What is the primary function of a levelling instrument in surveying?

The primary function of a levelling instrument in surveying is to determine height differences and establish a horizontal line. This is essential for various applications in civil engineering, construction, and topographical surveys. When conducting a levelling operation, the instrument allows surveyors to maintain a consistent and accurate horizontal plane from which vertical measurements can be taken.

By using the instrument, surveyors determine the elevation of different points relative to one another, which is critical for tasks such as ensuring proper drainage, aligning structures, and establishing foundations. The accuracy of the horizontal line provided by the levelling instrument ensures that all subsequent measurements are precise and reliable, forming the basis for effective surveying practices.

Other choices, while related to surveying, do not pertain specifically to the function of a levelling instrument. For instance, measuring angles pertains to the use of theodolites or total stations, calculating geographical coordinates involves GPS technologies, and evaluating soil density necessitates different equipment and techniques. Thus, the role of the levelling instrument is distinct and pivotal in the context of surveying.