{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T18:49:49Z","timestamp":1775155789269,"version":"3.50.1"},"reference-count":37,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2022,2,10]],"date-time":"2022-02-10T00:00:00Z","timestamp":1644451200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Monitoring chlorophyll-a concentration or turbidity is crucial for understanding and managing oligo- to mesotrophic coastal waters quality. However, mapping bio-optical components from space in such shallow settings remains challenging because of the strong interference of the complex bathymetry and various seabed colors. Correcting the total satellite reflectance signal from the seabed reflectance in ocean color with high resolution sensors is promising. This article shows how unsupervised clustering approaches can be applied to Sentinel-2 images to classify seabed colors in shallow waters of a tropical oligotrophic lagoon in New Caledonia. Data processing included Lyzenga correction for estimating the water column reflectance, optical spectra standardization for attenuating water absorption effects and clustering using the unsupervised k-means method. This methodological approach was applied on the 497, 560, 664 and 704 nm optical bands of the selected Sentinel-2 image. When applied on non-standardized data, our unsupervised classification retrieved three seafloor clusters, whereas five seafloor clusters could be retrieved using standardized data. For each of these two trials, the computed membership values explained more than 75% of the inertia in each Sentinel-2 wavelength band used for the clustering. However, the accuracy of the method was slightly improved when applied on standardized data. Confusion index mapping of the unsupervised clustering retrieved from these data emphasized the relevance and robustness of our methodological approach. Such an approach for seabed colors classification in optically complex shallow settings will be particularly helpful to improve remote sensing of biogeochemical indicators such as chlorophyll-a concentration and turbidity in fragile coastal environments.<\/jats:p>","DOI":"10.3390\/rs14040836","type":"journal-article","created":{"date-parts":[[2022,2,11]],"date-time":"2022-02-11T02:40:17Z","timestamp":1644547217000},"page":"836","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Unsupervised Optical Classification of the Seabed Color in Shallow Oligotrophic Waters from Sentinel-2 Images: A Case Study in the Voh-Kon\u00e9-Pouembout Lagoon (New Caledonia)"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1564-0636","authenticated-orcid":false,"given":"Guillaume","family":"Wattelez","sequence":"first","affiliation":[{"name":"Interdisciplinary Laboratory for Research in Education, EA 7483, University of New Caledonia, Avenue James Cook, Noumea 98800, New Caledonia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2246-918X","authenticated-orcid":false,"given":"C\u00e9cile","family":"Dupouy","sequence":"additional","affiliation":[{"name":"Mediterranean Institute of Oceanography (MIO), Aix-Marseille Universit\u00e9, CNRS\/INSU, Universit\u00e9 de Toulon, IRD, UM 110, 13288 Marseille, France"},{"name":"Centre IRD Noumea, Noumea 98848, New Caledonia"}]},{"given":"Farid","family":"Juillot","sequence":"additional","affiliation":[{"name":"Centre IRD Noumea, Noumea 98848, New Caledonia"},{"name":"Institut de Min\u00e9ralogie, de Physique des Mat\u00e9riaux et de Cosmochimie (IMPMC), ERL IRD 206, UMR CNRS 7590, MNHN, Sorbonne Universit\u00e9, 75005 Paris, France"}]}],"member":"1968","published-online":{"date-parts":[[2022,2,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1016\/j.marpolbul.2010.06.020","article-title":"Integrated Coastal Zone Management Perspectives to Ensure the Sustainability of Coral Reefs in New Caledonia","volume":"61","author":"David","year":"2010","journal-title":"Mar. Pollut. Bull."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Leopold, M., Sourisseau, J.-M., Cornuet, N., David, C., Bonmarchand, A., Le Meur, P.-Y., Lasseigne, L., Poncet, E., Toussaint, M., and Fontenelle, G. (2013). La gestion d\u2019un lagon en mutation: Acteurs, enjeux et recherche-action en Nouvelle-Cal\u00e9donie (Pacifique sud). Vertigo, 13.","DOI":"10.4000\/vertigo.13297"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"7021","DOI":"10.1002\/ece3.6405","article-title":"Regionally scalable habitat typology for assessing benthic habitats and fish communities: Application to New Caledonia reefs and lagoons","volume":"10","author":"Pelletier","year":"2020","journal-title":"Ecol. Evol."},{"key":"ref_4","unstructured":"Sathyendranath, S. (2000). Remote sensing of ocean color in coastal, and other optically-complex waters. Reports of the International Ocean-Colour Coordinating Group, No. 3, IOCCG."