Tree Crown Analysis with Local Fractal Dimension Using an Aerial Image

Abstract

Forests play an important role in maintaining environmental conditions suitable for life on the earth. Forests have seasonal cycles and change from year to year. External factors such as harmful insects may cause damage, and the surrounding conditions are not constant. All these factors have an effect on the tree crown, therefore crown size measurement is an important task in forest management. The goal of this study was to measure the distribution of the tree crown size in the forest including closed canopies by image processing methods. We assumed that one crown consists of leaves and branches of similar color and that there are shadow areas around the crowns. Additionally each crown grows differently and has different structure. These features are used to identify a circular crown area. The size of a circle representing the crown is computed using the brightness distribution and local fractal dimension within the circular area. To measure the crown size distribution, forest was photographed from a helicopter, and the images were analyzed using the suggested technique. Comparing the analysis results and visual inspection of the same area, we concluded that the proposed technique was effective for measuring the crown size distribution.