Spectral Angle-Based Feature Extraction and Sparse Representation-Based Classification of Hyperspectral Imagery
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Remote sensing involves measuring and analyzing objects of interests through data collected by a remote imaging modality without physical contact with the objects. Hyperspectral sensors have become increasingly popular for a variety of remote sensing applications. Hyperspectral data are composed of densely sampled reflectance values over a wide range of the electromagnetic spectrum. Such a wealth of spectral information can provide unique spectral signatures of different materials present in a scene, which makes it especially suitable for classification tasks. In this dissertation, we present new dimensionality reduction (feature extraction) and classification algorithms for high-dimensional hyperspectral data. Specifically, we develop the theory and validate a new dimensionality reduction approach that maximizes angular separation in the lower dimensional subspace. We also propose and develop its ``local'' and ``nonlinear kernel'' variants for robust feature extraction of hyperspectral data. By preserving angular properties, the resulting subspaces demonstrate robustness to a variety of sources of variability that are commonly encountered in remote sensing applications. We also extend this approach to its ``spatial variant'' by incorporating spatial-contextual information along with spectral information from the hyperspectral images. We also optimize and develop a suitable sparse representation based classification framework for hyperspectral images. By extensive experiments on several real-world hyperspectral datasets, we demonstrate that the proposed algorithms significantly outperform the state-of-the-art methods. Further, we also demonstrate the applicability of the proposed methods for a practical environmental remote sensing task.