What is the purpose of a benchmark in surveying?

The purpose of a benchmark in surveying is to provide a permanent reference mark for elevations. Benchmarks are critical for determining the height of land above a reference point, typically mean sea level. They are used extensively in topographic mapping, engineering projects, and construction to ensure that structures are built at the correct elevation and to facilitate accurate measurement of changes in elevation over time. Setting a benchmark allows surveyors to create a consistent elevation reference that can be used across large areas, ensuring uniformity in measurements.

While measuring land area, establishing legal descriptions, and defining property boundaries are also important aspects of surveying, they do not pertain specifically to the role of a benchmark in elevation measurement. Benchmarks focus primarily on vertical positioning rather than horizontal dimensions or legal boundaries.