{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T17:41:00Z","timestamp":1775842860968,"version":"3.50.1"},"reference-count":49,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2018,2,24]],"date-time":"2018-02-24T00:00:00Z","timestamp":1519430400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002830","name":"CNES","doi-asserted-by":"publisher","award":["CTOH"],"award-info":[{"award-number":["CTOH"]}],"id":[{"id":"10.13039\/501100002830","id-type":"DOI","asserted-by":"publisher"}]},{"name":"INSU EC2CO","award":["RALTERAC"],"award-info":[{"award-number":["RALTERAC"]}]},{"DOI":"10.13039\/100014596","name":"TNC","doi-asserted-by":"publisher","award":["RALTERAC"],"award-info":[{"award-number":["RALTERAC"]}],"id":[{"id":"10.13039\/100014596","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Radar altimetry is now commonly used for the monitoring of water levels in large river basins. In this study, an altimetry-based network of virtual stations was defined in the quasi ungauged Ogoou\u00e9 river basin, located in Gabon, Central Africa, using data from seven altimetry missions (Jason-2 and 3, ERS-2, ENVISAT, Cryosat-2, SARAL, Sentinel-3A) from 1995 to 2017. The performance of the five latter altimetry missions to retrieve water stages and discharges was assessed through comparisons against gauge station records. All missions exhibited a good agreement with gauge records, but the most recent missions showed an increase of data availability (only 6 virtual stations (VS) with ERS-2 compared to 16 VS for ENVISAT and SARAL) and accuracy (RMSE lower than 1.05, 0.48 and 0.33 and R\u00b2 higher than 0.55, 0.83 and 0.91 for ERS-2, ENVISAT and SARAL respectively). The concept of VS is extended to the case of drifting orbits using the data from Cryosat-2 in several close locations. Good agreement was also found with the gauge station in Lambar\u00e9n\u00e9 (RMSE = 0.25 m and R2 = 0.96). Very good results were obtained using only one year and a half of Sentinel-3 data (RMSE &lt; 0.41 m and R2 &gt; 0.89). The combination of data from all the radar altimetry missions near Lamabr\u00e9n\u00e9 resulted in a long-term (May 1995 to August 2017) and significantly improved water-level time series (R\u00b2 = 0.96 and RMSE = 0.38 m). The increase in data sampling in the river basin leads to a better water level peak to peak characterization and hence to a more accurate annual discharge over the common observation period with only a 1.4 m3\u00b7s\u22121 difference (i.e., 0.03%) between the altimetry-based and the in situ mean annual discharge.<\/jats:p>","DOI":"10.3390\/rs10020350","type":"journal-article","created":{"date-parts":[[2018,2,27]],"date-time":"2018-02-27T03:36:12Z","timestamp":1519702572000},"page":"350","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":87,"title":["Monitoring Water Levels and Discharges Using Radar Altimetry in an Ungauged River Basin: The Case of the Ogoou\u00e9"],"prefix":"10.3390","volume":"10","author":[{"given":"Sakaros","family":"Bogning","sequence":"first","affiliation":[{"name":"D\u00e9partement de Sciences de la Terre, Universit\u00e9 de Douala, BP 24 157 Douala, Cameroun"},{"name":"Jeune Equipe Associ\u00e9e \u00e0 l\u2019IRD\u2014R\u00e9ponse du Littoral Camerounais aux For\u00e7ages Oc\u00e9aniques Multi-\u00c9chelles (JEAI-RELIFOME), Universit\u00e9 de Douala, BP 24 157 Douala, Cameroun"},{"name":"LEGOS, Universit\u00e9 de Toulouse, CNES, CNRS, IRD, UPS OMP, 14 Av. E. Belin, 31400 Toulouse, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4661-8274","authenticated-orcid":false,"given":"Fr\u00e9d\u00e9ric","family":"Frappart","sequence":"additional","affiliation":[{"name":"LEGOS, Universit\u00e9 de Toulouse, CNES, CNRS, IRD, UPS OMP, 14 Av. E. Belin, 31400 Toulouse, France"},{"name":"GET, Universit\u00e9 de Toulouse, CNRS, IRD, UPS OMP, 14 Av. E. Belin, 31400 Toulouse, France"}]},{"given":"Fabien","family":"Blarel","sequence":"additional","affiliation":[{"name":"LEGOS, Universit\u00e9 de Toulouse, CNES, CNRS, IRD, UPS OMP, 14 Av. E. Belin, 31400 Toulouse, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7475-6017","authenticated-orcid":false,"given":"Fernando","family":"Ni\u00f1o","sequence":"additional","affiliation":[{"name":"LEGOS, Universit\u00e9 de Toulouse, CNES, CNRS, IRD, UPS OMP, 14 Av. E. Belin, 31400 Toulouse, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0081-750X","authenticated-orcid":false,"given":"Gil","family":"Mah\u00e9","sequence":"additional","affiliation":[{"name":"HydroSciences Montpellier, Universit\u00e9 de Montpellier, CNRS, IRD, 300 Av. Pr E. Jeanbrau, 34090 Montpellier, France"}]},{"given":"Jean-Pierre","family":"Bricquet","sequence":"additional","affiliation":[{"name":"HydroSciences Montpellier, Universit\u00e9 de Montpellier, CNRS, IRD, 300 Av. Pr E. Jeanbrau, 34090 Montpellier, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3609-7524","authenticated-orcid":false,"given":"Fr\u00e9d\u00e9rique","family":"Seyler","sequence":"additional","affiliation":[{"name":"ESPACE-DEV, Universit\u00e9 de Montpellier, IRD, Universit\u00e9 des Antilles, Universit\u00e9 de Guyane, Universit\u00e9 de La R\u00e9union, Maison de la T\u00e9l\u00e9d\u00e9tection, 500 Rue J-F. Breton, 34093 Montpellier, France"}]},{"given":"Rapha\u00ebl","family":"Ongu\u00e9n\u00e9","sequence":"additional","affiliation":[{"name":"Jeune Equipe Associ\u00e9e \u00e0 l\u2019IRD\u2014R\u00e9ponse du Littoral Camerounais aux For\u00e7ages Oc\u00e9aniques Multi-\u00c9chelles (JEAI-RELIFOME), Universit\u00e9 de Douala, BP 24 157 Douala, Cameroun"}]},{"given":"Jacques","family":"Etam\u00e9","sequence":"additional","affiliation":[{"name":"D\u00e9partement de Sciences de la Terre, Universit\u00e9 de Douala, BP 24 157 Douala, Cameroun"}]},{"given":"Marie-Claire","family":"Paiz","sequence":"additional","affiliation":[{"name":"The Nature Conservancy Gabon Program Office, Lot 114 Haut de Gu\u00e9-Gu\u00e9, 13553 Libreville, Gabon"}]},{"given":"Jean-Jacques","family":"Braun","sequence":"additional","affiliation":[{"name":"GET, Universit\u00e9 de Toulouse, CNRS, IRD, UPS OMP, 14 Av. E. 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