Measurement of Trees Crown Projection Area and Volume Based on Airborne LiDAR Data

Abstract:

Airborne LiDAR can obtain threedimensional structural information of trees and get forest information by using points cloud classification and calculation method of crown projection area and volume. From the distribution of points cloud，the laser pulse formed an once echo when encountered the bare ground and roof of the building, and the distribution of the generated points cloud were smooth and continuous. The laser pulse penetrated vegetation would appear multiple echoes, the distribution rules of the points would be destroyed, and the distribution was in an irregular shape such as clusterlike. First, the points cloud of ground were extracted by using triangulated irregular network, then the points cloud of building were extracted by using planarfitting filtering algorithm. The points cloud of building were filtered to get points cloud of forest, and then the points cloud of forest were projected onto x-y plane. The edges of points cloud of timber were extracted by using the angle method; its corresponding image was displayed; the area of polygon was calculated by using area algorithm; then the calculation of the projection area of crown was achieved. In the study area, 10 experimental districts were randomly selected to carry out the traditional manual measurement. The experimental results showed that the projection area and volumes correlation coefficient of the two measurement methods were 0.957 and 0.944, respectively. The proposed method was feasible to achieve the accurate extraction of forest information rapidly and efficiently which includes a wide range of tree crown projection area and crown volume.