Analysis of Gedi's Elevation Accuracy from the First and Second Data Product Releases Over Inland Waterbodies
2022
Baghdadi, Nicolas | Fayad, Ibrahim | Frappart, Frédéric | Territoires, Environnement, Télédétection et Information Spatiale (UMR TETIS) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Interactions Sol Plante Atmosphère (UMR ISPA) ; Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
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Show more [+] Less [-]English. In this study, water level estimates from the Global Ecosystem Dynamics Investigation Lidar (GEDI) were validated against in situ gauge station records over Lake Geneva. The performances of the first and second releases (respectively V1 and V2) of the GEDI data products were compared. The influence of the following parameters were analyzed: (1) the signal-over-noise ratio (SNR), (2) the width of water surface peak within the waveform (gwidth), (3) the amplitude of the water surface peak within the waveform (A), (4) the viewing angle of GEDI (VA), and (5) the acquiring beam. The comparison between V1 and V2 elevations showed that V2, overall, provided elevations with a more constant bias and fewer deviations to in situ data than V1. In addition, by choosing GEDI shots with VA ≤ 3.5°, the unbiased RMSE (ubRMSE) of GEDI elevations was 27.1 cm with V2 (r=0.66) and 42.8 cm with V1 (r=0.34). Results also show that the accuracy of GEDI (ubRMSE) does not seem to depend on the beam number and GEDI acquisition dates for the most accurate GEDI acquisitions (VA≤ 3.5°). Regarding the bias, a higher value was observed with V2 but with lower variability (54 cm) in comparison to V1 (35 cm). Finally, the bias showed a slight dependence on beam GEDI number.
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