The Observation System for Long-term Variations in Sea Level (SONEL, formerly: Observation System of Nearshore Water Levels) is supported by two laboratories, (LEGOS-UMR 5566-CNRS-CNES-IRD-UPS, LIENSs-UMR 6250-CNRS-ULR) and two public agencies (IGN and SHOM).


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SONEL Framework: GLOSS


Internationally, SONEL falls within the scope of the Global Sea Level Observing System GLOSS, under the aegis of IOC/UNESCO (Merrifield et al., 2009). The scientific objective is to observe and understand long term variations in sea level components. The originality of the measuring system lies in synergy between the tidal measurements and space geodesy. The map shows the locations of the 300 or so tide gauge stations that are the global framework within which denser regional and local networks operate (Woodworth, 2009).

Situation des marégraphes GLOSS (Août 2012). Cliquer sur la carte pour accéder à la page SONEL relative.

Locations of GLOSS stations (August 2012). Map produced by SONEL


SONEL Framework: IGS International Service


SONEL is also involved in the activities of the international service IGS, meeting a request by the group of experts in the GLOSS programme to reference the tide gauges geodetically and monitor their vertical movements with respect to a stable, accurate terrestrial reference, such as the ITRF international benchmark (Neilan et al. 1998; Schoene et al. 2009). We should also point out that GLOSS and the IGS are international structures with voluntary participation, in other words they do not have any resources of their own other than for coordinating participations. The necessary resources for the French organizations' involvement per its commitments to the IOC must therefore be provided for by the State (IHO, 2009). Thus for obvious reasons, SONEL provides a national framework to the activities stemming from these worldwide programmes.


To find out more:


  • Merrifield, M., T. Aarup, A. Aman, P. Caldwell, R. M. S. Fernandes, H. Hayashibara, B. Kilonsky, B. Martin Miguez, G. Mitchum, B. Perez Gomez, L. Rickards, D. Rosen, T. Schöne, L. Testut, P. Woodworth, G. Wöppelmann, 2009. The Global Sea Level Observing System (GLOSS). In OceanObs'09, Ocean Information for society : sustaining the benefits, organizing the potential, Community White Papers, 21-25 September 2009, Venice, Italy. source.
  • Neilan, R., Van Scoy, P.A., Woodworth, P.L., (Ed.) 1998. Proceedings of the Workshop on methods for monitoring sea level : GPS and tide gauge benchmark monitoring, GPS altimeter calibration. Workshop organised by the IGS and PSMSL, Jet Propulsion Laboratory, 17-18 March 1997, 202 pp. Téléchargeable en fichiers pdf 2 parties) sur le site de la nasa.
  • OHI, 2009. Circular Letter 48/2009 07 july 2009, IHB File n° S3/2705.
  • Schoene T., G. Wöppelmann., S. Mazzotti, 2009. Report from Session 4 "Geodetic issues". Workshop on Precision Observations of Vertical Land Motion at Tide Gauges, Paris, UNESCO, 11-12 May 2009.
  • Woodworth P. L., L. J. Rickards, B. Pérez (2009). A survey of European sea level infrastructure, Nat. Hazards Earth Syst. Sci., 9, 927-934, doi:10.5194/nhess-9-927-2009.
  • Wöppelmann G., L. Testut et R. Creach (2011). La montée du niveau des océans par marégraphie et géodésie spatiale : contributions françaises à une problématique mondiale. Annales hydrographiques 2011, 6ème série, volume 8, n° 777, ISSN : 0373-3629.


Last updated: 12/12/2012

List of French programs:

List of programs, projects and reconstructions of tide gauge data