.. _glossary:
Glossary
========
.. glossary::
Co-located grids
One or more grids that have grid points are at exactly the same locations.
This property is important when performing operations like adding and
subtracting grid values since they must be located at the same
geographical locations.
Geocentric gravitational constant
The multiplication of the total mass of a :term:`reference ellipsoid`
and the `gravitational constant
`__. Often
represented as :math:`GM`.
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]_:
:math:`\delta g(\lambda, \phi, h) = \|\vec{g}(\lambda, \phi, h)\| - \|\vec{\gamma}(\lambda, \phi, h)\|`
Gravity potential
The combined gravitational and centrifugal potential
:math:`U = V + \Phi` [HofmannWellenhofMoritz2006]_.
Normal gravity
The magnitude of the gradient of the :term:`gravity potential` of a
:term:`reference ellipsoid`.
Reference ellipsoid
An ellipsoid with geometric and physical properties used to best
approximate a given planetary body (the Earth or others).
See `Wikipedia `__.