Radiometric Calibration for Incidence Angle, Range and Sub-Footprint Effects on Hyperspectral LiDAR Backscatter Intensity

Changsai Zhang,Zheng Niu,Shuai Gao,Wang Li,Ni Huang,Kaiyi Bi,Gang Sun

doi:10.3390/rs12172855

Abstract

Terrestrial hyperspectral LiDAR (HSL) sensors could provide not only spatial information of the measured targets but also the backscattered spectral intensity signal of the laser pulse. The raw intensity collected by HSL is influenced by several factors, among which the range, incidence angle and sub-footprint play a significant role. Further studies on the influence of the range, incidence angle and sub-footprint are needed to improve the accuracy of backscatter intensity data as it is important for vegetation structural and biochemical information estimation. In this paper, we investigated the effects on the laser backscatter intensity and developed a practical correction method for HSL data. We established a laser ratio calibration method and a reference target-based method for HSL and investigated the calibration procedures for the mixed measurements of the effects of the incident angle, range and sub-footprint. Results showed that the laser ratio at the red-edge and near-infrared laser wavelengths has higher accuracy and simplicity in eliminating range, incident angle and sub-footprint effects and can significantly improve the backscatter intensity discrepancy caused by these effects.

Highlights

Light detection and ranging (LiDAR) has been acknowledged as a powerful survey tool to obtain surface geometry and to perform target characterization since its appearance over 20 years ago [1].In addition to 3D spatial geometric measurements, most LiDAR systems measure the returned laser signal power of the scanned object surfaces and record it as the intensity value at the same time
The laser ratio indices based on hyperspectral LiDAR (HSL) are used to test its potential for incidence angle, range and sub-footprint effects correction on the HSL backscatter intensity, while the reference target-based model is used as a baseline to compare the results
We explored the effects of the incidence angle, range and sub-footprint on HSL backscatter intensity measurements and proposed a practical correction method that maximizes the performance of hyperspectral LiDAR for different application fields of remote sensing

Summary

Introduction

Light detection and ranging (LiDAR) has been acknowledged as a powerful survey tool to obtain surface geometry and to perform target characterization since its appearance over 20 years ago [1].In addition to 3D spatial geometric measurements, most LiDAR systems measure the returned laser signal power of the scanned object surfaces and record it as the intensity value at the same time. The backscatter intensity is influenced by at least four essential factors [17], such as instrumental effects, atmospheric effects, scanning geometry and target scattering characteristics. The backscatter intensity is mainly influenced by scanning geometry, involving the incidence angle, range and sub-footprint, given that the instrumental influence is kept constant and atmospheric attenuation is negligible [18]. Considering such cases, a more comprehensive and robust intensity correction is needed to eliminate the effects of incidence angle, range and sub-footprint effects for the different applications of intensity data. The scanning geometry influence has been previously studied on intensity data

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