Height Anomaly

The height anomaly (usually denoted by ζ) is the difference between the ellipsoidal height of a point and its normal height. It represents the separation between the reference ellipsoid and the quasigeoid, analogous to the geoid undulation in classical geoid theory.

In geodesy, the height anomaly is a key quantity in Molodensky theory and modern height system realization. It allows the transformation of GNSS-derived ellipsoidal heights into physically meaningful normal heights without requiring knowledge of the Earth’s internal mass distribution. Accurate determination of height anomalies through gravity field modeling and satellite gravimetry is essential for consistent vertical reference systems and precise height determination.