geoid
/ˈdʒiːɔɪd/
noun
- The shape that the surface of the Earth's oceans would take if they were not disturbed by tides, winds, or currents, used as a model for measuring the Earth's true shape.
- The geoid is not a perfect sphere because gravity varies across the planet.
- Scientists use the geoid to calculate precise elevations on land.
- GPS devices rely on the geoid model to give accurate altitude readings.