Interpretation of Spectral LiDAR Backscattering off the Florida Coast

Martin A Montes,Ben Metzger,Anni K Vuorenkoski,Bryan Botson

doi:10.3390/rs13132475

Abstract

A multispectral backscattering LiDAR (Light detection and range) system (hereafter Oculus) was integrated into a wave glider and used to estimate the scattering order (i.e., single vs multiple collisions) of LIDAR backscattering, the water inherent optical properties (IOPs), the biogeo-chemical characteristics of particulate scatterers (i.e., relative size, composition) and their motion) on shelf waters of South East Florida. Oculus has a dual-wavelength configuration (473 and 532 nm) and two detection geometries (off- and on-axis). Characteristics of scatterers were investigated based on two complementary LiDAR-derived proxies (the Structural Dissimilarity Index and the spectral slope of LiDAR backscattering). In March 2017, field measurements showed a covariation between direct and diffuse backscattering contributions during morning hours and away from shore. LiDAR attenuation coefficients explained up to 57% of IOPs variability. The analysis of LiDAR-derived proxies suggested higher turbidity and larger particulates near the coast

Highlights

The characterization of underwater scatterers based on light and range detection (LiDAR) measurements has been fundamental in studies related to the mapping of turbidity plumes [1] and thin scattering layers [2]
The accurate detection and identification of relatively large scatterers [8] highly relies on how well the ‘background’ scattering of the optical medium is removed. This baseline signal is determined by the inherent optical properties (IOPs) of the waters under investigation and is critical for optimizing LiDAR-based imagers of underwater features [9]
For on-axis signals, the exponential decay phase was extended up to 210 ns after which the tail was characterized by a change of slope due likely to a greater contribution of multiple scattering

Summary

Introduction

The characterization of underwater scatterers based on light and range detection (LiDAR) measurements has been fundamental in studies related to the mapping of turbidity plumes [1] and thin scattering layers [2]. The composition of scattering layers has been largely unknown for more than one decade due in part to the poor spectral resolution of LiDAR systems for water applications To cope with this limitation, different techniques based on hybrid information (e.g., spectral reflectance and LiDAR backscattering) [3], relationships between optical properties derived from. The accurate detection and identification of relatively large scatterers (i.e., size parameter = π D/λ >> 1, where D is the scatterer diameter and λ is the wavelength) [8] highly relies on how well the ‘background’ scattering of the optical medium is removed This baseline signal is determined by the inherent optical properties (IOPs) of the waters under investigation and is critical for optimizing LiDAR-based imagers of underwater features [9]

Methods

Results

Discussion

Conclusion