A Study of Energy Attenuation Due to Forest Canopy in Small- Footprint Waveform Lidar Signals

Waveform light detection and ranging (wLiDAR) records the entire backscattered signal of an emitted laser pulse, enabling deeper penetration through tree canopy. However, due to interactions (e.g. reflection, absorption, and transmission) within the canopy, the full proportion of emitted light may not reach the ground, resulting in an attenuated waveform. Correction of attenuation will result in improved understanding of below-canopy responses, which is important for terrain mapping, biomass estimation, leaf area assessment, etc. In this study we use a simulation environment to study attenuation behavior and its dependence on factors within the canopy, such as number of interactions, absorptivity of encountered objects, scene geometry relative to emitted laser beam, and vertical spacing within the canopy. All of these factors influence the rate of attenuation and we conclude that the waveform may be corrected by a factor that is proportional to the sum of areas under the Gaussian curves of all preceding interactions.