• Absolute reference: Galilean reference frame (without acceleration).
  • Admittance: the ocean's response, depending on the frequency, to the action of the generating force.
  • Age of the tide: time interval between the syzygy and the maximum range of tide that follows.
  • ALLENVI: Environmental alliance.
  • Altimetry: measurement of the height of water using spatial techniques.
  • Amphidromic points: points located at sea around which the tide wave appears to turn.
  • Amplitude: difference between the height of a high or low tide and the mean level. This term is often used in error to designate the range of tide.
  • Apparent time: true solar hour angle.
  • Argument number: method for designating the components of the tide, using a 6-figure number, making it possible to identify the astronomical parameters from which they are derived and deduce from them their period.
  • Ascending node: point at which the lunar orbit and the ecliptic intersect in the direction of movement of the Moon from the Southern to the Northern hemisphere.



  • Backrush current: current generated by the slope of the free surface, excluding the action of the tide.



  • CCI:  Chamber of Commerce and Industry.
  • CEA/LDG: Commissariat à l'Energie Atomique et aux Energies Alternatives / Laboratoire de Détection et de Géophysique (Atomic energy and alternative energy commission / Detection and geophysical laboratory).
  • CENALT: Centre national d'alerte aux tsunamis (national tsunami alert centre)
  • CETE: Centre d'études techniques de l'équipement (equipment technical study centre).
  • CETMEF: Centre d'Etudes Techniques Maritimes Et Fluviales (maritime and fluvial technical study centre
  • CG: Conseil Géneral (county council)
  • CGC: Commission de gestion de configuration (configuration management committee)
  • CGEDD: Conseil général de l'environnement et du développement durable (general council for the environment and sustainable development)
  • Chart datum: same as hydrographic datum.
  • CIL: Correspondant Informatique et Libertés (data protection coordinator).
  • CIMER: Comité interministériel de la mer (interministerial committee for the sea)
  • Civil time: mean time plus 12 hours.
  • CNES: Centre National d'Etudes Spatiales (national space study centre)
  • CNRS: Centre National de la Recherche Scientifique (national scientific research centre)
  • Coefficient: measurement of the amplitude of the tide expressed relative to the unit of height.
  • Concordance; species concordance: tidal analysis and prediction technique using the relations between the elements of a standard port and those of a secondary port.
  • Cotidal line: line on a chart passing through all the points at which high tide occurs at the same time.
  • CR: Conseil Régional (regional council)
  • CRATANEM: Centre régional d'alerte aux tsunamis pour l'Atlantique Nord-Est et la Méditerranée (Regional tsunami alert centre for the North East Atlantic and Mediterranean)
  • Current amplitude: maximum speed during a tidal cycle.
  • Current atlas: cartographic representation of the tidal current fields at various times.



  • Damping well: Device in a tidal observatory designed to flatten the area of water and reduce rapid movements due to waves and swell.
  • DDE: Direction Départementale de l'Equipement (county council infrastructure directorate)
  • DDEA 14 / SRAN: Direction Départementale de l'Equipement et de l'Agriculture du Calvados / Service Réglementation et activités nautiques (county council infrastructure and agricultural directorate for the Calvados department / Regulatory and nautical activities department)DDTM: Direction Départementale des Territoires et de la Mer (county council territorial and maritime department)
  • Declination: angle between the celestial body and the equatorial plane.
  • DéGéOM: Délégation générale de l'Outre-Mer (general delegation for overseas territories)
  • DGEC/ONERC: Direction générale de l'énergie et du climat / Observatoire national sur les effets du réchauffement climatique (general directorate for energy and climate / National observatory of the effects of global warming)
  • DGM: Direction générale de la météorologie (Madagascar) (general directorate for meteorology (Madagascar))
  • DGPR: Direction générale de la prévention des risques (general directorate for risk prevention)
  • Diurnal tide: one high water and one low water per day; the semi-diurnal components are negligible.
  • DMS: Demande de mise en service (commissioning request)
  • DMSOI: Direction de la Mer Sud Océan Indien (Directorate for the Sea – Southern Indian Ocean)
  • Doodson number: another name for an argument number.
  • DRE: Direction régionale de l'Equipement (regional infrastructure directorate)
  • DREAL - LR: Direction régionale de l'environnement, de l'aménagement et du logement - Languedoc-Roussillon (regional directorate for infrastructure, development and housing – Languedoc-Roussillon)
  • Drift current: current generated by the wind.
  • DSC: Direction de la Sécurité Civile (directorate of civil safety).