},{"key":"ref_5","unstructured":"Morel, A. (1998). Minimum requirements for an operational, ocean-colour sensor for the open ocean. Reports of the International Ocean-Colour Coordinating Group, No. 1, IOCCG."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1489","DOI":"10.1007\/s10712-020-09594-5","article-title":"Earth Observations for Monitoring Marine Coastal Hazards and Their Drivers","volume":"41","author":"Melet","year":"2020","journal-title":"Surv. Geophys."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1016\/j.marpolbul.2010.06.039","article-title":"Inherent optical properties and satellite retrieval of chlorophyll concentration in the lagoon and open waters of New Caledonia","volume":"61","author":"Dupouy","year":"2010","journal-title":"Mar. Pollut. Bull."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"4165","DOI":"10.3390\/s8074165","article-title":"Optical Algorithms at Satellite Wavelengths for Total Suspended Matter in Tropical Coastal Waters","volume":"8","author":"Ouillon","year":"2008","journal-title":"Sensors"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1724","DOI":"10.1109\/TGRS.2003.815408","article-title":"Sea surface correction of high spatial resolution Ikonos images to improve bottom mapping in near-shore environments","volume":"41","author":"Hochberg","year":"2003","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1689","DOI":"10.4319\/lo.1994.39.7.1689","article-title":"Diffuse reflectance of oceanic shallow waters: Influence of water depth and bottom albedo","volume":"39","author":"Maritorena","year":"1994","journal-title":"Limnol. Oceanogr."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Wattelez, G., Dupouy, C., Mangeas, M., Lef\u00e8vre, J., and Frouin, R. (2016). A statistical algorithm for estimating Chlorophyll Concentration in the New Caledonian lagoon. Remote Sens., 8.","DOI":"10.3390\/rs8010045"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Wattelez, G., Dupouy, C., Juillot, F., Fernandez, J.M., Lef\u00e8vre, J., and Ouillon, S. (2017). Remotely-sensed assessment of turbidity with MODIS in the oligotrophic lagoon of Voh-Kon\u00e9-Pouembout area, New Caledonia. Water, 9.","DOI":"10.3390\/w9100737"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1364\/AO.38.003831","article-title":"Hyperspectral remote sensing for shallow waters: 2. Deriving bottom depths and water properties by optimization","volume":"38","author":"Lee","year":"1999","journal-title":"Appl. Opt."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"396","DOI":"10.4319\/lom.2011.9.396","article-title":"Intercomparison of shallow water bathymetry, hydro-optics, and benthos mapping techniques in Australian and Caribbean coastal environments","volume":"9","author":"Dekker","year":"2011","journal-title":"Limnol. Oceanogr. Methods"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1080\/01431168108948342","article-title":"Remote sensing of bottom reflectance and water attenuation parameters in shallow water using aircraft and LANDSAT data","volume":"2","author":"Lyzenga","year":"1981","journal-title":"Int. J. Remote Sens."},{"key":"ref_16","first-page":"2617","article-title":"Correction of the water column attenuation: Application to the seabed mapping of the lagoon of New Caledonia using MERIS images","volume":"7","author":"Dupouy","year":"2014","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.margeo.2015.01.006","article-title":"Objective automated classification technique for marine landscape mapping in submarine canyons","volume":"362","author":"Ismail","year":"2015","journal-title":"Mar. Geol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1236","DOI":"10.1016\/j.csr.2011.04.016","article-title":"Unsupervised fuzzy classification and object-based image analysis of multibeam data to map deep water substrates, Cook Strait, New Zealand","volume":"31","author":"Lucieer","year":"2011","journal-title":"Cont. Shelf Res."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Toming, K., Kutser, T., Laas, A., Sepp, M., Paavel, B., and N\u00f5ges, T. (2016). First experiences in mapping lake water quality parameters with Sentinel-2 MSI imagery. Remote Sens., 8.","DOI":"10.3390\/rs8080640"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1016\/j.rse.2017.08.033","article-title":"Sentinel-2 multispectral instrument (MSI) data processing for aquatic science applications: Demonstrations and validations","volume":"201","author":"Pahlevan","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1016\/j.rse.2011.06.028","article-title":"Capability of the Sentinel-2 mission for tropical coral reef mapping and coral bleaching