What is a benchmark in surveying?

A benchmark in surveying is defined as a monument of known vertical position. This means that it provides a reference point that has a precise and established elevation above a specific datum, typically sea level. These benchmarks are critical in surveying and engineering as they allow for accurate elevation measurements and help ensure consistency across various surveys and construction projects.

Benchmarks are physically marked by monuments, which can include brass disks, concrete markers, or other durable materials. Surveyors use these reference points to determine the elevation of other points, making them essential in establishing and verifying topographic data, design elevations in construction, and for floodplain studies.

In contrast to the other options, a temporary point of measurement is typically a less permanent setup used for specific tasks that do not require long-term accuracy. While GPS signals provide positioning data, they do not establish a physical elevation reference like a benchmark. Lastly, measurement techniques refer to the methods used in surveying, rather than the reference points themselves. Thus, a benchmark's role as a monument of known vertical position is fundamental to ensuring accuracy in various surveying applications.