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Correct object detection plays a key role in generating an accurate object tracking result. Feature-based methods have the capability of handling the critical process of extracting features of an object. This paper aims to investigate object tracking using feature-based methods in terms of (1) identifying and analyzing the existing methods; (2) reporting and scrutinizing the evaluation performance matrices and their implementation usage in measuring the effectiveness of object tracking and detection; (3) revealing and investigating the challenges that affect the accuracy performance of identified tracking methods; (4) measuring the effectiveness of identified methods in terms of revealing to what extent the challenges can impact the accuracy and precision performance based on the evaluation performance matrices reported; and (5) presenting the potential future directions for improvement. The review process of this research was conducted based on standard systematic literature review (SLR) guidelines by Kitchenam's and Charters'. Initially, 157 prospective studies were identified. Through a rigorous study selection strategy, 32 relevant studies were selected to address the listed research questions. Thirty-two methods were identified and analyzed in terms of their aims, introduced improvements, and results achieved, along with presenting a new outlook on the classification of identified methods based on the feature-based method used in detection and tracking process. [ABSTRACT FROM AUTHOR]

Infrared target tracking technology is one of the core technologies in infrared imaging guidance systems and is also a hot research topic. The problem of particle degradation could be always found in traditional particle filtering, and a large number of particles are additionally required for accurate estimation. It is difficult to meet the requirements of a modern infrared imaging guidance system for accurate target tracking. To solve the problem of particle degradation and improve the performance of infrared target tracking, the extended Kalman filter and genetic algorithm are introduced into particle filtering, and an improved algorithm for infrared target tracking is proposed in this paper. In the framework of a particle filter algorithm, the Gaussian distribution for each particle is generated and propagated by a separate extended Kalman filter to improve the sampling accuracy and effectiveness of the probability density function of particles. Genetic algorithm is used to perform a resampling process to solve particle degradation and ensure the diversity of particle states in particle swarm. Simulation results show that the improved tracking algorithm based on improved particle filtering proposed in this paper can effectively solve the phenomenon of particle degradation and track the infrared target. [ABSTRACT FROM AUTHOR]

In this paper, we target the "precision visual tracking" problem, which is the precise tracking of a target point on a moving object. Compared with the abundant efforts in object-level tracking, which aims at accurately predicting the bounding box (or the mask) of the object, much less attention has been drawn to precision visual tracking. To this end, we present a template tracking framework that consists of two parts, template matching and template updating. For template matching, we trained a deep architecture to directly estimate the projective transformation that deforms the template to the search image. For template updating, we came up with a systematic strategy to update the initial and new templates. To avoid drift build-ups, we incorporate a fast-running dense correspondence matching module into the template update step. The proposed method was extensively tested on both synthetic and real data. To generate the synthetic data, we created a dataset of 480 image sequences. Each image sequence comes with the trajectory ground truth of a target point moving across all the frames. We compared the proposed method with six comparative approaches on this dataset. The tracking accuracy achieved by the proposed method was as follows: around 44% of the tracking errors were less than one pixel, about 78% of them were less than three pixels, and only about 14% of them exceeded five pixels. The proposed method is fast, running at 14 frames-per-second (fps) on 9 6 0 × 5 4 0 image sequences on a workstation equipped with a Nvidia RTX 2080Ti graphic card. Qualitative results also show that the proposed method is applicable to real-world image sequences. The related code, pre-trained models, and the test data will be made publicly available at https://github.com/XM-Peng/Precision-Visual-Tracking/. [ABSTRACT FROM AUTHOR]

Moving object detection and tracking have various applications, including surveillance, anomaly detection, vehicle navigation, etc. The literature on object detection and tracking is rich enough, and there exist several essential survey papers. However, the research on camouflage object detection and tracking is limited due to the complexity of the problem. Existing work on this problem has been done based on either biological characteristics of the camouflaged objects or computer vision techniques. In this paper, we review the existing camouflaged object detection and tracking techniques using computer vision algorithms from the theoretical point of view. This paper also addresses several issues of interest as well as future research direction in this area. We hope this paper will help the reader to learn the recent advances in camouflaged object detection and tracking. [ABSTRACT FROM AUTHOR]

