A datum point in construction is a known reference point from which additional measurements or analyses can be conducted. The point can be determined by the completed floor level, an existing structure, or a benchmark.
In the context of a benchmark, a datum point is a position above sea level. A datum can be derived from a network of benchmarks. These are used to build new homes, roadways, and stone pillars. A datum point can also be used in modelling geometry, where multiple points can be added to the model.