  • Ebb current or ebb: current accompanying the ebb tide.
  • Ebb: synonym of falling tide.
  • Ecliptic latitude: angle between the celestial body and the ecliptic plane.
  • Ecliptic longitude: angle between the orthogonal projection on the ecliptic of the direction of the celestial body and the direction of the vernal point.
  • Ecliptic: the Earth's orbit around the Sun or the Sun's apparent orbit viewed from the Earth.
  • Ellipsoid: mathematical surface defining a geodetic system based on the relative positions of points located on the Earth's surface.
  • Equation of time: difference between the mean time and the true time. Species: set of components whose frequencies are close to a given number of cycles per lunar day. we distinguish between species with long periods, diurnal and semi-diurnal species.
  • Equator: terrestrial great circle contained within the plane perpendicular to the polar axis.
  • Equinoctial point: intersection of the ecliptic plane and the equator.
  • Equinoctial spring tide: maximum amplitude of the semi-diurnal tide around the equinoxes.
  • Establishment of the port: time (true time) of high water on a day on which syzygy occurs at apparent noon.
  • EuroGOOS: European Global Ocean Observing System
  • Exceptional spring tide: semi-diurnal perigean equinoctial spring tide.
  • Extended argument number: Doodson number to which a 7th figure has been added, specifying whether the angular argument is associated with a positive or negative sine or cosine.



  • Falling tide: period during which the water level falls.
  • FAQ: Frequently Asked Questions (or Foire Aux Questions in French)
  • FFT: Fast Fourier Transform. Technique for representing a time signal in the spectral domain.
  • Fix sphere: representation system in which reference is made to celestial bodies by their direction on a sphere whose position is fixed with respect to the stars.
  • Flood current or flood: current accompanying the rising tide.
  • Flood: synonymous with rising tide.
  • Foreshore: Coastal strip between the levels achieved by the highest and lowest tides.



  • Generating force: resultant of the gravitational attractive force exerted by celestial bodies at a point on the Earth and the inertial driving force of a reference base associated with the Earth.
  • Generating potential: scalar magnitude from which the generating force is derived.
  • Geocentric zenith distance: zenith distance with respect to the centre of the earth.Historical data or metadata: Tide gauge data in non-digital format
  • Geodetic coefficient: element of the expression of the generating potential depending solely on the latitude.
  • Geographical coordinates: terrestrial latitude and longitude.
  • Geoid: equipotential surface of the Earth's gravitational field.
  • GLOSS: The Global Sea Level Observing System
  • GOES: Geostationary Operational Environmental Satellites
  • GPM: Grand Port Maritime (major maritime port)



  • Half tide: means of high and low waters.
  • Harmonic analysis: calculation of the harmonic constants of the tide.
  • Harmonic component: elementary tide wave, defined by its frequency, amplitude and phase.
  • Harmonic constant: the amplitude and situation of a harmonic component are harmonic constants of the said component.
  • HCR/DDPC-PF: Haut commissariat de la République de Polynésie française / Direction de la Défense et de la Protection Civile - Polynésie française (High commission of the Republic in French Polynesia / Directorate of defence and civil protection – French Polynesia)
  • HCR/DSC-NC: Haut commissariat de la République en Nouvelle-Calédonie / Direction de la Sécurité Civile - Nouvelle-Calédonie (High commission of the Republic in New Caledonia / Directorate of civil safety – New Caledonia)
  • High and low waters: extremes of the tide curve.
  • Hour angle: angle between the meridian half-plane of the position and the meridian half-plane of the celestial body, measured clockwise in the direction of the heavenly body.
  • Hydrographic datum: also called chart datum, common reference for nautical charts and tide tables for use by navigators.