Aiming at problems such as tracking failure caused by illumination changes often encountered during unmanned aerial vehicle (UAV) tracking, a target tracking algorithm with illumination adaptive and future-aware correlation filters is proposed based on the background-aware correlation filters (BACF) algorithm, which realizes reliable UAV tracking tasks at night. First, the dark scene is recognized, and an efficient image enhancement module is used to enhance the brightness of low illumination images. Then a future-aware module is constructed to train the tracking model using the contextual information of the target in the next frame for better robustness. Finally, the model updating stage involves adaptive filter updating and adaptive learning rate updating to enhance target tracking precision. The results of the comparison experiments with the state-of-the-art algorithms on the UAVDark135, UAVDT, and DTB70 datasets show that the algorithm in this paper outperforms the state-of-the-art tracking methods and has better tracking performance under light changes and fast motion (FM) scenarios. The tracking speed on a single Central processing unit (CPU) reaches 49 FPS, which satisfies the real-time requirement of UAV tracking. [ABSTRACT FROM AUTHOR]

This paper combines the boundary box regression with the training data occlusion processing method, the occlusion problem is more accurate and the tracking accuracy is improved. The occlusion problem is now the major challenge in target tracking. This paper puts forward a weakly monitoring framework to address this problem. The main idea is to randomly hide the most discriminating patches in the input images, forcing the network to focus on other relevant parts. Our method only needs to modify the inputs, no need to hide any patches during the test. [ABSTRACT FROM AUTHOR]

Gaining environmental awareness through lateral head scanning (yaw rotations) is important for driving safety, especially when approaching intersections. Therefore, head scanning movements could be an important behavioral metric for driving safety research and driving risk mitigation systems. Tracking head scanning movements with a single in-car camera is preferred hardware-wise, but it is very challenging to track the head over almost a 1 8 0 ∘ range. In this paper, we investigate two state-of-the-art methods, a multi-loss deep residual learning method with 50 layers (multi-loss ResNet-50) and an ORB feature-based simultaneous localization and mapping method (ORB-SLAM). While deep learning methods have been extensively studied for head pose detection, this is the first study in which SLAM has been employed to innovatively track head scanning over a very wide range. Our laboratory experimental results showed that ORB-SLAM was more accurate than multi-loss ResNet-50, which often failed when many facial features were not in the view. On the contrary, ORB-SLAM was able to continue tracking as it does not rely on particular facial features. Testing with real driving videos demonstrated the feasibility of using ORB-SLAM for tracking large lateral head scans in naturalistic video data. [ABSTRACT FROM AUTHOR]

This paper presents a coarse-fine self-learning active mass damper (AMD) for frequency tracking vibration control. Even though the AMD is under unknown disturbance, it can obtain the exact exciting frequency of primary system after several self tries and achieve significant vibration suppression. The frequency tuning algorithm consists of two improved techniques, namely, the variable-gain frequency estimator and variable learning rate Q (λ) -learning algorithm, both aim to accelerate the convergence speed of frequency estimation. The coarse tuning method helps to tune the AMD's natural frequency in a relatively wide effective bandwidth using frequency estimator and the fine tuning method can achieve precise tune in a tiny-scale bandwidth. The simulation results demonstrate that this coarse-fine learning AMD can help obtain the exact exciting frequency after several times of self-learning, and the vibration of primary system is dramatically attenuated by tuning the AMD's natural frequency to match with the exciting frequency. This is the first time for the tuning method of mass damper proposed using machine learning, which can help obtain the exact exciting frequency after several self-tries. [ABSTRACT FROM AUTHOR]

This paper proposes a simultaneous localization and mapping (SLAM)-based markerless mobile-end tracking registration algorithm to address the problem of virtual image drift caused by fast camera motion in mobile-augmented reality (AR). The proposed algorithm combines the AGAST-FREAK-SLAM algorithm with inertial measurement unit (IMU) data to construct a scene map and localize the camera's pose. The extracted feature points are matched with feature points in a map library for real-time camera localization and precise registration of virtual objects. Experimental results show that the proposed method can track feature points in real time, accurately construct scene maps, and locate cameras; moreover, it improves upon the tracking and registration robustness of earlier algorithms. [ABSTRACT FROM AUTHOR]

This paper discusses the existence of the tracking technique for a two-dimensional Brownian particle on a planar surface. The tracking process starts from the origin of the plane (intersection point of x and y axes). Accordingly, we derive the conditions that make the expected value of the first meeting time between the sensor and the particle finite. Also, we calculate the approximated expected value of the first meeting time. [ABSTRACT FROM AUTHOR]

