No abstract

Due to the limitations of imaging systems, the swath width of available hyperspectral images (HSIs) is relatively narrow, making it difficult to meet the demands of various applications. Therefore, an appealing idea is to expand the width of HSIs by using widely covered multispectral images (MSIs), called spectral super-resolution (SSR) of MSIs. According to the radiation transmission process of the imaging system, the spectral mixing characteristics of ground objects can be described by the linear spectral mixing model (LSMM). Inspired by the linear mixed part and nonlinear residual part of the LSMM, we propose a double-branch SSR network. To generate wide HSIs, a spectral mixing branch is designed to extract abundances from wide MSIs and adaptively learn hyperspectral endmembers from narrow HSIs. Furthermore, considering the nonlinear factors in the imaging system and atmospheric transmission, a nonlinear residual branch is built to complement the spectral and spatial details. Finally, the SSR result can be obtained with the fusion of linear and nonlinear features. To make the network structure achieve corresponding physical significance, we constrain the network through joint loss functions at different stages. In addition to two simulated datasets with limited coverage, our model is also evaluated on a real MSI–HSI dataset in a larger area. Extensive experiments show the superiority of the proposed model compared with state-of-the-art baselines. Moreover, we visualized the internal results of our network and conducted ablation experiments on a single branch to further demonstrate its effectiveness. In the end, the influence of network hyperparameters, including endmembers and loss function weight coefficient, is discussed and analyzed in detail.

In recent years, the development of super-resolution (SR) algorithms based on convolutional neural networks has become an important topic in enhancing the resolution of multi-channel remote sensing images. However, most of the existing SR models suffer from the insufficient utilization of spectral information, limiting their SR performance. Here, we derive a novel hybrid SR network (HSRN) which facilitates the acquisition of joint spatial–spectral information to enhance the spatial resolution of multi-channel remote sensing images. The main contributions of this paper are three-fold: (1) in order to sufficiently extract the spatial–spectral information of multi-channel remote sensing images, we designed a hybrid three-dimensional (3D) and two-dimensional (2D) convolution module which can distill the nonlinear spectral and spatial information simultaneously; (2) to enhance the discriminative learning ability, we designed the attention structure, including channel attention, before the upsampling block and spatial attention after the upsampling block, to weigh and rescale the spectral and spatial features; and (3) to acquire fine quality and clear texture for reconstructed SR images, we introduced a multi-scale structural similarity index into our loss function to constrain the HSRN model. The qualitative and quantitative comparisons were carried out in comparison with other SR methods on public remote sensing datasets. It is demonstrated that our HSRN outperforms state-of-the-art methods on multi-channel remote sensing images.

Hyperspectral images (HSIs) with abundant spectral information are generally susceptible to various types of noise, such as Gaussian noise and stripe noise. Recently, a few quality-based selection algorithms have been proposed to remove noise bands from HSIs. However, these methods suffer from an inability to discriminate the mixed-noise bands of HSIs and are sensitive to image content variation and luminance changes. Here, we develop a mixed-noise band selection framework that can separate the Gaussian and stripe noise bands from HSIs effectively. We first improve tensor decomposition to reconstruct the mixed-noise components and low-rank components, which reduces the influence of image content and luminance changes. Spectral smoothness constraints and unidirectional total variation are incorporated into the decomposition model to enhance the separation performance for Gaussian and stripe noise. Then, different statistical features, including Weibull and histogram of oriented gradient (HOG) features, are applied to extract the robust parameters from mixed-noise components. More importantly, an extreme learning machine (ELM) is trained to predict the noise bands. The ELM has an extremely fast learning speed and tends to achieve better performance than other networks. Finally, by aggregating all these strategies, our methods can select the mixed-noise bands efficiently. The experimental results on both synthetic and real noise HSIs indicate that the proposed method outperforms the state-of-the-art methods.