Hyperspectral Image Classification Using Attention-Based Bidirectional Long Short-Term Memory Network

Deep neural networks have been widely applied to hyperspectral image (HSI) classification areas, in which recurrent neural network (RNN) is one of the most typical networks. Most of the existing RNN-based classifiers treat the spectral signature of pixels as an ordered sequence, in which only unidirectional correlation along the wavelength direction of adjacent bands is considered. However, each band image is related to not only its preceding band images but also its successive band images. In order to fully explore such bidirectional spectral correlation within an HSI, in this article, a bidirectional long short-term memory (Bi-LSTM)-based network is designed for HSI classification. Moreover, a spatial-spectral attention mechanism is designed and implemented in the proposed Bi-LSTM network to emphasize the effective information and reduce the redundant information among spatial-spectral context of pixels, by which the performance of classification can be greatly improved. Experimental results over three benchmark HSIs, i.e., Salinas Valley, Pavia Centre, and Pavia University, demonstrate that our proposed Bi-LSTM obviously outperforms several state-of-the-art unidirectional RNN-based classification algorithms. Moreover, the proposed spatial-spectral attention mechanism can further improve the classification accuracy of our proposed Bi-LSTM algorithm by effectively weighting spatial and spectral context of pixels. The source code of the proposed Bi-LSTM algorithm is available at https://github.com/MeiShaohui/Attention-based-Bidirectional-LSTM-Network.