What is defined as the permanent point of known elevation?

The term "benchmark" refers to a permanent point of known elevation, used commonly in surveying and construction. Benchmarks are typically made of durable materials and are marked on a physical object, such as a metal disk set in concrete, to withstand geological changes and ensure longevity. These points serve as crucial reference locations for measuring height and elevation in various projects. By using benchmarks, professionals can accurately establish elevations related to the surrounding terrain or structures, which is essential in ensuring accurate construction and topographical mapping.

While the other options have significance in surveying and construction, they do not specifically refer to a permanent point of known elevation. For example, a reference point may indicate a location from which measurements are taken but does not necessarily carry the defined elevation status of a benchmark. A datum is a base level for measurements but isn’t itself a physical point. An elevation stake might mark a temporary height on a job site, but it does not have the permanence and status associated with a benchmark.