Detection of Hedges in a Rural Landscape Using a Local Orientation Feature: From Linear Opening to Path Opening

Abstract

The detection of hedges is addressed in this paper. A hierarchical detection scheme in two steps is proposed. It is based on the use of both spatial information and spectral information in the detection process. First, woody elements are detected using the spectral information. From the membership map, the local orientation of each pixel is computed using directional filters. The morphological directional profile is defined as the composition of the outputs of directional filters with a varying orientation parameter. The local orientation feature is defined as the difference between the maximum and the minimum values of the morphological directional profile. A second detection step is done using the local orientation feature and the membership value to the woody elements class to extract the hedges. Experiments conducted on several real satellite images show that the method provides very good results in terms of detection accuracies. For one experiment, the overall accuracy is increased 80% to 91% with the proposed method. Furthermore, the methods is robust even if the size of the training samples is limited.