Which reference is used for measuring elevations of surfaces and features on Earth?

The appropriate reference for measuring elevations of surfaces and features on Earth is a vertical datum. A vertical datum serves as a baseline or reference level from which elevations and depths are calculated. It provides the framework for determining the height of features above or below this reference surface, allowing for a consistent way to communicate and manage elevation data.

Examples of vertical datums include the North American Vertical Datum of 1988 (NAVD88) and the National Geodetic Vertical Datum of 1929 (NGVD29). These datums determine how elevations are measured, ensuring that measurements are standardized across different regions and applications.

In contrast, a geodetic datum refers more broadly to a model that defines the shape of the Earth and serves as a reference point for positioning data, while a horizontal datum relates specifically to the geographic coordinates used for mapping on the Earth’s surface, typically dealing with latitude and longitude. The World Geodetic System, often referenced for global positioning and navigation, functions as a comprehensive geodetic datum but does not specifically address elevation measurements in the way a vertical datum does.