Erdpotentialen

Erdpotentialen is a term used in geodesy and geophysics to denote the Earth's geopotential field—the potential energy per unit mass associated with the planet's gravity field, including the effect of rotation. It provides a single-valued scalar field in which the level surfaces are equipotential surfaces; moving along an equipotential surface would require no work against gravity. The geopotential is central to describing how gravity varies across the globe and to defining height systems.

The geopotential at a location is commonly written as W = Φ + Φc, where Φ is the gravitational potential due to Earth's mass distribution and Φc is the centrifugal potential produced by rotation. The gravity vector g is the gradient of W (g = ∇W). An important equipotential surface is the geoid, which roughly coincides with mean sea level and serves as the reference surface for heights.

Measurement and modeling: The Earth's geopotential is represented by expansions in spherical harmonics, with high-degree coefficients obtained from satellite missions such as GOCE and GRACE, supplemented by terrestrial gravimetry and altimetry. Modern models (for example, EGM2008 and successors) provide global maps of W and the gravity field, revealing features from mountains to ocean trenches as gravity anomalies in W.

Applications: Knowledge of Erdpotentialen underpins vertical datums, precise height measurements, and navigation; it is essential for satellite orbit determination, oceanography, geophysical interpretation of crustal structure, and mapping. The geopotential also informs studies of sea-level rise and Earth's interior dynamics.

See also: geoid, gravity field, vertical datum, gravity anomaly, geopotential height.