What do benchmarks refer to in the context of land surveying?

Benchmarks in the context of land surveying refer to fixed reference points that have been established to aid in determining elevations and providing a baseline for various surveying activities. These benchmarks, often created and maintained by organizations like the U.S. Geological Survey, are critical for ensuring accuracy in surveying and mapping work. They help surveyors calculate differences in elevation and serve as reliable points for connecting with other surveying data.

The other options presented do not accurately capture the definition of benchmarks in land surveying. Measurements of soil quality pertain to environmental science or agriculture rather than surveying. Markers indicating land ownership changes relate more to property boundaries and titles rather than fixed elevation points. Points of interest for geographical studies may involve noteworthy locations but do not specifically address the standard reference points necessary for surveying purposes. Thus, the understanding of benchmarks as established fixed points is essential for the profession of land surveying.