What does Geoid Height represent?

Geoid height represents the difference in height between the geoid and the reference ellipsoid used in geodetic measurements. The geoid is a model of Earth's mean sea level and gravitational field, providing a surface that is more closely aligned with the physical ocean surface. The ellipsoid is a mathematical model of the Earth's shape, which simplistically represents the Earth as a smooth, continuous surface.

When measuring positions or heights on Earth, surveyors and geodesists often need to understand how the geoid and ellipsoid relate to one another. The geoid height indicates whether a specific point on Earth is above or below the ellipsoidal surface. A positive geoid height means the geoid is above the ellipsoid, suggesting that actual ground elevation is higher than the theoretical representation of that point’s height as determined by the ellipsoid. Understanding this relationship is essential for accurate surveying, mapping, and navigation.

The other options, while related to height and positioning, do not encapsulate the specific definition of geoid height. Total height above sea level describes a different concept and measurement focus, while land elevation specifically ties into surface measurements without addressing the ellipsoidal reference. Lastly, referring to a standard reference for coordinates does not accurately capture the specific height