Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes
Radar altimetry is now commonly used to provide long-term monitoring of inland water levels in complement to or for replacing disappearing in situ networks of gauge stations. Recent improvements in tracking and acquisition modes improved the quality the water retrievals. The newly implemented Open L...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-06-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/13/11/2196 |
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| author | Frédéric Frappart Fabien Blarel Ibrahim Fayad Muriel Bergé-Nguyen Jean-François Crétaux Song Shu Joël Schregenberger Nicolas Baghdadi |
| author_facet | Frédéric Frappart Fabien Blarel Ibrahim Fayad Muriel Bergé-Nguyen Jean-François Crétaux Song Shu Joël Schregenberger Nicolas Baghdadi |
| author_sort | Frédéric Frappart |
| collection | DOAJ |
| description | Radar altimetry is now commonly used to provide long-term monitoring of inland water levels in complement to or for replacing disappearing in situ networks of gauge stations. Recent improvements in tracking and acquisition modes improved the quality the water retrievals. The newly implemented Open Loop mode is likely to increase the number of monitored water bodies owing to the use of an a priori elevation, especially in hilly and mountainous areas. The novelty of this study is to provide a comprehensive evaluation of the performances of the past and current radar altimetry missions according to their acquisition (Low Resolution Mode or Synthetic Aperture Radar) and tracking (close or open loop) modes, and acquisition frequency (Ku or Ka) in a mountainous area where tracking losses of the signal are likely to occur, as well as of the recently launched ICESat-2 and GEDI lidar missions. To do so, we evaluate the quality of water level retrievals from most radar altimetry missions launched after 1995 over eight lakes in Switzerland, using the recently developed ALtimetry Time Series software, to compare the performances of the new tracking and acquisition modes and also the impact of the frequency used. The combination of the Open Loop tracking mode with the Synthetic Aperture Radar acquisition mode on SENTINEL-3A and B missions outperforms the classical Low Resolution Mode of the other missions with a lake observability greater than 95%, an almost constant bias of (−0.17 ± 0.04) m, a RMSE generally lower than 0.07 m and a R most of the times higher than 0.85 when compared to in situ gauge records. To increase the number of lakes that can be monitored and the temporal sampling of the water level retrievals, data acquired by lidar altimetry missions were also considered. Very accurate results were also obtained with ICESat-2 data with RMSE lower than 0.06 and R higher than 0.95 when compared to in situ water levels. An almost constant bias (0.42 ± 0.03) m was also observed. More contrasted results were obtained using GEDI. As these data were available on a shorter time period, more analyses are necessary to determine their potential for retrieving water levels. |
| first_indexed | 2024-03-10T10:42:47Z |
| format | Article |
| id | doaj.art-3d831a7957f0488da3502241096f6afd |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T10:42:47Z |
| publishDate | 2021-06-01 |
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| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-3d831a7957f0488da3502241096f6afd2023-11-21T22:49:52ZengMDPI AGRemote Sensing2072-42922021-06-011311219610.3390/rs13112196Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss LakesFrédéric Frappart0Fabien Blarel1Ibrahim Fayad2Muriel Bergé-Nguyen3Jean-François Crétaux4Song Shu5Joël Schregenberger6Nicolas Baghdadi7LEGOS, Université de Toulouse (CNES/CNRS/IRD/UPS), 14 Avenue Edouard Belin, 31400 Toulouse, FranceLEGOS, Université de Toulouse (CNES/CNRS/IRD/UPS), 14 Avenue Edouard Belin, 31400 Toulouse, FranceCIRAD, CNRS, INRAE, TETIS, University of Montpellier, AgroParisTech, CEDEX 5, 34093 Montpellier, FranceLEGOS, Université de Toulouse (CNES/CNRS/IRD/UPS), 14 Avenue Edouard Belin, 31400 Toulouse, FranceLEGOS, Université de Toulouse (CNES/CNRS/IRD/UPS), 14 Avenue Edouard Belin, 31400 Toulouse, FranceDepartment of Geography and Planning, Appalachian State University, Boone, NC 28608, USAEidg. Departement für Umwelt, Verkehr, Energie und Kommunikation UVEK, Bundesamt für Umwelt BAFU, Abteilung Hydrologie, 3003 Bern, SwitzerlandCIRAD, CNRS, INRAE, TETIS, University of Montpellier, AgroParisTech, CEDEX 5, 34093 Montpellier, FranceRadar altimetry is now commonly used to provide long-term monitoring of inland water levels in complement to or for replacing disappearing in situ networks of gauge stations. Recent improvements in tracking and acquisition modes improved the quality the water retrievals. The newly implemented Open Loop mode is likely to increase the number of monitored water bodies owing to the use of an a priori elevation, especially in hilly and mountainous areas. The novelty of this study is to provide a comprehensive evaluation of the performances of the past and current radar altimetry missions according to their acquisition (Low Resolution Mode or Synthetic Aperture Radar) and tracking (close or open loop) modes, and acquisition frequency (Ku or Ka) in a mountainous area where tracking losses of the signal are likely to occur, as well as of the recently launched ICESat-2 and GEDI lidar missions. To do so, we evaluate the quality of water level retrievals from most radar altimetry missions launched after 1995 over eight lakes in Switzerland, using the recently developed ALtimetry Time Series software, to compare the performances of the new tracking and acquisition modes and also the impact of the frequency used. The combination of the Open Loop tracking mode with the Synthetic Aperture Radar acquisition mode on SENTINEL-3A and B missions outperforms the classical Low Resolution Mode of the other missions with a lake observability greater than 95%, an almost constant bias of (−0.17 ± 0.04) m, a RMSE generally lower than 0.07 m and a R most of the times higher than 0.85 when compared to in situ gauge records. To increase the number of lakes that can be monitored and the temporal sampling of the water level retrievals, data acquired by lidar altimetry missions were also considered. Very accurate results were also obtained with ICESat-2 data with RMSE lower than 0.06 and R higher than 0.95 when compared to in situ water levels. An almost constant bias (0.42 ± 0.03) m was also observed. More contrasted results were obtained using GEDI. As these data were available on a shorter time period, more analyses are necessary to determine their potential for retrieving water levels.https://www.mdpi.com/2072-4292/13/11/2196radar and laser altimetrylakesvalidation |
| spellingShingle | Frédéric Frappart Fabien Blarel Ibrahim Fayad Muriel Bergé-Nguyen Jean-François Crétaux Song Shu Joël Schregenberger Nicolas Baghdadi Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes Remote Sensing radar and laser altimetry lakes validation |
| title | Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes |
| title_full | Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes |
| title_fullStr | Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes |
| title_full_unstemmed | Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes |
| title_short | Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes |
| title_sort | evaluation of the performances of radar and lidar altimetry missions for water level retrievals in mountainous environment the case of the swiss lakes |
| topic | radar and laser altimetry lakes validation |
| url | https://www.mdpi.com/2072-4292/13/11/2196 |
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