What is the term for the difference between vertical positioning on a geoid versus a spheroid?

The term that describes the difference between vertical positioning on a geoid and a spheroid is referred to as the deviation of the vertical. In geodesy, the geoid is a hypothetical surface representing mean sea level across the globe, while a spheroid is a mathematically defined surface used to approximate the shape of the Earth.

When surveying or mapping, the vertical positioning can differ between these two surfaces due to factors such as gravitational variations and the density of Earth's materials. This difference is crucial for precise measurements, as it impacts both elevation readings and the accuracy of geographical data. The deviation of the vertical represents this variation and is important in applications such as land surveying, navigation, and geophysical studies, ensuring that professionals in these fields can make informed and accurate decisions based on relative vertical positions.

The other options do not accurately encapsulate this specific difference; they may refer to related concepts but do not precisely define the distinction between the geoid and spheroid used in practical surveying scenarios.