.. _glossary:

Glossary
========

.. glossary::

    Reference ellipsoid
        An ellipsoid with geometric and physical properties used to best
        approaximate a given planetary body (the Earth or others).
        See `Wikipedia <https://en.wikipedia.org/wiki/Reference_ellipsoid>`__.

    Geocentric gravitational constant
        The multiplication of the total mass of a :term:`reference ellipsoid`
        and the `gravitational constant
        <https://en.wikipedia.org/wiki/Gravitational_constant>`__. Often
        represented as :math:`GM`.

    Normal gravity
        The magnitude of the gradient of the :term:`gravity potential` of a
        :term:`reference ellipsoid`.

    Gravity potential
        The combined gravitational and centrifugal potential
        :math:`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]_:
        :math:`\delta g(\lambda, \phi, h) = \|\vec{g}(\lambda, \phi, h)\| - \|\vec{\gamma}(\lambda, \phi, h)\|`