- Theoretical surface (non-smooth) resulting from oceans allowed to settle under influence of gravity only (w/o tidal or atmospheric forces)
- Surface approximately equal to mean sea level (MSL) and calculated from gravity data using a geoid model
- Varies over time due to slight changes in Earth’s gravity, therefore geoid models are regularly updated
- Used to convert from ellipsoidal height to orthometric height
Geoid height
- Vertical distance between reference geoid and ellipsoid
Examples
- EGM96, EGM2008 (global models)
- GEOID12B, GEOID18 (USA-specific models)