In this paper, we propose a strong spatio-temporal mechanism with correlation filters to solve multi-modality tracking tasks. First, we use the features of the previous four frames as spatio-temporal features, then aggregate the spatio-temporal features into the filters learning and positioning of the adjacent frame. Second, we enhance the temporal and spatial characteristics of the current frame filter by learning the previous four frame filters and spatial penalty. From the experimental results on the GTOT, VOT-TIR2019 and RGBT234 datasets, our strong spatio-temporal correlation filters has achieved excellent performance. [ABSTRACT FROM AUTHOR]

Object tracking is a hot topic in computer vision. The significantly developed satellite video technology makes object tracking in satellite videos possible. In recent years, Convolutional Neural Network (CNN)-based trackers have achieved satisfying performance in the visual object tracking field. However, CNN cannot be directly applied to object tracking in satellite videos due to the following two reasons. First, the feature map size generally decreases as the network layer deepens, which is unsuitable for the small targets in satellite videos. Second, CNN-based trackers commonly need extensive data to train the network parameters, while few labeled satellite videos are available. Therefore, in this paper, we design a lightweight network for the satellite video tracking task. On one hand, the network generates a response map with the same size as the input image and reserves the spatial resolution of targets. On the other hand, the network parameters are transferred from an existing network and trained with the initial annotated frame, thus no extra data are needed. To make a fair comparison between existing trackers, we further propose a simulated benchmark based on the UAV123 dataset according to the imaging characteristics of satellite videos. Experiments are conducted to compare our method with other state-of-the-art trackers on both the simulated benchmark and real satellite videos and experimental results demonstrate the superiority of our proposed algorithm. [ABSTRACT FROM AUTHOR]

Deep learning technology has greatly improved the performance of target tracking, but most recently developed tracking algorithms are short-term tracking algorithms, which cannot meet the actual engineering needs. Based on the Siamese network structure, this paper proposes a long-term tracking framework with a persistent tracking capability. The global proposal module extends the search area globally through the construction of a feature pyramid. The local regression module is mainly responsible for the confidence evaluation of the candidate regions and for performing more accurate bounding box regression. To improve the discriminative ability of the regression network, the error samples are eliminated by synthesizing the temporal information and are then classified through a verification module in advance. Experiments on the VOT long-term tracking dataset and the UAV20L aerial dataset show that the proposed algorithm achieves state-of-the-art performance. [ABSTRACT FROM AUTHOR]

Visual object tracking works as a key component for many instrumentation and measurement applications such as UAV systems, optical tracking and measuring systems. This paper investigates how to implement accurate RGB-T tracking by integrating the complementary information from RGB and thermal sources. Inspired by the success of Siamese networks in the RGB tracking field, we design a twofold Siamese network for RGB-T tracking, which is composed of an RGB branch and a thermal branch. Each branch is a Siamese network, which can be utilized to compute similarities between the search image and the exemplar image. The parameters in the RGB branch are kept the same as SiamFC. The thermal branch is initialized with parameter weights of the trained network in SiamFC and fine-tuned with constructed thermal image pairs to better capture the target characteristics in the thermal data. Two criteria are further proposed to measure the confidence degrees of response maps obtained by these two modalities. The final response map is computed by adaptively fusing them according to their confidence degrees. The maximum location on the final response map is identified as the target location, and the target scale is obtained through a simple multi-scale search. Experiments on the recently public benchmark RGB-T234 demonstrate the effectiveness of our proposed method when compared to other state-of-the-art trackers. The high performance of our proposed trakcer makes it easy to be implemented in embedded system. [ABSTRACT FROM AUTHOR]

Motion detection and object tracking play important roles in unsupervised human–machine interaction systems. Nevertheless, the human–machine interaction would become invalid when the system fails to detect the scene objects correctly due to occlusion and limited field of view. Thus, robust long-term tracking of scene objects is vital. In this paper, we present a 3D motion detection and long-term tracking system with simultaneous 3D reconstruction of dynamic objects. In order to achieve the high precision motion detection, an optimization framework with a novel motion pose estimation energy function is provided in the proposed method by which the 3D motion pose of each object can be estimated independently. We also develop an accurate object-tracking method which combines 2D visual information and depth. We incorporate a novel boundary-optimization segmentation based on 2D visual information and depth to improve the robustness of tracking significantly. Besides, we also introduce a new fusion and updating strategy in the 3D reconstruction process. This strategy brings higher robustness to 3D motion detection. Experiments results show that, for synthetic sequences, the root-mean-square error (RMSE) of our system is much smaller than Co-Fusion (CF); our system performs extremely well in 3D motion detection accuracy. In the case of occlusion or out-of-view on real scene data, CF will suffer the loss of tracking or object-label changing, by contrast, our system can always keep the robust tracking and maintain the correct labels for each dynamic object. Therefore, our system is robust to occlusion and out-of-view application scenarios. [ABSTRACT FROM AUTHOR]

