Random-Walker-Based Collaborative Learning for Hyperspectral Image Classification

Active learning (AL) and semisupervised learning (SSL) are both promising solutions to hyperspectral image classification. Given a few initial labeled samples, this work combines AL and SSL in a novel manner, aiming to obtain more manually labeled and pseudolabeled samples and use them together with the initial labeled samples to improve the classification performance. First, based on a comparison of the segmentation and spectral-spatial classification results obtained by random walker (RW) and extended RW (ERW) algorithms, the unlabeled samples are separated into two different sets, i.e., low- and high-confidence unlabeled data sets. For the high-confidence unlabeled data, pseudolabeling is performed, which can ensure the correctness and informativeness of the pseudolabeled samples. For the low-confidence unlabeled data, AL is used to select samples. In this way, the samples which are more effective for improvement of classification performance can be labeled in only a few iterations. Finally, with the learned training set and the original hyperspectral image as inputs, the ERW classifier is used to obtain the final classification result. Experiments performed on three real hyperspectral data sets show that the proposed method can achieve competitive classification accuracy even with a very limited number of manually labeled samples.