in the field of spatial-spectral fusion, the modelbased method and the deep learning (DL)-based method are state-of-the-art. This paper presents a fusion method that incorporates the deep neural network into the model -based method for the most common case in the spatial-spectral fusion: PAN/multispectral (MS ) fusion. S pecifically, we first map the gradient of the high spatial resolution panchromatic image (HR-PAN) and the low spatial resolution multispectral image (LR-MS ) to the gradient of the high spatial resolution multispectral image (HR-MS ) via a deep residual convolutional neural network (CNN). Then we construct a fusion framework by the LR-MS image, the gradient prior learned from the gradient network, and the ideal fused image. Finally, an iterative optimization algorithm is used to solve the fusion model. Both quantitative and visual assessments on high-quality images from various sources demonstrate that the proposed fusion method is superior to all the mainstream algorithms included in the comparison in terms of overall fusion accuracy.
Urban geographical maps are important to urban planning, urban construction, land-use studies, disaster control and relief, touring and sightseeing, and so on. Satellite remote sensing images are the most important data source for urban geographical maps. However, for optical satellite remote sensing images with high spatial resolution, certain inevitable factors, including cloud, haze, and cloud shadow, severely degrade the image quality. Moreover, the geometrical and radiometric differences amongst multiple high-spatial-resolution images are difficult to eliminate. In this study, we propose a robust and efficient procedure for generating high-resolution and high-quality seamless satellite imagery for large-scale urban regions. This procedure consists of image registration, cloud detection, thin/thick cloud removal, pansharpening, and mosaicking processes. Methodologically, a spatially adaptive method considering the variation of atmospheric scattering, and a stepwise replacement method based on local moment matching are proposed for removing thin and thick clouds, respectively. The effectiveness is demonstrated by a successful case of generating a 0.91-m-resolution image of the main city zone in Nanning, Guangxi Zhuang Autonomous Region, China, using images obtained from the Chinese Beijing-2 and Gaofen-2 high-resolution satellites.
Hyperspectral image (HSI) fusion can effectively improve the spatial resolution of HSIs by integrating high resolution multispectral images (MSIs). Considering the spatial and spectral degradation relationship between a fused image and input images, a physics-based GAN is proposed to fuse HSI and MSI. A physical model estimating degradation of image is introduced in the generator and in the discriminators. For the generator, a set of recursive modules including a physical degradation model and a multiscale residual channel attention fusion module (MRCAFM) integrate the spectral-spatial difference information between input images and estimated degradation images to restore the details of the fused image. Subsequently, the residual spatial attention fusion module is used to combine the results of all recursions to obtain the final reconstructed result. As for the discriminators, three networks with the final fused image, estimated LR HSI and estimated MSI as inputs share the same architecture. Finally, the loss function that contains adversarial losses and L1 losses of the fused image and estimated degradation images is used to optimize network parameters. The experimental results demonstrate that the proposed method outperforms state-of-the-art methods.
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