detection","volume":"120","author":"Hedley","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"598","DOI":"10.1016\/j.rse.2018.07.014","article-title":"Coral reef applications of Sentinel-2: Coverage, characteristics, bathymetry and benthic mapping with comparison to Landsat 8","volume":"216","author":"Hedley","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"739","DOI":"10.1109\/JSTARS.2013.2239260","article-title":"Influence of water column chlorophyll concentration on bathymetric estimations in the lagoon of New Caledonia, using several MERIS images","volume":"6","author":"Dupouy","year":"2013","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_24","unstructured":"Shom-IRD (2022, February 06). MNT Bathym\u00e9trique de Fa\u00e7ade de la Nouvelle-Cal\u00e9donie (Projet TSUCAL). Available online: http:\/\/dx.doi.org\/10.17183\/MNT_NC100m_TSUCAL_WGS84."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1016\/j.rse.2019.04.027","article-title":"A global approach for chlorophyll-a retrieval across optically complex inland waters based on optical water types","volume":"229","author":"Neil","year":"2019","journal-title":"Remote Sens. Environ."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1016\/j.marpolbul.2010.06.023","article-title":"Circulation and suspended sediment transport in a coral reef lagoon: The south-west lagoon of New Caledonia","volume":"61","author":"Ouillon","year":"2010","journal-title":"Mar. Pollut. Bull."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"309","DOI":"10.1016\/j.marpolbul.2010.06.021","article-title":"Biogeochemical typology and temporal variability of lagoon waters in a coral reef ecosystem subject to terrigeneous and anthropogenic inputs (New Caledonia)","volume":"61","author":"Fichez","year":"2010","journal-title":"Mar. Pollut. Bull."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2668","DOI":"10.3390\/rs70302668","article-title":"A Multi-temporal and multispectral method to estimate aerosol optical thickness over land, for the atmospheric correction of FormoSat-2, LandSat, VEN\u03bcS and Sentinel-2 images","volume":"7","author":"Hagolle","year":"2015","journal-title":"Remote Sens."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1016\/j.rse.2019.01.018","article-title":"Evaluation of Sentinel-2 time-series for mapping floodplain grassland plant communities","volume":"223","author":"Rapinel","year":"2019","journal-title":"Remote Sens. Environ."},{"key":"ref_30","unstructured":"Kirk, J.T.O. (2022, February 06). Light and Photosynthesis in Aquatic Ecosystems. Marine Optics, Available online: https:\/\/catalogue.nla.gov.au\/Record\/229672."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"16881","DOI":"10.3390\/s140916881","article-title":"Water Column Correction for Coral Reef Studies by Remote Sensing","volume":"14","author":"Zoffoli","year":"2014","journal-title":"Sensors"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1080\/10106049.2012.756940","article-title":"Data fusion and classifier ensemble techniques for vegetation mapping in the coastal Everglades","volume":"29","author":"Zhang","year":"2014","journal-title":"Geocarto Int."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"230","DOI":"10.1016\/j.margeo.2009.06.006","article-title":"Fuzzy clustering for seafloor classification","volume":"264","author":"Lucieer","year":"2009","journal-title":"Mar. Geol."},{"key":"ref_34","unstructured":"R Core Team (2014). R: A Language and Environment for Statistical Computing, R Foundation for Statistical Computing."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"100","DOI":"10.2307\/2346830","article-title":"Algorithm AS 136: A K-means clustering algorithm","volume":"28","author":"Hartigan","year":"1979","journal-title":"Appl. Stat."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"34838","DOI":"10.1364\/OE.27.034838","article-title":"Optical classification of inland waters based on an improved Fuzzy C-Means method","volume":"27","author":"Bi","year":"2019","journal-title":"Opt. Express"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2841","DOI":"10.1093\/bioinformatics\/btq534","article-title":"A simple and fast method to determine the parameters for fuzzy c-means cluster analysis","volume":"26","author":"Jensen","year":"2010","journal-title":"Bioinformatics"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/4\/836\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:17:52Z","timestamp":1760134672000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/4\/836"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,2,10]]},"references-count":37,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2022,2]]}},"alternative-id":["rs14040836"],"URL":"https:\/\/doi.org\/10.3390\/rs14040836","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,2,10]]}}}