# Glossary#

Reference ellipsoid#

An ellipsoid with geometric and physical properties used to best approaximate a given planetary body (the Earth or others). See Wikipedia.

Geocentric gravitational constant#

The multiplication of the total mass of a reference ellipsoid and the gravitational constant. Often represented as $$GM$$.

Normal gravity#

The magnitude of the gradient of the gravity potential of a reference ellipsoid.

Gravity potential#

The combined gravitational and centrifugal potential $$U = V + \Phi$$ [HofmannWellenhofMoritz2006].

Gravity disturbance#

The gravity disturbance is the difference between the magnitude of observed gravity and the magnitude of normal gravity evaluated at the same point [HofmannWellenhofMoritz2006]: $$\delta g(\lambda, \phi, h) = \|\vec{g}(\lambda, \phi, h)\| - \|\vec{\gamma}(\lambda, \phi, h)\|$$