Common use of LIDAR Method Clause in Contracts

LIDAR Method. The method used to build these linear regression models is described in further detail in Section 3, the LIDAR Method for Canopy Height. Two models were developed to estimate crown diameter from LIDAR. The first used only metrics derived directly from the LIDAR data itself. The second could include radius or diameter values calculated from the individual tree objects (ITOs) created during the segmentation of the 6 ft. resolution canopy height model (CHM). The process of segmenting the canopy model into individual tree objects (i.e. portions of LiDAR point cloud assumed to represent individual trees) is described further in Appendix D. Two models were developed because it was believed that ITOs provide additional information about the trees on the plot, and could potentially improve the accuracy of the crown diameter model. However, segmenting a canopy height model and measuring diameters and radii of the resulting ITOs, is time consuming. The additional processing time, may outweigh the value of any additional accuracy. In Table 5 below, we describe the different crown size metrics that were calculated for each tree object. These were averaged for the trees objects on each plot. The plot averages were included as possible metrics in the regression models. The center of the tree, the high point, is the center of the cell with the highest height in the tree object, and can be considered the stem location. Each tree object has 16 vertices in the cardinal directions, at the cell centers nearest the edges of the crown. Distances from the high point to each vertex were calculated and used for the crown size metrics. Table 5. Diameter and radius metrics calculated for each tree object. Maximum Radius The longest radius from the high point (the furthest vertex). Minimum Radius The shortest radius from the high point (the closest vertex). Longest and Perpendicular Diameter The diameter based on averaging the longest transect with the transect perpendicular to the longest transect. NS/EW Average Diameter The diameter based on averaging the North/South transect and the East/West transect lengths; these may not be the longest transects. Average Radii Diameter The diameter based on averaging the lengths of all the radii from the high point to each vertex, and doubling the average. Crown Area Diameter The diameter based on treating the polygon as a circle and back- calculating the diameter from the circle’s area.