A New Individual Tree Crown Delineation Method for High Resolution Multispectral Imagery

Lin Qiu,Yunwei Tang,Hui Li,Linhai Jing,Baoxin Hu

doi:10.3390/rs12030585

Abstract

In current individual tree crown (ITC) delineation methods for high-resolution multispectral imagery, either a spectral band or a brightness component of the multispectral image is employed in delineation with reference to edges or shapes of crowns, whereas spectra of tree crowns are seldom taken into account. Such methods normally perform well in coniferous forests with obvious between-crown shadows, but fail in dense deciduous or mixed forests, in which tree crowns are close to each other, between-crown shadows and boundaries are unobvious, whereas adjacent tree crowns may be of distinguishable spectra. In order to effectively delineate crowns in dense deciduous or mixed forests, a new ITC delineation method using both brightness and spectra of the image is proposed in this study. In this method, a morphological gradient map of the image is first generated, treetops of multi-scale crowns are extracted from the gradient map and refined regarding the spectral differences between neighboring crowns, the gradient map is segmented using a watershed approach with treetops as markers, and the resulting segmentation map is refined to yield a crown map. Evaluated on images of a rainforest and a deciduous forest, the proposed method more accurately delineated adjacent broad-leaved tree crowns with similar brightness but different spectra than the other two typical ITC delineation algorithms, achieving a delineation accuracy of up to 76% in the rainforest and 63% in the deciduous forest.

Highlights

As one of the important targets for the management and protection of ecological resources, forests play an important role in soil and water conservation [1]
A morphological gradient map of the image is first generated, treetops of multi-scale crowns are extracted from the gradient map and refined regarding the spectral differences between neighboring crowns; the gradient map is segmented using a watershed approach with treetops as markers, and the resulting segmentation map is refined to yield a crown map
In order to evaluate the performances of the SMS method proposed, the traditional watershed segmentation method, the commonly used marker-controlled watershed segmentation (MWT) method, and the CSRIemmotee tShenos.d202w0,e12r,e58a5lso considered in the experiment

Summary

Introduction

As one of the important targets for the management and protection of ecological resources, forests play an important role in soil and water conservation [1]. Numerous ITC delineation methods using remote sensing data have been proposed, such as those based on valley following [10,11], between-tree shadow identification [12], region growing [13], edge detection [14,15], watershed segmentation [16], and three-dimensional (3-D) modeling [17]. These methods have been successfully applied in coniferous forests, but work poorly in dense deciduous and mixed forests with complicated structures [18,19,20,21]

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Conclusion