The geoid is defined as the average level of the sea, which is thought of as extended through the continents.
In physical geodesy, gravimetric data are used for the determination of the geoid and components of deflections of the vertical.
The reduction of triangulation base lines from the geoid to the reference ellipsoid.
The west-European and the Russo-Scandinavian meridians indicate another anomaly of the geoid.
It's geoid teah is this; aw've monny a time ta'en a gooid swig aght o' that teah-pot before to-day.
The hypothetical surface of the Earth that coincides everywhere with mean sea level and is perpendicular, at every point, to the direction of gravity. The geoid is used as a reference surface for astronomical measurements and for the accurate measurement of elevations on the Earth's surface.