Three Dimensional Map Building for Forest Structure Analysis Using a Small-sized Laser Scanner Keiko Shiozawa*/**** , Toshihiko Mochizuki */****, Shuhei Kondou*/**** , Takashi Tsubouchi** , Asuka Asano** , Mitsuhiro Matsumoto*** , Shuhei Tomimura* , Shuichi Nakanishi* , Akiko Mochizuki* , Kouji Sasaki**** , Tohru Hayami* * Forest Revitalization System Corp. , ** Tsukuba Univ. , *** Kurume National College of Technology ,**** AdIn Research, Inc.

A portable laser scanning equipment and data processing software for measuring forest structure are developed. It will contribute to introducing Information Technologies (IT) into forestry field where manual measurements have been carried out so far. The equipment consists of a small-sized laser scanner and a rotating mechanism for the scanner. 3D point clouds which are a set of points between the scanner and measured coordinates on the scanned surface of stems, leaves, branches and forest floor are obtained by rotating the scanner at several measuring locations. The point clouds are processed to reconstruct 3D map and tree sizes such as DBH, Height , etc., which are necessary for forest management are extracted. As scanning depth is limited, every scanned data for different measuring location must be integrated in one large map. An algorithm for the integration is developed based on the iterative closest point (ICP) algorithm. After the integration, tree trunk cross-section was approximated as a circle by least square method and then stem diameter can be estimated at breast height.

Abstract

Background and Purpose 3D Map

・Importance of forest structure measurement ・Requirement of measuring accurate forest biomass. ・Sustainable wood resource supply and global environmental protection. ・Issues ・Currently manual measurements using tape and caliper, etc. ・Variability of measurement data caused by the skill of measurements. ・Effects and Impacts ・Measurements by small portable equipment. ・Applying robot technology such as SLAM (Simultaneous Localization and Mapping) to forest structure measurement. ・Using a small, light and cheap laser scanner.

Purpose ・Three dimensional map building and data extraction of forest trees.

・Less than 10kg weight of the equipment for portable/practical use. ・Measurement error of DBH =< 2cm and location =< 10cm.

Forest picture Measuring equipment 3D map

Experiment

Measurement was carried out with the developed one

legged equipment in the Japanese cypress forest.

PC

A small sized laser

scanner

(Hokuyo UTM-30LX)

Experimental equipment and measurement scene

An example of integrated 3D Map of trees in the forest

Point Clouds at Each Measured Location

Measurement data at location 1 Measurement data at location 2 Measurement data at location 3 Measurement data at location 4 Measurement data at location 5

Every set of the scanned data at different measured location is integrated in one large 3D map. An algorithm for the integration is developed based on the iterative closest point (ICP) algorithm which is one of SLAM methods.

Tree Sizes Extraction

Location and DBH are obtained by fitting a circle to every tree of breast height and by least square method.

Location of measurement equipment and trees

22errorlocationyerrorlocationxerrorlocation

Conclusions

1. Useful: New reconstruction methodology for 3D map of forest trees and their sizes extraction

2. Proved: Possible to measure tree diameter and contribution to obtaining the timber volume in the forest

3. Proved: Contribution to some applications such as simulated forest thinning using relative position of trees obtained

Comparison calculated location & breast-height diameter with manual measurement data

Goal

Background