Accurate scale estimation of the target plays an important role in object tracking. Most state-of-the-art methods estimate the target size by employing an exhaustive scale search. These methods can achieve high accuracy but suffer significantly from large computational cost. In this paper, we first propose an adaptive scale search strategy with the scale selection factor instead of an exhaustive scale search. This proposed strategy contributes to reducing computational costs by adaptive sampling. Furthermore, the boundary effects of correlation filters are suppressed by investigating background information so that the accuracy of the proposed tracker can be boosted. Experiments' empirical evaluations of 61 challenging benchmark sequences demonstrate that the overall tracking performance of the proposed tracker is very successfully improved. Moreover, our method obtains the top rank in performance by outperforming 17 state-of-the-art trackers on OTB2013. [ABSTRACT FROM AUTHOR]

In this paper, we consider the nonlinear orbit tracking control of rotating multi-tethered satellite formations in Halo orbits. A dynamical formulation is first applied for a rotating multi-tethered formation arranged in a hub-spoke configuration. Then, a new nonlinear optimal tracking control method is proposed for the stabilization of the parent satellite to follow the predefined trajectory. Numerical simulations illustrating the effectiveness of the nonlinear controller are presented. The results show that the actual trajectory of the parent satellite tracks the nominal Halo orbit with good accuracy under the influence of initial injection errors and the perturbations of subsatellites. In addition, the control acceleration and the total fuel cost of the control can be quite reasonable. Furthermore, a number of the relevant parameters that affect the control costs are varied in order to demonstrate the robustness of the nonlinear controller. [ABSTRACT FROM AUTHOR]

Radio Frequency IDentification (RFID) technology has been in use for several decades to track and identify goods, assets, and even living things. Recently, however, RFID has generated widespread corporate interest as a means to waste management performance. In this paper, a vehicle routing model for waste collection is developed. The model not only uses precise data with respect to both quantity and location via RFID technology, but also includes single vehicle with a pre-determined capacity, multiple tours, and locations with deterministic waste quantities. Then a numerical example is solved via Dash Optimization XPress Solver to find an optimal route considering the locations of waste bins and the waste quantities. The impact of changing waste quantity on the operation cost is investigated considering the distance of the waste bins using variance analysis (ANOVA). With this method, municipality authorities can better manage itineraries and manpower, and have a monitoring system for the volume of the waste produced in the region of their responsibility. [ABSTRACT FROM AUTHOR]

Aiming to tackle the problem of tracking drift easily caused by complex factors during the tracking process, this paper proposes an improved object tracking method under the framework of kernel correlation filter. To achieve discriminative information that is not sensitive to object appearance change, it combines dimensionality-reduced Histogram of Oriented Gradients features and Lab color features, which can be used to exploit the complementary characteristics robustly. Based on the idea of multi-resolution pyramid theory, a multi-scale model of the object is constructed, and the optimal scale for tracking the object is found according to the confidence maps' response peaks of different sizes. For the case that tracking failure can easily occur when there exists inappropriate updating in the model, it detects occlusion based on whether the occlusion rate of the response peak corresponding to the best object state is less than a set threshold. At the same time, Kalman filter is used to record the motion feature information of the object before occlusion, and predict the state of the object disturbed by occlusion, which can achieve robust tracking of the object affected by occlusion influence. Experimental results show the effectiveness of the proposed method in handling various internal and external interferences under challenging environments. [ABSTRACT FROM AUTHOR]

