OrthometricHöhe

Orthometric height, often denoted as H, represents the height of a point above a reference geoid. Unlike geometric height, which is measured perpendicular to an ellipsoidal model of the Earth, orthometric height is the distance along the plumb line from the geoid to the point in question. This height is conceptually simpler for practical applications like engineering and hydrology because it represents the potential energy of the water at that point. It essentially measures the height that water would reach if it were free to flow from that point to sea level under gravity.

The geoid itself is an equipotential surface of the Earth's gravity field that approximates mean sea level. Because gravity is not uniform across the Earth, the geoid is an irregular, undulating surface. Calculating orthometric height typically involves first determining the geometric height (h) from an ellipsoid and then subtracting the geoid undulation (N) at that location. The formula is H = h - N. This process requires accurate geoid models and precise geometric height measurements, often derived from GPS or leveling surveys. Orthometric heights are crucial for establishing consistent vertical datums for mapping, surveying, and infrastructure projects.