the precision of the triangulation and plotting.
• D. to increase the out-turn: This is incorrect. Measuring check lines is an extra step that takes time; it's a quality control measure, not a method to speed up the work or increase output.

📊 Summary of Lines in Chain Surveying