With the resolution improvement of the remote-sensing images, more details are shown clearly. The challenge that comes along is how to boost the relatively low classification accuracy caused by using pixel-based image classification approaches and low-level visual structure. The low-level features (LLF) may not well describe the image due to the semantic gap between low-level visual features and high-level semantics of images. The bag-of-visual-words (BOV) model which generates mid-level features was proposed to bridge the two levels. However, it generally neglects the context information between local patches. In this paper, an object-oriented semantic classification algorithm that combines BOV with the optimal segmentation scale is presented. In this algorithm, BOV addresses the problem of the representation of mid-level for scenes, while the optimal segmentation scale intends to overcome the defect of conventional BOV in lacking of relationship between image patches and to give more thorough description. The object-based BOV is presented to construct mid-level representations for object description instead of LLF, and histogram intersection kernel (HIK) is introduced in support vector machine (SVM) for classification. The experiments conducted on three datasets testify the superiority of the proposed algorithm.

Owing to the limits of incident energy and hardware system, hyperspectral (HS) images always suffer from low spatial resolution, compared with multispectral (MS) or panchromatic (PAN) images. Therefore, image fusion has emerged as a useful technology that is able to combine the characteristics of high spectral and spatial resolutions of HS and PAN/MS images. In this paper, a novel HS and PAN image fusion method based on convolutional neural network (CNN) is proposed. The proposed method incorporates the ideas of both hyper-sharpening and MS pan-sharpening techniques, thereby employing a two-stage cascaded CNN to reconstruct the anticipated high-resolution HS image. Technically, the proposed CNN architecture consists of two sub-networks, the detail injection sub-network and unmixing sub-network. The former aims at producing a latent high-resolution MS image, whereas the latter estimates the desired high-resolution abundance maps by exploring the spatial and spectral information of both HS and MS images. Moreover, two model-training fashions are presented in this paper for the sake of effectively training our network. Experiments on simulated and real remote sensing data demonstrate that the proposed method can improve the spatial resolution and spectral fidelity of HS image, and achieve better performance than some state-of-the-art HS pan-sharpening algorithms.

A decision-level-based synergetic classification method has been proposed to conduct land-cover classification for long-wave infrared (LWIR) and high-resolution visible (VIS) images in this paper. The problem of synergic classification is challenging, since we aim for classification map at the spatial resolution of the VIS image under different imaging modes. The proposed method consists of two stages, i.e., stage of classifications for LWIR hyperspectral (HS) and VIS images separately, and stage of decision-level fusion for both classification results. For LWIR HS image, we have proposed a new semisupervised feature extraction method named as semisupervised local discriminant analysis (SLDA) for SVM classification. In parallel, spatial features which have been extracted from the high-resolution VIS image are used to combine with the spectral features for classification. In the second stage, several common decision-level fusion rules have been employed to integrate both classification results. We also present a context-based opinion pools (CBP) strategy to enhance the classification accuracy. Experiments conducted on the dataset of 2014 IEEE GRSS Data Fusion Contest show the advantage of our proposed SLDA method for HS image, and the effect of spatial-spectral features for high-resolution VIS image. Especially, the presented synergic classification strategy for HS and VIS images has higher overall accuracy and better visual effect than those only using single source image and those compared fusion methods in the experiments.

Region-of-interest (ROI) detection techniques are of great importance in the analysis of remote sensing images, especially in target detection, since the size of the image to be dealt with grows substantially with the improvement of spatial resolution. Most of current studies are not aiming at the specific type of object area detection, and the processed images are rather small compared to the size of the raw data acquired by high-resolution satellite. In this letter, a hierarchical task-driven ROI detection method, based on saliency and density, is proposed to address the detection of the potential object areas in large-scale remote sensing images. The proposed saliency and density-based detection method (SDBD) integrates bottom-up and top-down strategies, where the saliency-based multilevel histogram contrast is presented in the bottom-up phase to obtain the preliminary regions, while the centroid density distribution index (CDDI) is defined in the top-down scheme to refine the previous results. Specifically, superpixel segmentation is introduced in this letter to narrow down the ROI candidates. SDBD is capable of extracting ROI of different objects by adjusting the threshold of CDDI. The experiments are conducted on two data sets to extract ROIs of storage tanks and residence. Experimental results demonstrate that the proposed method is effective in identifying ROI in large-scale data.

With the development of autonomous driving and the emergence of various intelligent traffic scenarios, object detection technology based on deep learning is more and more widely applied to real traffic scenarios. Commonly used detection devices include LiDAR and cameras. Since the implementation of traffic scene target detection technology requires mass production, the advantages of millimeter-wave radar have emerged, such as low cost and no interference from the external environment. The performance of LiDAR and cameras is greatly reduced due to their sensitivity to light, which affects target detection at night and in bad weather. However, millimeter-wave radar can overcome the influence of these harsh environments and has a great auxiliary effect on safe driving on the road. In this work, we propose a deep-learning-based object detection method considering the radar range–Doppler spectrum in traffic scenarios. The algorithm uses YOLOv8 as the basic architecture, makes full use of the time series characteristics of range–Doppler spectrum data in traffic scenarios, introduces the ConvLSTM network, and exerts the ability to process time series data. In order to improve the model’s ability to detect small objects, an efficient and lightweight Efficient Channel Attention (ECA) module is introduced. Through extensive experiments, our model shows better performance on two publicly available radar datasets, CARRADA and RADDet, compared to other state-of-the-art methods. Compared with other mainstream methods that can only achieve 30–60% mAP performance when the IOU is 0.3, our model can achieve 74.51% and 75.62% on the RADDet and CARRADA datasets, respectively, and has better robustness and generalization ability.

In this paper, we propose a self-learning approach for remote sensing image classification. The main work of this paper aims at providing a new framework of semisupervised learning technique for multiple-source synergetic classification, thereby improving the classification accuracy under the condition of small samples. Considering the high spectral resolution of a hyperspectral (HS) image and the high spatial resolution of a panchromatic (PAN) image, the proposed approach combines image segmentation with an active learning algorithm and adopts a standard active learning method for a self-learning strategy, in which the learning algorithm automatically selects informative unlabeled samples by itself according to their collaborative spatial-spectral features and the predicted information of a spectral-based classifier. This way, no extra cost of human expertise is required for labeling the selected pixels when compared with conventional active learning methods. Experiments on three data sets, including HS and PAN images, indicate that our proposed approach has a great enhancement on overall classification accuracy compared with classical supervised algorithms and turns out to be a promising strategy in synergetic classification of HS and PAN images.