What is meant by "Vertical Control" in surveying?

Vertical control refers to a system of reference points that provide precise elevation measurements throughout a surveying project. This is essential for ensuring the accuracy of height determinations, which can be critical for various engineering and construction applications, such as establishing grades for roads or determining water drainage patterns.

The use of precise elevations allows surveyors to relate their measurements to a known datum, which serves as a baseline for height comparisons. This is vital in areas where topography varies significantly, as it helps in creating accurate three-dimensional representations of land features. Elevation data is often critical for projects involving infrastructure, environmental studies, and land use planning, as it directly influences how a project will interact with the surrounding landscape.

In contrast, the other options pertain to different aspects of surveying. For instance, recording surface water flow relates more to hydrology than to vertical control, while creating flat maps is associated with horizontal control and cartography. Lastly, boundary surveys focus on defining property lines, which does not involve elevation but rather horizontal dimensions and legal perimeters. Therefore, the choice of a system of precise elevation reference points as the definition of vertical control is correct and reflects its key role in surveying practices.