What is the primary purpose of using a datum in surveying?

The primary purpose of using a datum in surveying is to mark elevation. A datum provides a reference point or a base surface from which vertical measurements are taken. This is crucial for determining the height of structures, establishing grading for drainage, and understanding terrain variations. In the context of surveying, a datum typically refers to sea level or another established level that serves as a starting point for measuring elevation across the landscape. By having a consistent reference, surveyors can ensure that elevations are accurate and comparable across different locations, which is essential for construction, land development, and various engineering projects. This systematic approach helps in creating reliable maps and plans that reflect the true vertical aspects of the land.