Detailed reconstruction of trees from terrestrial laser scans for remote sensing and radiative transfer modelling applications

Růžena Janoutová,Jan Novotný,Miroslav Pikl,Barbora Navrátilová,Lucie Homolová,Zbyněk Malenovský,Stephen P Long,Katrin Kahlen

doi:10.1093/insilicoplants/diab026

Abstract

AbstractThis study presents a method for three-dimensional (3D) reconstruction of forest tree species that are, for instance, required for simulations of 3D canopies in radiative transfer modelling. We selected three forest species of different architecture: Norway spruce (Picea abies) and European beech (Fagus sylvatica), representatives of European production forests, and white peppermint (Eucalyptus pulchella), a common forest species of Tasmania. Each species has a specific crown structure and foliage distribution. Our algorithm for 3D model construction of a single tree is based on terrestrial laser scanning (TLS) and ancillary field measurements of leaf angle distribution, percentage of current-year and older leaves, and other parameters that could not be derived from TLS data. The algorithm comprises four main steps: (i) segmentation of a TLS tree point cloud separating wooden parts from foliage, (ii) reconstruction of wooden parts (trunks and branches) from TLS data, (iii) biologically genuine distribution of foliage within the tree crown and (iv) separation of foliage into two age categories (for spruce trees only). The reconstructed 3D models of the tree species were used to build virtual forest scenes in the Discrete Anisotropic Radiative Transfer model and to simulate canopy optical signals, specifically: angularly anisotropic top-of-canopy reflectance (for retrieval of leaf biochemical compounds from nadir canopy reflectance signatures captured in airborne imaging spectroscopy data) and solar-induced chlorophyll fluorescence signal (for experimentally unfeasible sensitivity analyses).

Highlights

Three study sites were used for collecting terrestrial laser scanning (TLS) data: Černá hora in the Czech Republic for Norway spruce; Hobart in Tasmania, Australia for white peppermint; and Těšínské Beskydy in the Czech Republic for European beech
In Appendices A and B, we provide two case studies as examples demonstrating use of the 3D tree representations created in this work for (i) interpretation of airborne and space-borne spectral RS data and (ii) investigating influence of forest structures, woody components, on remotely sensed SIF signal
The reconstruction proved to be robust and applicable to the three species of this study, it requires further testing, especially for tree species of irregular shapes growing in extreme environmental conditions

Summary

Introduction

Bílý Kříž and Štítná, both in the Czech Republic, were used to collect supporting data, such as leaf optical, biochemical and other structural properties. Each of the latter is a part of a permanent experimental research network created around an eddy-covariance flux measuring tower. Their permanency resulted in collecting a large amount of continuous measurements during several multi-scale field campaigns, which serve as the source of data for our study.

Objectives

Methods

Findings

Conclusion