  • IBI-ROOS: Ireland-Biscay-Iberia Regional Operational Oceanographic System
  • IDSC: Inspection de la défense et de la sécurité civile (Defence and civil safety inspectorate)
  • IFREMER: Institut Français de Recherche pour l'Exploitation de la MER (French research institute for the exploitation of the sea)
  • IGA: Inspection générale de l'administration (General admistration inspectorate)
  • IGF: Inspection générale des finances (General finance inspectorate)
  • IGN
  • IGN :  Institut national de l'information géographique et forestière ()
  • IIW: Institution interdépartementale des wateringues (Interdepartmental reclaimed land institution)
  • INPI: Institut national de la propriété industrielle (National institute for industrial property)
  • INSU: Institut National des Sciences de l'Univers (National institute for universal sciences)
  • Interaction component: Harmonic component generated by the non-linear effects of the ocean's response to the generating force.
  • IOC: Intergovernmental Oceanographic Commission
  • IPEV: Institut polaire français Paul Émile Victor (Paul Emile Victor French polar institute)
  • IPGP: Institut de physique du globe de Paris (Paris Earth physics institute)
  • IRD: Institut de Recherche pour le Développement (Research Institute for Development)
  • IRSN: Institut de Radioprotection et de Sûreté Nucléaire (Institute for radioprotection and nuclear safety)
  • ISDR: International Strategy for Disaster Reduction
  • ITRS: International Terrestrial Reference System.



  • JMA: Japan Meteorological Agency
  • JODC: Japanese Oceanographic Data Centre



  • Lagging tide: period in which the amplitude reduces.
  • Latitude: angle between the direction of the vertical of the position and the equatorial plane.
  • Least squares: calculation method making it possible to obtain an optimum estimate of a deterministic signal in the presence of noise.
  • Legendre polynomials: orthogonal polynomials. The generating potential is expressed in the form of a series of Legendre polynomials.
  • LEGOS: Laboratoire d'Études en Géophysique et Océanographie Spatiales (Space geophysics and oceanography studies laboratory).
  • Literal argument: argument number in which the figures have been replaced by letters.
  • Littoral circulation: resultant of the backrush current (gradient current) and the drift current near to the coast.
  • Longitude: angle between the meridian half-plane of the position and the origin meridian (the Greenwich meridian).
  • Low water: the lowest level reached by the sea during a tidal cycle.
  • Luminous probe: graduated tape, generally made from metal, equipped with a device indicating, by means of a light signal, when its end comes into contact with the surface of the water.
  • Lunar month: also known as the synodic revolution, it is the time interval between two full moons and two new moons.



  • Marigram: graphic showing variations of the sea level, in a single location, as a function of time.
  • MARIS: Marine Observations Service.
  • Mean anomaly: angle between the direction of the mean sun and that of the perihelion.
  • Mean high water lunitidal interval: mean interval between the time of high water and the Moon's meridian passage.
  • Mean level: result of a digital filtering of the heights observed tending to eliminate the sinusoidal components.
  • Mean longitude: ecliptic longitude of a celestial body or an element of its orbit. This designation is not really apposite (it is not the mean of the longitudes), but it is the term generally used.
  • Mean ocean surface: surface of the oceans determined by space altimetry.
  • Mean Sun: fictitious celestial body having the same apparent period of revolution as the true Sun, but with uniform motion. The mean time varies by 0 to 24 hours from the passage of the mean Sun through the upper meridian.
  • Mean time: uniform time scale defined by the mean Sun. By definition, a mean time day is 24 hours in length.
  • MEDDTL: Ministère de l'écologie, du développement durable, des transports et du logement (Ministry for ecology, sustainable development, transport and housing)
  • Meridian plane: plane containing the polar axis.
  • Meshing: Subdivision of an area into simple geometric elements with a view to carrying out mathematical modelling.
  • MESR: Ministère de l'enseignement supérieur et de la recherche (Ministry for higher education and research)
  • MIOMCTI: Ministère de l'intérieur, de l'outre-mer, des collectivités territoriales et de l'immigration (Ministry of the interior, overseas territories, territorial communities and immigration)
  • Mixed tide: sometimes two high waters and two low waters per day, at other times one high water and one low water per day; the diurnal components are dominant.



  • Nadir: point on the celestial sphere directly beneath the observer; opposite of zenith.
  • Neap tide: minimum tidal range.
  • NOAA: National Oceanic and Atmospheric Administration
  • Nodal correction: correction to be applied to the harmonic constants to take into account the variations in the elements of the lunar orbit.
  • Noise: component of the magnitude observed inaccessible to harmonic analysis.
  • NOOS: North West European shelf Operational Oceanographic System
  • NTC: National Tidal Centre
  • NUNIEAU: Digitization of water levels



