What is the reference point used by surveyors for determining elevations called?

The correct answer is "Datum." In surveying, a datum is a reference level or baseline used to measure elevations. It represents a standardized point from which all heights or depths in a particular area are calculated. This ensures consistency and accuracy across various surveys and measurements, as different locations can have distinct topographical features, so a common reference point is essential for establishing relative elevations.

Benchmarks, while related to datum, are specific physical markers that denote a known elevation at that point, often used to create a network of horizontal control points over a wide area. Elevation marks are similar but may refer more broadly to any estimated height above a defined baseline without the specificity of a datum. Survey reference is a more general term referring to any techniques or practices used in surveying rather than to a specific point of elevation reference. Thus, "Datum" is the precise term used to denote the standard reference point for establishing elevation.