Dance movement is intrinsically connected to the rhythm of music and is a fundamental form of nonverbal communication present in daily human interactions. In order to enable robots to interact with humans in natural real-world environments through dance, these robots must be able to listen to music while robustly tracking the beat of continuous musical stimuli and simultaneously responding to human speech. In this paper, we propose the integration of a real-time beat tracking system with state recovery with different preprocessing solutions used in robot audition for its application to interactive dancing robots. The proposed system is assessed under different real-world acoustic conditions of increasing complexity, which consider multiple audio sources of different kinds, multiple noise sources of different natures, continuous musical and speech stimuli, and the effects of beat-synchronous ego-motion noise and of jittering in ego noise (EN). The overall results suggest improved beat tracking accuracy with lower reaction times to music transitions, while still enhancing automatic speech recognition (ASR) run in parallel in the most challenging conditions. These results corroborate the application of the proposed system for interactive dancing robots. [ABSTRACT FROM AUTHOR]

In recent years, with the growth of China's economy and the development of the automobile manufacturing industry, the number of various vehicles has continuously increased, and the incidence of traffic accidents has also increased. Especially in traffic blind areas, right-turning areas of vehicles, etc., traffic accidents such as vehicle collisions are extremely easy to occur, which poses a serious threat to people's lives and property, and is extremely harmful. Therefore, related research on collision detection of people and vehicles has been traffic-safe and has received extensive attention from field researchers. At present, the research on human-vehicle collision detection is to detect human-vehicle collision accidents by tracking the track of vehicles and pedestrians, but there are problems such as poor tracking effect, low accuracy of collision discrimination and complex algorithms. Aiming at these problems, this paper studies the human-vehicle collision detection algorithm based on image processing. Through the image processing of traffic monitoring video, the vehicle and pedestrian contour information is extracted. Based on this, a mathematical model for collision detection is constructed to realize human-vehicle collision detection. The results show that the proposed method can effectively distinguish the collision between pedestrians and vehicles, and the algorithm for image processing is simpler than the traditional tracking algorithm, and the time is shorter. The results show that the image-based collision detection algorithm based on image processing can effectively and quickly identify the traffic accidents in which people and vehicles collide, and then can issue alarm signals in time, shortening the accident processing time and reducing the accident time. The possibility of a secondary accident has a high practicability in the detection of traffic accidents in which people and vehicles collide. [ABSTRACT FROM AUTHOR]

Collecting data like location information is an essential part of concepts like the "IoT" or "Industry 4.0". In the case of the development of a precise localization system and an integrated navigation system, indoor location technology receives more and more attention and has become a hot research topic. Common indoor location techniques are mainly based on wireless local area network, radio frequency tag, ZigBee technology, Bluetooth technology, infrared technology and ultra-wideband (UWB). However, these techniques are vulnerable to various noise signals and indoor environments, and also the positioning accuracy is easily affected by the complicated indoor environment. We studied the problem of real-time location tracking based on UWB in an indoor environment in this paper. We have proposed a combinational filtering algorithm and an improved Two-Way Ranging (ITWR) method for indoor real-time location tracking. The simulation results prove that the real-time performance and high accuracy of the presented algorithm can improve location accuracy. The experiment shows that the combinational algorithm and ITWR method which are applied to the positioning and navigation of the smart supermarket, have achieved quiet good results in positioning accuracy. The average positioning error is less than 10 cm, some of the improvements can elevate the positioning accuracy by 17.5%. UWB is a suitable method for indoor real-time location tracking and has important theoretic value and practical significance. [ABSTRACT FROM AUTHOR]

In the field of printed electronics, there are many kinds of ink with a variety of performance and parameters. In order to generate high-quality droplets, it is necessary to eject droplet for testing in order to discover the appropriate excitation voltage and waveform shape. Consequently, a real-time and efficient droplet monitoring system is needed to monitor droplet formation quality. A multi-satellite droplet monitoring system is proposed in this paper. It can not only monitor the droplet with multiple satellites but also can generate the instantaneous droplet position curve, length curve and velocity curve. The waveform voltage and dwell time can be adjusted in real-time to obtain droplets with higher quality and efficiency. [ABSTRACT FROM AUTHOR]

This paper addresses the pilot-aided multiuser least square (LS) channel estimation for the uplink of multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The systems under consideration allow all users use all available subcarriers independently and thus involve multiuser interference in the frequency domain. Direct application of the known pilot-aided single-user channel estimation methods to these systems is prohibited, requiring much more new investigations. The decentralized and centralized channel estimation algorithms are developed according to different multiuser scenarios. Optimal multiuser pilots are proposed, especially for centralized estimation methods with respect to the mean square error (MSE) of LS channel estimate. In addition, channel tracking algorithms are represented in terms of individual user's channels. [ABSTRACT FROM AUTHOR]

