Automated low-cost terrestrial laser scanner for measuring diameters at breast height and heights of plantation trees.

Guochao Bu,Rui Zhao,Ronghao Li,Pei Wang

doi:10.1371/journal.pone.0209888

Abstract

A terrestrial laser scanner is a fast, high-precision data acquisition device, which has been applied more and more to the research area of forest inventory. In this study, a type of automated low-cost terrestrial laser scanner was designed and implemented based on a SICK LMS-511 two-dimensional laser scanning sensor and a stepper motor. The new scanner was named BEE(developed by the department of Electronic Engineering, Beijing Forestry University), which can scan the forest trees in three dimensions. The BEE scanner and its supporting software are specifically designed for forest inventory. The specific software was developed to smoothly control the BEE scanner and to acquire the data, including the angular data, range data, and intensity data, and the data acquired by the BEE scanner could be processed into point cloud data, a range map, and an intensity map. Based on the point cloud data, the trees were detected by a single slice of the single scan in a plot, and the local ground plane was fitted for each detected tree. Then the diameter at breast height (DBH), tree height, and tree position could be estimated automatically by using the specific software. The experiments have been performed by using the BEE scanner in an artificial ginkgo forest which was located in the Haidian District of Beijing. Four 10 m × 10 m square plots were selected for the experiments. The BEE scanner scanned in the four plots and acquired the single-scan data, respectively. The DBH, tree height, and tree position of the trees in the four plots were estimated and analyzed. For comparison, manually-measured data was also collected in the four plots. The trunk detection rate for all four plots was 92.75%; the root mean square error of the DBH estimation was 1.27 cm; the root mean square error of the tree height estimation was 0.24 m; and the tree position estimation was in line with the actual position. The scanner also was tested in more natural forest in the JiuFeng Forest Park. Two plots with a radius of 5 meters were scanned. Eleven trees in the plot with a flat ground were detected and DBH were estimated. But tree detection was failed in the other plot because of the undulating ground. Experimental results show that the BEE scanner can efficiently estimate the structure parameters of plantation trees and has good potential in practical applications of forest inventory.

Highlights

Laser scanning is a surveying method which can measure the distance between the laser scanner and the point on the object illuminated by a laser
Terrestrial laser scanning (TLS) was used to collect the spatial information of the forest and measure the forest structure [9,10], and more and more experiments were carried out to estimate the attributes of trees, such as the diameter at breast height (DBH) [10,11], tree height [12], crown structure [13], leaf area index [14], and biomass [15], etc
This paper describes an automated low-cost 3D terrestrial laser scanner for measuring the DBH, tree height and tree position of the local plantation forest

Summary

Introduction

Laser scanning is a surveying method which can measure the distance between the laser scanner and the point on the object illuminated by a laser. In airborne and spaceborne laser scanning systems have been used to acquire the point cloud data of large areas of forest and create a forest inventory. The airborne and space-borne point cloud data, alone or integrated with other kinds of remote sensing data, like optical satellite image and SAR (synthetic aperture radar) images, are often used to characterize forest canopies [5], estimate the crown base height [6], estimate forest biomass [7], and capture tree crown formation [8]. Terrestrial laser scanning (TLS) is different from airborne and space-borne laser scanning. TLS data has the potential to perform the plot-level or tree-level forest inventory at very high precision. TLS was used to collect the spatial information of the forest and measure the forest structure [9,10], and more and more experiments were carried out to estimate the attributes of trees, such as the diameter at breast height (DBH) [10,11], tree height [12], crown structure [13], leaf area index [14], and biomass [15], etc

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