Full-Waveform LiDAR Fast Analysis of a Moderately Turbid Bay in Western France

Type Article
Date 2019-01
Language English
Author(s) Launeau Patrick1, Giraud Manuel1, Robin Marc2, Baltzer Agnes2
Affiliation(s) 1 : Laboratoire de Planétologie et Géodynamique, UMR CNRS 6112, Université de Nantes, 2 rue de la Houssinière, 44322 Nantes, France
2 : Littoral Environnement Télédétection Géomatique, UMR CNRS 6554, Université de Nantes, Campus Tertre, 44312 Nantes, France
Source Remote Sensing (2072-4292) (MDPI AG), 2019-01 , Vol. 11 , N. 2 , P. 117 (23p.)
DOI 10.3390/rs11020117
WOS© Times Cited 8
Keyword(s) full-waveform, airborne LiDAR, bathymetry, shoreline monitoring, turbidity
Abstract

In shoreline monitoring, only topo-bathymetric light detection and ranging (LiDAR) can map large corridors from aerial dunes to sandbanks in shallow water. Increasing turbidity masking the formation of 532 nm laser beam echoes on the sea bed makes this challenging. Full-waveform recording all the laser beam damping functions, a turbid water column can be seen as an accumulation of layers forming a single continuum and a distinction can be made between signals ending at the bottom down to a depth of 10 m. In practice full-waveforms are converted by laser beam tracing an image cube with a grid of 1-m-wide pixels and a 0.15 m range resolution storing the mean intensities returned along incident angle. The first derivative of a wide Gaussian filter serves to delineate the full-waveform range limits. Because of turbidity current heterogeneity and complexity of multiple layers radiative transfer model, a drastic simplification is applied by normalizing the cumulative full-waveform to 1, transforming each pixel of the water column into spectrum of intensity ranging from 0 to 1 from bottom to top. A transposition between range and bottom-top information facilitates the water index correction below the sea water level provided by 1064-nm discrete echoes. All echoes remain accessible with maximums of cumulative full-waveform third derivative.

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