# Glossary

- Aliasing
spurious tidal frequency appearing in an analysis due to inadequate temporal sampling

- Amplitude
one half of the range of a tidal constituent

- Anomaly
angular distance between the perihelion and the position of a celestial body

- Apogee
point of an orbit where a celestial body is furthest to Earth

see Perigee

- Aphelion
point of an orbit where a celestial body is furthest from the sun

see Perihelion

- Ascending Node
point of an orbit where a celestial body intersects the ecliptic, and the latitude coordinate is increasing

- Barycenter
center of mass of a system of bodies

- Body Tide
see Solid Earth Tide

- Chandler Wobble
small, semi-periodic deviations in the motion of the pole of rotation

- Constituent
- Declination
angular distance of an astronomical body north or south of the celestial equator

- Descending Node
point of an orbit where a celestial body intersects the ecliptic, and the latitude coordinate is decreasing

- Diurnal Tide
tidal oscillations with a near-daily period

- Ecliptic
plane of the orbit of the Earth around the sun

- Ephemeris
table of positions and velocities of a celestial body at given instances in time

- Ephemerides
plural of Ephemeris

- Epoch
fixed point in time used as a reference value

- Equilibrium Tide
hypothetical tide produced solely by lunisolar gravitational forces under equilibrium theory

- Frequency
number of cycles in a unit time

- Geoid
equipotential surface coinciding with the ocean surface in the absence of astronomical or dynamical effects

- Harmonic Analysis
mathematical process by which the tides are separated into Harmonic Constituents

- Harmonic Constants
amplitude and phase of the Harmonic Constituents

- Harmonic Constituents
harmonic elements of the tide-producing force corresponding with a periodic change of relative position of the Earth, Sun and Moon

- Harmonic Prediction
Method of estimating tidal elevations and currents through a combination of the Harmonic Constituents

- Load Tide
elastic deformation of the solid Earth due to ocean and atmospheric tides

- Long Period Tide
tidal oscillations with periods much greater than one day

- Love and Shida Numbers
dimensionless parameters relating the vertical (h), horizontal (l) and gravitational (k) elastic responses to tidal loading

- Mean Tide
model with both direct and indirect permanent tidal effects retained

- Nodal Corrections
adjustments to the amplitudes and phases of harmonic constituents to allow for periodic modulations

- Nutation
short-period oscillations in the motion of the pole of rotation

- Obliquity
angle between the equatorial and orbital planes

- Ocean Tide
periodic movement in the level of sea surface due to gravitational and rotational forces

- Perigee
point of an orbit where a celestial body is closest to Earth

see Apogee

- Perihelion
point of an orbit where a celestial body is closest to the sun

see Aphelion

- Period
time it takes to make one complete revolution

- Permanent Tide
permanent deformation of the Earth caused by the presence of the Sun and the Moon

- Pole Tide
apparent tide due to variations in the Earth’s figure axis about its mean

- Semi-diurnal Tide
tidal oscillations with an approximate half-day period

- Solid Earth Tide
deformation of the solid Earth due to gravitational forces

- Tidal Current
horizontal movement of water due to periodic forces

- Tidal Species
classification of tidal constituents based on period

see Semi-diurnal Tide, Diurnal Tide, and Long Period Tide

- Tidal Stream
see Tidal Current

- Tide-Free
model with direct and indirect permanent tidal effects removed

- Vertical Datum
reference coordinate surface used for vertical positions

- Zero Tide
model with permanent direct tidal effects removed, but indirect loading effects retained