  • Observatory: organization established in order to study phenomena, events, humans and their activities and elicit remarks and reflections concerning them.
  • OCA: Observatoire de la Côte d'Azur (Observatory of the Côte d'Azur)
  • OELR: Office de l'eau de La Réunion (Water office of La Reunion)
  • ONERC: Observatoire National sur les Effets du Réchauffment Climatique (National observatory of the effects of global warming)
  • OPECST: Office parlementaire d'évaluation des choix scientifiques et technologiques (Parliamentary office for the evaluation of scientific and technological choices)



  • Perigean spring tide: maximum amplitude of the tide around the passage of the Moon at its perigee.
  • Perigee: closest point of the orbit to a focus.
  • PNA: Ports Normands Associés (associated Norman ports).
  • Polar axis: the Earth's axis of rotation.
  • Polar distance: complement at 90° to the declination.
  • Portlet : un portlet est une application informatique que l'on trouve dans le portail REFMAR, qui sert de conteneur. C'est un objet qui affiche un bloc d'informations. Un portlet traite les requêtes d'une tâche ou d'un service donné et génère dynamiquement le contenu Web affiché à l'utilisateur. Les portlets permettent de fournir toutes sortes de services généralistes ou spécialisés. Par exemple, la page html d'un observatoire contient les portlets suivants : "Etat de la station", "Telechargements", "Recherche", "documentation", "Histoire de la station", "Feuille d'information", "Dernières données disponibles", "Carte de détail de la station", "Galerie d'images", "Journal de bord".
  • Priming: period during which the amplitude of the tide increases between neaps and springs.
  • Proctor's rule: geometric construction of the tide generating force
  • PSMSL: Permanent Service for Mean Sea Level



  • Quadrature : position of the Moon and Sun when their directions with respect to the Earth form a right angle (general term for the first and last quaters).



  • Radiational component: as opposed to gravitational components, these are components derived from the sun's radiational action.
  • RAM: Références altimétriques maritimes (hydrographic datums)
  • Range of tide: Difference in height between successive low and high waters.
  • Reduced heights: periodic magnitudes, resulting from an interpolation of heights observed for calculating reduced vectors.
  • Reduced vectors: complex numbers representing the component elements of a species (modulus and phase) at a given moment)
  • REFMAR: Réseaux de référence des observations marégraphiques (Tide gauge observation reference networks)
  • Response method: tidal analysis and prediction technique based on admittances.
  • Right ascension: angle between the meridian plane of the celestial body and the vernal point, measured anti-clockwise towards the celestial body.
  • Rising tide: time interval between a low water and the next high water. Synonym: rising tide, rise, flood.
  • RONIM: Réseaux d'observation du niveau de la mer (SHOM) (SHOM's sea level observation network)
  • ROSAME: Réseau d'Observation Subantarctique et Antarctique du niveau de la MER (LEGOS) (Sub-Antarctic and Antarctic sea level observation network)
  • Rule of sixths: expeditive method for calculating the current knowing its amplitude and the time of the maximum.



