A fast and Accurate Similarity-constrained Subspace Clustering Framework for Unsupervised Hyperspectral Image Classification

TL;DR

This paper introduces a fast, unsupervised subspace clustering framework that incorporates spatial information for hyperspectral image classification, significantly improving speed and accuracy over existing SSC methods.

Contribution

The paper proposes a novel, efficient algorithm that combines pixel neighborhood selection, spatial filtering, and spectral clustering to enhance land cover segmentation.

Findings

Achieves higher clustering accuracy than state-of-the-art SSC and deep learning methods.

Up to 1000 times faster than traditional SSC on large datasets.

Effective in producing spatially homogeneous segmentation results.

Abstract

Accurate land cover segmentation of spectral images is challenging and has drawn widespread attention in remote sensing due to its inherent complexity. Although significant efforts have been made for developing a variety of methods, most of them rely on supervised strategies. Subspace clustering methods, such as Sparse Subspace Clustering (SSC), have become a popular tool for unsupervised learning due to their high performance. However, the computational complexity of SSC methods prevents their use on large spectral remotely sensed datasets. Furthermore, since SSC ignores the spatial information in the spectral images, its discrimination capability is limited, hampering the clustering results' spatial homogeneity. To address these two relevant issues, in this paper, we propose a fast algorithm that obtains a sparse representation coefficient matrix by first selecting a small set of pixels that best represent their neighborhood. Then, it performs spatial filtering to enforce the connectivity of neighboring pixels and uses fast spectral clustering to get the final segmentation. Extensive simulations with our method demonstrate its effectiveness in land cover segmentation, obtaining remarkable high clustering performance compared with state-of-the-art SSC-based algorithms and even novel unsupervised-deep-learning-based methods. Besides, the proposed method is up to three orders of magnitude faster than SSC when clustering more than $2 \times 10^4$ spectral pixels.