What defines a Benchmark (BM) in surveying?

A Benchmark (BM) in surveying is defined as a permanent point of known elevation established by precise leveling. This definition captures the essence of what a benchmark represents in the field of surveying. Benchmarks are crucial because they provide a reliable reference for future survey work, allowing surveyors to ensure consistent and accurate measurements over time.

Benchmarks are typically marked with a durable monument or marker to withstand environmental conditions and are strategically placed to be used as reference points in various surveying tasks. By having a recognized elevation at a specific point, surveyors can relate other elevations and establish terrains consistently across a specified area.

The other choices reflect various concepts in surveying but do not accurately describe a benchmark. A temporary marker for orientation does not have the permanence or the precise elevation information associated with a benchmark. A digital measurement of land elevation implies a technology or method rather than a physical reference point. Lastly, while a reference point for locating new construction may utilize benchmarks, it is not the defining characteristic of what a benchmark is. Thus, the distinction of benchmarks as established points of known elevation is crucial for their role in the practices of surveying.