Individual Tree-Crown Delineation and Treetop Detection in High-Spatial-Resolution Aerial Imagery

Abstract

The cost of forest sampling can be reduced substantially by the ability to estimate forest and tree parameters directly from aerial photographs. However, in order to do so it is necessary to be able to accurately identify individual treetops and then to define the region in the vicinity of the treetop that encompasses the crown extent. These two steps commonly have been treated independently. In this paper, we derive individual tree-crown boundaries and treetop locations under a unified framework. We applied a two-stage approach with edge detection followed by markercontrolled watershed segmentation. A Laplacian of Gaussian edge detection method at the smallest effective scale was employed to mask out the background. An eight-connectivity scheme was used to label the remaining tree objects in the edge map. Subsequently, treetops are modeled based on both radiometry and geometry. More specifically, treetops are assumed to be represented by local radiation maxima and also to be located near the center of the tree-crown. As a result, a marker image was created from the derived treetop to guide a watershed segmentation to further differentiate touching and clumping trees and to produce a segmented image comprised of individual tree crowns. Our methods were developed on a 256-by 256-pixel CASI image of a commercially thinned trial forest. A promising agreement between our automatic methods and manual delineation results was achieved in counting the number of trees as well as in delineating tree crowns.

Interpretation of Forest Resources at the Individual Tree Level at Purple Mountain, Nanjing City, China, Using WorldView-2 Imagery by Combining GPS, RS and GIS Technologies

“…These satellites can obtain imagery at low cost for several areas simultaneously with a very high resolution of 1 m or less in panchromatic mode, enabling the measurement of forest resources at the individual tree level by satellite remote sensing and computer technology [14][15][16]. In recent years, the damaged ecological environment of China has required forest conservation instead of wood harvest.…”

Application of high-resolution airborne data using individual tree crowns in Japanese conifer plantations

“…The double-aspect method was developed by Walsworth and King (1999), who used the technique to identify aspen tree apices in black and white archival aerial photographs. The watershed method (Wang et al 2004) is an improvement on the double-aspect method. It consists of inverting image brightness, and then applying a flooding model based on a growing region that treats crown apices as seeds (Erikson 2003, Lamar et al 2005, Pouliot and King 2005.…”

Improving the Precision of Tree Counting by Combining Tree Detection with Crown Delineation and Classification on Homogeneity Guided Smoothed High Resolution (50 cm) Multispectral Airborne Digital Data

“…There are some improved approaches for individual tree crown detection and delineation [21][22][23] and tree counting by species could attain higher accuracy by combining with these methods. Further application and testing are needed to extend our results to larger areas, multiple scenes, varied topographies and different forest conditions.…”