End-to-End Convolutional Network and Spectral-Spatial Transformer Architecture for Hyperspectral Image Classification

Abstract

Although convolutional neural networks (CNNs) have proven successful for hyperspectral image classification (HSIC), it is difficult to characterize the global dependencies between HSI pixels at long-distance ranges and spectral bands due to their limited receptive domain. The transformer can compensate well for this shortcoming, but it suffers from a lack of image-specific inductive biases (i.e., localization and translation equivariance) and contextual position information compared with CNNs. To overcome the aforementioned challenges, we introduce a simply structured, end-to-end convolutional network and spectral–spatial transformer (CNSST) architecture for HSIC. Our CNSST architecture consists of two essential components: a simple 3D-CNN-based hierarchical feature fusion network and a spectral–spatial transformer that introduces inductive bias information. The former employs a 3D-CNN-based hierarchical feature fusion structure to establish the correlation between spectral and spatial (SAS) information while capturing richer inductive bias and more discriminative local spectral-spatial hierarchical feature information, while the latter aims to establish the global dependency among HSI pixels while enhancing the acquisition of local information by introducing inductive bias information. Specifically, the spectral and inductive bias information is incorporated into the transformer’s multi-head self-attention mechanism (MHSA), thus making the attention spectrally aware and location-aware. Furthermore, a Lion optimizer is exploited to boost the classification performance of our newly developed CNSST. Substantial experiments conducted on three publicly accessible hyperspectral datasets unequivocally showcase that our proposed CNSST outperforms other state-of-the-art approaches.

Keywords

• convolutional neural networks (CNNs)
• hyperspectral image classification (HSIC)
• spectral–spatial transformer
• multi-head self-attention (MHSA)