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1. Detecting and Tracking Moving Airplanes from Space Based on Normalized Frame Difference Labeling and Improved Similarity Measures

   https://doi.org/10.3390/rs12213589  

   Shi, Fan ; Qiu, Fang ; Li, Xiao ; Zhong, Ruofei ; Yang, Cankun ; Tang, Yunwei ( November 2020 , Remote Sensing)

   null (Ed.)

   The emerging satellite videos provide the opportunity to detect moving objects and track their trajectories, which were not possible for remotely sensed imagery with limited temporal resolution. So far, most studies using satellite video data have been concentrated on traffic monitoring through detecting and tracking moving cars, whereas the studies on other moving objects such as airplanes are limited. In this paper, an integrated method for monitoring moving airplanes from a satellite video is proposed. First, we design a normalized frame difference labeling (NFDL) algorithm to detect moving airplanes, which adopts a non-recursive strategy to deliver stable detection throughout the whole video. Second, the template matching (TM) technique is utilized for tracking the detected moving airplanes in the frame sequence by improved similarity measures (ISMs) with better rotation invariance and model drift suppression ability. Template matching with improved similarity measures (TM-ISMs) is further implemented to handle the leave-the-scene problem. The developed method is tested on a satellite video to detect and track eleven moving airplanes. Our NFDL algorithm successfully detects all the moving airplanes with the highest F1 score of 0.88 among existing algorithms. The performance of TM-ISMs is compared with both its traditional counterparts and other state-of-the-art tracking algorithms. The experimental results show that TM-ISMs can handle both rotation and leave-the-scene problems. Moreover, TM-ISMs achieve a very high tracking accuracy of 0.921 and the highest tracking speed of 470.62 frames per second. 

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2. Center-Based 3D Object Detection and Tracking

   Yin, Tianwei ; Zhou, Xingyi ; Krähenbühl, Philipp ( June 2021 , IEEE Conference on Computer Vision and Pattern Recognition)

   null (Ed.)

   Three-dimensional objects are commonly represented as 3D boxes in a point-cloud. This representation mimics the well-studied image-based 2D bounding-box detection but comes with additional challenges. Objects in a 3D world do not follow any particular orientation, and box-based detectors have difficulties enumerating all orientations or fitting an axis-aligned bounding box to rotated objects. In this paper, we instead propose to represent, detect, and track 3D objects as points. Our framework, CenterPoint, first detects centers of objects using a keypoint detector and regresses to other attributes, including 3D size, 3D orientation, and velocity. In a second stage, it refines these estimates using additional point features on the object. In CenterPoint, 3D object tracking simplifies to greedy closest-point matching. The resulting detection and tracking algorithm is simple, efficient, and effective. CenterPoint achieved state-of-the-art performance on the nuScenes benchmark for both 3D detection and tracking, with 65.5 NDS and 63.8 AMOTA for a single model. On the Waymo Open Dataset, CenterPoint outperforms all previous single model methods by a large margin and ranks first among all Lidar-only submissions. 

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3. Automatic Displacement and Vibration Measurement in Laboratory Experiments with A Deep Learning Method

   Bai M., Abduallah R. ( November 2021 , IEEE SENSORS 2021 Conference)

   This paper proposes a pipeline to automatically track and measure displacement and vibration of structural specimens during laboratory experiments. The latest Mask Regional Convolutional Neural Network (Mask R-CNN) can locate the targets and monitor their movement from videos recorded by a stationary camera. To improve precision and remove the noise, techniques such as Scale-invariant Feature Transform (SIFT) and various filters for signal processing are included. Experiments on three small-scale reinforced concrete beams and a shaking table test are utilized to verify the proposed method. Results show that the proposed deep learning method can achieve the goal to automatically and precisely measure the motion of tested structural members during laboratory experiments. 

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4. Monitoring the earthquake response of full‐scale structures using UAV vision‐based techniques

   https://doi.org/10.1002/stc.2862  

   Wang, X ; Lo, E ; De Vivo, L ; Hutchinson, T ; Kuester, F ( January 2022 , Structural control health monitoring)

   Vision-based sensing, when utilized in conjunction with camera-equipped unmanned aerial vehicles (UAVs), has recently emerged as an effective sensing technique in a variety of civil engineering applications (e.g., construction monitoring, conditional assessment, and post-disaster reconnaissance). However, the use of these non-intrusive sensing techniques for extracting the dynamic response of structures has been restricted due to the perspective and scale distortions or image misalignments caused by the movement of the UAV and its on-board camera during flight operations. To overcome these limitations, a vision-based analysis methodology is proposed in the present study for extracting the dynamic response of structures using unmanned aerial vehicle (UAV) aerial videos. Importantly, geo-referenced targets were strategically placed on the structures and the background (stationary) region to enhance the robustness and accuracy related to image feature detection. Image processing and photogrammetric techniques are adopted in the analysis procedures first to recover the camera motion using the world-to-image correspondences of the background (stationary) targets and subsequently to extract the dynamic structural response by reprojecting the image feature of the (moving) targets attached to the structures to the world coordinates. The displacement tracking results are validated using the responses of two full-scale test structures measured by analog displacement sensors during a sequence of shake table tests. The high level of precision (less than 3 mm root-mean-square errors) of the vision-based structural displacement results demonstrates the effectiveness of the proposed UAV displacement tracking methodology. Additionally, the limitations and potential solutions associated with the proposed methodology for monitoring the dynamic responses of real structures are discussed. 

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5. Scale-invariant optical flow in tracking using a pan-tilt-zoom camera

   https://doi.org/10.1017/S0263574714002665  

   Dhou, Salam ; Motai, Yuichi ( September 2016 , Robotica)

   SUMMARY An efficient method for tracking a target using a single Pan-Tilt-Zoom (PTZ) camera is proposed. The proposed Scale-Invariant Optical Flow (SIOF) method estimates the motion of the target and rotates the camera accordingly to keep the target at the center of the image. Also, SIOF estimates the scale of the target and changes the focal length relatively to adjust the Field of View (FoV) and keep the target appear in the same size in all captured frames. SIOF is a feature-based tracking method. Feature points used are extracted and tracked using Optical Flow (OF) and Scale-Invariant Feature Transform (SIFT). They are combined in groups and used to achieve robust tracking. The feature points in these groups are used within a twist model to recover the 3D free motion of the target. The merits of this proposed method are (i) building an efficient scale-invariant tracking method that tracks the target and keep it in the FoV of the camera with the same size, and (ii) using tracking with prediction and correction to speed up the PTZ control and achieve smooth camera control. Experimental results were performed on online video streams and validated the efficiency of the proposed method SIOF, comparing with OF, SIFT, and other tracking methods. The proposed SIOF has around 36% less average tracking error and around 70% less tracking overshoot than OF. 

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