Precision of measuring the height of trees in various ways

Abstract

This study investigated the precision of measuring the height of trees using different methods. The paper evaluates the possibilities of using the stereophotogrammetric method to determine tree height indicators using unmanned aerial vehicles (UAV) in the conditions of a mature pine stand. The study compares the results of measuring the height of Scots pine trees with altimeters and height indicators determined from remote sensing data obtained using UAVs. In total, the study investigated six diverse ways to measure the height of growing trees. Experimental data on the height of the model trees were collected by three different altimeters (hand-held ground instruments) and the Phantom 4 Pro UAV. The use of UAVs involved optical capture and data collection using on-board equipment. Methods for determining the height of trees based on the results of processing data collected by quadcopter attachments were used. Specifically, the authors of this paper used the method of measuring the height of trees from a point cloud based on one-way vertical survey of model trees and calculating a digital crown height model (CHM) based on aerial photography of horizontal spans over a tree stand. The results of mathematical analysis of the conducted studies demonstrate the highest precision of the method using CHM to determine the height of growing trees. The value of the average random error in measuring the height of model trees using CHM was under 2%. The next most precise method of determining tree height was the TruPulse 360B laser-optical device, which demonstrated the highest precision among height meters. The use of the TruPulse 360b for ground-based measurements and the CHM method (based on UAV optical imaging data) yielded better results that meet the height precision standards for industrial inventory. Methods for determining the height of trees based on optical survey data from UAVs can be used for survey, inventory, forest management, and other works related to forestry and monitoring changes in forest ecosystems

Keywords

• unmanned aerial vehicle
• aerial photography
• stereophotogrammetry
• canopy height model
• altimeter