Remote Sensing of Sub-Surface Suspended Sediment Concentration by Using the Range Bias of Green Surface Point of Airborne LiDAR Bathymetry

Xinglei Zhao,Hongmei Zhang,Fengnian Zhou,Jianhu Zhao

doi:10.3390/rs10050681

Abstract

Suspended sediment concentrations (SSCs) have been retrieved accurately and effectively through waveform methods by using green-pulse waveforms of airborne LiDAR bathymetry (ALB). However, the waveform data are commonly difficult to analyze. Thus, this paper proposes a 3D point-cloud method for remote sensing of SSCs in calm waters by using the range biases of green surface points of ALB. The near water surface penetrations (NWSPs) of green lasers are calculated on the basis of the green and reference surface points. The range biases (ΔS) are calculated by using the corresponding NWSPs and beam-scanning angles. In situ measured SSCs (C) and range biases (ΔS) are used to establish an empirical C-ΔS model at SSC sampling stations. The SSCs in calm waters are retrieved by using the established C-ΔS model. The proposed method is applied to a practical ALB measurement performed by Optech Coastal Zone Mapping and Imaging LiDAR. The standard deviations of the SSCs retrieved by the 3D point-cloud method are less than 20 mg/L.

Highlights

Suspended sediment concentration (SSC) is an important parameter in studies of water quality, erosion, and aquatic ecological systems [1]
The direct method is ineffective in shallow waters, where the range of the volume backscatter return is short or missing in the raw pulse waveform [14]
The reference surface height is the basis of the 3D point-cloud method

Summary

Introduction

Suspended sediment concentration (SSC) is an important parameter in studies of water quality, erosion, and aquatic ecological systems [1]. The direct method uses fitting functions to directly fit the water column part in a raw pulse waveform. This method is simple and effective, and it can directly extract waveform parameters to retrieve SSC in deep waters. The direct method is ineffective in shallow waters, where the range of the volume backscatter return is short or missing in the raw pulse waveform [14]. The waveform parameters are calculated on the basis of the volume backscatter return separated from the raw pulse waveform to establish empirical SSC models and retrieve SSCs. the waveform methods are complex and inconvenient for applications because the waveform data are commonly difficult to analyze

Methods

Discussion

Conclusion