  • Saros: Period of 6585.3211 days corresponding to 223 lunations. At the end of this period, the Moon, the Sun, the node of the lunar orbit and the lunar perigee are in roughly the same relative situation.
  • SATANEM: Système d'Alerte aux Tsunamis en Atlantique Nord-Est et Méditerranée (North-East Atlantic and Mediterranean tsunami alert system).
  • SATOI: Système d'Alerte aux Tsunamis dans l'Océan Indien (Indian Ocean tsunami alert system)
  • SCHAPI: Service Central d'Hydrométéorologie et d'Appui à la prévision des inondations (Central hydrometrology and flood forecasting support system)
  • Semidiurnal tide with diurnal inequalities: two high waters and two low waters per day; the semi-diurnal components are dominant.
  • Semi-diurnal tide: two high waters and two low waters per day; the diurnal components are negligible.
  • Sensor: device that detects a physical phenomenon, in the form of a signal (usually electrical) in order to quantify and display it.
  • SGMer: Secrétariat Général de la MER (General secretariat for the sea)
  • SHC/CHS: Service Hydrographique Canadien/Canadian Hydrographic Service
  • SHOM: Service Hydrographique et Océanographique de la Marine (French navy hydrographic and oceanographic service)
  • Sidereal day: period of the Earth's rotation from vernal point to vernal point.
  • Sidereal revolution: time required for the mean longitude of the Moon, counted from a fixed equinox, to increase by 360°. It is equal to 27 days 7 hours and 43 minutes.
  • Situation: delay, measured as an angle between the maximum of the component and the maximum action of the corresponding element of the generating potential. This notion has been generalized for interaction components.
  • SMT/GTS: Système Mondial de Télécommunication/Global Telecommunications System
  • SO- INSU: Service d'Observation - Institut National des Sciences de l'Univers (Observation department of the national institute for universal sciences)
  • SOERE: Long term observation and experimentation system for environmental research.
  • Solar day: period of passage to the centre of the Sun of a meridian half-plane linked to the Earth.
  • Solstices: maximum declination of celestial bodies.
  • SONEL: Système d'observation des variations du niveau de la mer à long terme (Long-term sea level variation observation)
  • SPC-GD: Service de prévision des crues - Grand Delta (Flood forecasting service – Grand Delta)
  • SPC-LA: Service de prévision des crues – Littoral Atlantique (Flood forecasting service – Atlantic coast)
  • SPC-SACN: Service de prévision des crues - Seine Aval - Côtiers Normands (Flood forecasting service – Downstream Seine and Norman coasts)
  • SPC-VCB: Service de prévision des crues - Vilaine-Côtiers Bretons (Flood forecasting service – Vilaine and Breton coasts)
  • Spectral analysis: location in the frequency scale of the signals relating to the temporal variations of an observed magnitude.
  • Spectrum: graphic representation of the spectral component moduli.
  • Spring tide: maximum tidal range.
  • Stand: time interval during which the sea level remains practically stationary. Depending on the case we talk about low water stand and high water stand.
  • Swell: agitation of the surface of the water, with a regular crest that propagates roughly in the same direction as the others. When a perfect frequency is achieved, we talk of swell, swell being a series of identical, regular waves. In the absence of any clear organization, we talk of a choppy sea.
  • Synodic revolution: also known as the lunar month, it is the time interval between two full Moons and two new Moons.
  • Syzygy: moment at which the meridian planes of the Moon and the Sun are aligned. It corresponds to the Full Moon or the New Moon.



  • TAAF: French Southern and Antarctic Territories.
  • Tidal bore: wave accompanying the flood stream, observed in certain estuaries.
  • Tidal current: horizontal component of the gravitational action of the Moon and the Sun.
  • Tidal observatory: tidal observation site including the recording device, called a marigraph, the tidal scale and the levelling benchmarks placed nearby.
  • Tidal scale: Graduated scale used to read off the height of the tide directly with respect to the "scale datum", preferably located on the hydrographic datum.
  • Tide curve: graphic representation of the variations in the height of water.
  • Tide gauge: apparatus used to record vertical movements of the sea.
  • Tide: periodic movement of the sea level due to the effects of the gravitational action of the Moon and the Sun.
  • Tropical year: period of revolution of the sun on its orbit from vernal point to vernal point.
  • True anomaly: angle between the direction of the true sun and that of the perihelion.
  • Types of tide: diurnal tide, mixed tide, semi-diurnal tide and semi-diurnal tide with diurnal inequalities (see above).



  • UH: Unity of hydrometry
  • UHSLC: University of Hawaii Sea Level Center
  • ULR: Université de La Rochelle (La Rochelle university)
  • Under-keel clearance: safety margin to take account of random variations in the water level.
  • Unity of height: half tidal range of the mean equinoctial (semi-diurnal tide) or solstice spring tide (diurnal tide).
  • Universal Time: Greenwich civil time. Its acronym is UT.
  • UPF: Université de Polynésie française (University of French Polynesia)



  • Vernal point: spring equinoctial point.
  • Vertical: direction of a plumb line. With a degree of approximation, it is considered to be sufficient for problems relating to tides, that the vertical intersects the polar axis at the centre of the Earth.



  • Wave velocity: The speed of propagation of the tide wave
  • Wave: agitation of the surface of the water, with a regular crest that propagates roughly in the same direction as the others. When a perfect frequency is achieved, we talk of swell, swell being a series of identical, regular waves. In the absence of any clear organization, we talk of a choppy sea.





  • Zenith distance: angle between the direction of the zenith and the direction of the celestial body.
  • Zenith: the point where the direction of the PLUMB LINE produced above the HORIZON meets the celestial sphere (opposite of nadir).
  • ZH: Hydrographic datum.


Part of this Glossary is taken from the B. Simon's book (2007) "La marée. La marée océanique côtière" published by the Institut océanographique.


Last update of the portlet : 04/01/2012