Analysis on the inversion accuracy of LAI based on simulated point clouds of terrestrial LiDAR of tree by ray tracing algorithm

Terrestrial LiDAR Scanning(TLS) technology can quickly acquire three-dimensional information of forest canopy with high precision. As a new technique of data collection, it has been gradually applied to characterize structural attributes such as plant area densities. This paper presented a ray-tracing method to simulate laser intersection with a single tree and retrieves the plant area index based on gap-fraction model. The simulation model, based on ray-tracing method, was highly dependent on the sensor configuration and the spatial characteristics of the tree examined. Plant area index was retrieved by the gap-fraction model using the simulated point clouds. Given the significant cost and complexity of LiDAR data acquisition, it was necessary to identify the operational parameters to maximize the benefit. Therefore, the factors that might affect the simulation and inversion procedures are discussed extensively. Results showed that the simulation model was capable of predicting what survey configuration would be optimal and facilitating inversion algorithm development.