What is a benchmark in the context of surveying?

A benchmark in surveying is defined as a reference point of known elevation that serves as a measurement standard for other elevations in the vicinity. It is often a physical marker placed in a permanent location, such as a metal disc or a brass plate, which indicates its precise height relative to a standardized datum, usually sea level. Surveyors use benchmarks extensively to ensure consistent and accurate measurements for various applications, including construction projects, land development, and mapping.

The use of benchmarks allows surveyors to create a reliable framework for determining the topography of an area, making it essential for establishing features like grading plans, drainage systems, and structural foundations. Benchmarks can be utilized in both horizontal and vertical control, supporting planning and design efforts by referencing back to known elevations established in the field. This is crucial for maintaining elevation consistency across different surveying projects.