In this paper, we address the problem of detection and analysis of moving objects in a video stream obtained by a fixed camera. To detect the moving objects, the tradition method is to create a fixed image first, which includes all the motionless parts of the scene, known as the background model. The difficulty of this approach lies mainly in two aspects: The first relates to the fact that a slow moving object can leave a visible trace in background model. The latter comes from the variation of illumination in the course of time so it cannot obtain a reasonable background model. To overcome these difficulties, we propose a multiple background model. At the exit of the detection of moving objects, the tracking (matching) of a moving object extracted in the successive images is necessary to analyze its behavior. After the matching of mobile objects, a series of analysis methods are presented. The proposed tracking and analysis methods allow dealing with partial occlusions, stopping and going motion, moving directions, crossing of moving object in very challenging situations. The experiment and comparison results are reported for different real sequences, which show better performance of our methods. [ABSTRACT FROM AUTHOR]

In this paper the path tracking problem for non-holonomic mobile robots is dealt with. The model used is known as the Dubins Car model. A robust fuzzy logic controller that steers the car to the appropriate direction is proposed. A technique called "spatial window technique" which greatly increases the overall performance of the control scheme is also introduced. The simulations of this scheme show that the path following problem is treated very adequately and the noise tolerance of the overall system is high. [ABSTRACT FROM AUTHOR]

In view of the multipeak characteristics of a photovoltaic (PV) array P–V curve under local shadow conditions and that the traditional maximum power point tracking (MPPT) algorithm cannot effectively track the maximum power point of the curve, a multipeak MPPT algorithm based on a chaotic quantum bee colony and support vector regression (SVR) is proposed. By constructing and analyzing the mathematical model of a photovoltaic array under a local shadow, the P–V characteristic equation of the photovoltaic array is obtained. The improved strategy of the artificial bee colony algorithm is studied, and the improved chaotic quantum bee colony algorithm (CQABC) is applied to the optimization of SVR parameters; this application improves the accuracy and generalization performance of the maximum power point prediction model based on SVR. The calculation process of the multipeak MPPT algorithm based on CQABC-SVR is given, and the effectiveness of the algorithm is verified by simulation and testing. The experimental results show that the algorithm can accurately track the global maximum power point under uniform illumination or local shadow conditions, effectively overcoming the problem of traditional MPPT algorithms easily falling into local extrema. [ABSTRACT FROM AUTHOR]

The new technique of measuring frequency by optical lattice clocks now approaches to the relative precision of (Δ f / f) = O (1 0 − 1 8). We propose to place such precise clocks in space and to use Doppler tracking method for detecting low-frequency gravitational wave below 1 Hz. Our idea is to locate three spacecrafts at one A.U. distance (say at L1, L4 and L5 of the Sun–Earth orbit), and apply the Doppler tracking method by communicating "the time" each other. Applying the current available technologies, we obtain the sensitivity for gravitational wave with third- or fourth-order improvement ( h n ∼ 1 0 − 1 7 or 1 0 − 1 8 level in 1 0 − 5 – 1 Hz) than that of Cassini spacecraft in 2001. This sensitivity enables us to observe black hole (BH) mergers of their mass greater than 1 0 5 M ⊙ in the cosmological scale. Based on the hierarchical growth model of BHs in galaxies, we estimate the event rate of detection will be 20–50 a year. We nickname "INO" (Interplanetary Network of Optical Lattice Clocks) for this system, named after Tadataka Ino (1745–1818), a Japanese astronomer, cartographer, and geodesist. [ABSTRACT FROM AUTHOR]

Widespread availability of location aware devices (such as GPS receivers) promotes capture of detailed movement trajectories of people, animals, vehicles and other moving objects. We investigate spatio-temporal movement patterns in large tracking data sets, i.e. in large sets of polygonal paths. Specifically, we study so-called 'popular places', that is, regions that are visited by many entities. Given a set of polygonal paths with a total of $\bar n$ vertices, we look at the problem of computing such popular places in two different settings. For the discrete model, where only the vertices of the polygonal paths are considered, we propose an $O(\bar n \log \bar n)$ algorithm; and for the continuous model, where also the straight line segments between the vertices of a polygonal path are considered, we develop an $O(\bar n^2)$ algorithm. We also present lower bounds and hardness results. [ABSTRACT FROM AUTHOR]