Detecting vulnerable road users (VRUs) at night presents significant challenges. Numerous methods rely heavily on annotations, yet the low visibility of nighttime images poses difficulties for labeling. To obviate the need for nighttime annotations, unsupervised domain adaptation manifests as a viable solution. However, existing approaches primarily focus on semantic-level domain gaps, often overlooking pixel-level discrepancies caused by inherent degradations in the nighttime domain. These degradations can impair machine vision and limit detection performance. In this paper, we propose TripleA, an unsupervised domain adaptation framework tailored for nighttime VRU detection. TripleA includes triple alignment. First, it aligns daytime and nighttime images to generate synthetic nighttime images, which are then enhanced for illumination and noise. To remove noise, we introduce an illumination difference-aware denoising network, incorporating a novel pseudo-supervised attention to achieve pixel-wise noise distribution alignment. This alignment is driven by pseudo-ground truth generated through a carefully designed exchange-recombination strategy, facilitating self-supervised training of the denoising network. Additionally, we introduce degradation alignment to ensure domain-invariant degradation encoding, which enhances the network’s robustness for real-world nighttime images. Extensive experiments demonstrate the effectiveness of our framework for nighttime VRU detection, all without the need for annotated nighttime data.

Pan-sharpening is a technique used to create high-resolution multispectral (HRMS) images by merging low-resolution multispectral (LRMS) images with corresponding high-resolution panchromatic (PAN) images. Despite achieving state-of-the-art performance, existing panchromatic sharpening networks based on deep-learning (DL) methods suffer from spectral distortion and insufficient spatial texture enhancement. To address this challenge, this letter introduces a novel cross-spectral–spatial fusion network (CSSFN) for pan-sharpening remote sensing images. The network utilizes a cross-spectral–spatial attention block (CSSAB) to extract both the spectral information of the MS branch and the spatial information of the PAN branch. The spectral and spatial feature representations of remote sensing images are then progressively enhanced, which improves the fusion process and generates multispectral images with high spatial resolution. Our network outperforms other pan-sharpening methods on two publicly available datasets, as demonstrated by extensive experiments, yielding state-of-the-art results.

The rapid development and commercialization of Unmanned Aerial Vehicle (UAV) technology has made it possible to conduct urban traffic information extraction using UAV images. However, the large variations of targets in urban environments, complex foregrounds and backgrounds in cities, and severe tree and shadow occlusions pose great challenges in car and road extraction using UAV images. In this study, we propose a lightweight, Efficient Dual Contextual Parsing Network (EDCPNet) to address the above issues. The proposed EDCP module in EDCPNet is mainly composed of spatial contextual parsing (SCP) and channel contextual parsing (CCP), which can effectively acquire rich contextual features in both spatial and channel dimensions, adaptively recalibrate the attention weights, perceive the salient features of targets in images, and suppress the importance of irrelevant elements. It thus leads to improved performance and adaptability that facilitate the practical applications of large-scale urban traffic monitoring in complex urban scenes. We conduct experiments on two benchmark datasets (UAVid and UDD) by comparing the proposed EDCPNet with six other competing methods, i.e., U-Net, PSPNet, Deelabv3+, SegNet, ESNet, and ERFNet, and validate the effectiveness of the proposed EDCP module via extensive ablation studies. The results suggest that the proposed network outperforms all competing methods in car and road extraction from UAV images with a balanced computational cost. Its great performance and low computational demand (with only 2.37M model parameters) facilitate its deployment on edge computing devices with memory constraints.

The goal of pan-sharpening tasks is to fuse panchromatic (PAN) images and low-spatial-resolution (LR) multispectral (MS) images for the purpose of aggregating texture and spectral information. Although traditional embedding-based pan-sharpening methods achieve competitive results, they are limited by the shallow network and not suitable for large-scale datasets. In this study, we design a novel multiscale locally linear embedding residual network (LLERN) that consists of two phases: the spectral preservation phase and the structural preservation phase. As the pretreatment of the structural preservation network, the spectral preservation network aims to upscale the LR MS image while retaining spectral information. The proposed locally linear embedding residual block (LLERB) in the structural preservation phase can search for similar sparse patches from the PAN image space and embed the corresponding local geometric relationship into the residual space to enhance the MS image. Extensive experiments suggest that the proposed LLERN outperforms state-of-the-art methods from visual and quantitative perspectives, and confirm the assumption that LR image patches and residual image patches in a local region share a similar manifold structure, which can be used to guide deep-learning modeling with improved interpretability. The source code is available athttps://github.com/jiaming-wang/LLERN.

Coronavirus Disease 2019 (COVID-19) is a highly infectious virus that has created a health crisis for people all over the world. Social distancing has proved to be an effective non-pharmaceutical measure to slow down the spread of COVID-19. As unmanned aerial vehicle (UAV) is a flexible mobile platform, it is a promising option to use UAV for social distance monitoring. Therefore, we propose a lightweight pedestrian detection network to accurately detect pedestrians by human head detection in real-time and then calculate the social distancing between pedestrians on UAV images. In particular, our network follows the PeleeNet as backbone and further incorporates the multi-scale features and spatial attention to enhance the features of small objects, like human heads. The experimental results on Merge-Head dataset show that our method achieves 92.22% AP (average precision) and 76 FPS (frames per second), outperforming YOLOv3 models and SSD models and enabling real-time detection in actual applications. The ablation experiments also indicate that multi-scale feature and spatial attention significantly contribute the performance of pedestrian detection. The test results on UAV-Head dataset show that our method can also achieve high precision pedestrian detection on UAV images with 88.5% AP and 75 FPS. In addition, we have conducted a precision calibration test to obtain the transformation matrix from images (vertical images and tilted images) to real-world coordinate. Based on the accurate pedestrian detection and the transformation matrix, the social distancing monitoring between individuals is reliably achieved.