Single-Species Detection With Airborne Imaging Spectroscopy Data: A Comparison of Support Vector Techniques

Progress in mapping plant species remotely with imaging spectroscopy data is limited by the traditional classification framework, which carries the requirement of exhaustively defining all classes (species) encountered in a landscape. As the research objective may be to map only one or a few species of interest, we need to explore alternative classification methods that may be used to more efficiently detect a single species. We compared the performance of three support vector machine (SVM) methods designed for single-class detection-binary (one-against-all) SVM, one-class SVM, and biased SVM-in detecting five focal tree and shrub species using data collected by the Carnegie Airborne Observatory over an African savanna. Prior to this comparison, we investigated the effects of training data amount and balance on binary SVM and evaluated alternative methods for tuning one-class and biased SVMs. A key finding was that biased SVM was generally best parameterized by crown-level cross validation paired with the tuning criterion proposed by Lee and Liu [1]. Among the different single-class methods, binary SVM showed the best overall performance (average F-scores 0.43-0.78 among species), whereas one-class SVM showed very poor performance (F-scores 0.09-0.46). However, biased SVM produced results similar to those obtained with binary SVM (F-scores 0.40-0.72), despite using labeled training data from only the focal class. Our results indicate that both binary and biased SVMs can work well for remote single-species detection, while both methods, particularly biased SVM, greatly reduce the amount of training data required compared with traditional multispecies classification.