Deviation Point Curriculum Learning for Trajectory Outlier Detection in Cooperative Intelligent Transport Systems

Cooperative Intelligent Transport Systems (C-ITS) are emerging in the field of transportation systems, which can be used to provide safety, sustainability, efficiency, communication and cooperation between vehicles, roadside units, and traffic command centres. With improved network structure and traffic mobility, a large amount of trajectory-based data is generated. Trajectory-based knowledge graphs help to give semantic and interconnection capabilities for intelligent transport systems. Prior works consider trajectory as the single point of deviation for the individual outliers. However, in real-world transportation systems, trajectory outliers can be seen in the groups, e.g., a group of vehicles that deviates from a single point based on the maintenance of streets in the vicinity of the intelligent transportation system. In this paper, we propose a trajectory deviation point embedding and deep clustering method for outlier detection. We first initiate network structure and nodes' neighbours to construct a structural embedding by preserving nodes relationships. We then implement a method to learn the latent representation of deviation points in road network structures. A hierarchy multilayer graph is designed with a biased random walk to generate a set of sequences. This sequence is implemented to tune the node embeddings. After that, embedding values of the node were averaged to get the trip embedding. Finally, LSTM-based pairwise classification method is initiated to cluster the embedding with similarity-based measures. The results obtained from the experiments indicate that the proposed learning trajectory embedding captured structural identity and increased F-measure by 5.06% and 2.4% while compared with generic Node2Vec and Struct2Vec methods.acceptedVersio

Trajectory outlier detection: Algorithms, taxonomies, evaluation, and open challenges

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Scalable Techniques for Trajectory Outlier Detection

University of Minnesota M.S. thesis. June 2019. Major: Computer Science. Advisor: Eleazar Leal. 1 computer file (PDF); viii, 52 pages.The recent improvements in tracking devices and positioning satellites have led to an increased availability of spatial data describing the movement of objects such as vehicles, animals, etc. Such data is obtained by recording the positions of the objects at regular intervals and then arranging the collected positions of each object into a time-ordered sequence called trajectory. The high availability of trajectory data has permitted the execution of data analysis operations such as trajectory outlier detection, which consists in the identification of those trajectories that behave much differently from the rest of the trajectories in a database. There are several time-critical applications such as traffic management systems, security surveillance systems and real-time stock monitoring, etc. which can be solved through trajectory outlier detection. However, the time-critical nature of such applications imposes tight constraints on the execution time of trajectory outlier detection algorithms. To deal with these constraints, we propose three strategies to accelerate the performance of the existing trajectory outlier detection algorithm ODMTS. First, we consider using spatial data structures such as k-d trees and R-trees to improve the running time performance of the ODMTS algorithm for trajectory outlier detection. Our results showed that by using R-trees we can improve the execution time of ODMTS by a factor of 10X. Our second strategy consists in harnessing the power of multiple CPUs to parallelize the ODMTS algorithm. This strategy yielded an execution time improvement that scales linearly with the number of cores, which in our case achieved 32X. The third strategy consists in a new partitioning-based streaming algorithm, called PDMTS, for trajectory outlier detection that leverages data streams in order to find trajectory outliers. Our experiments on real-life datasets showed that our proposed algorithm detected almost 45% outliers more than ODMTS, but is almost 18% slower than compared to ODMTS due to the partitioning step

Unsupervised Action Proposal Ranking through Proposal Recombination

Recently, action proposal methods have played an important role in action recognition tasks, as they reduce the search space dramatically. Most unsupervised action proposal methods tend to generate hundreds of action proposals which include many noisy, inconsistent, and unranked action proposals, while supervised action proposal methods take advantage of predefined object detectors (e.g., human detector) to refine and score the action proposals, but they require thousands of manual annotations to train. Given the action proposals in a video, the goal of the proposed work is to generate a few better action proposals that are ranked properly. In our approach, we first divide action proposal into sub-proposal and then use Dynamic Programming based graph optimization scheme to select the optimal combinations of sub-proposals from different proposals and assign each new proposal a score. We propose a new unsupervised image-based actioness detector that leverages web images and employs it as one of the node scores in our graph formulation. Moreover, we capture motion information by estimating the number of motion contours within each action proposal patch. The proposed method is an unsupervised method that neither needs bounding box annotations nor video level labels, which is desirable with the current explosion of large-scale action datasets. Our approach is generic and does not depend on a specific action proposal method. We evaluate our approach on several publicly available trimmed and un-trimmed datasets and obtain better performance compared to several proposal ranking methods. In addition, we demonstrate that properly ranked proposals produce significantly better action detection as compared to state-of-the-art proposal based methods

Real-time detection of moving crowds using spatio-temporal data streams

Over the last decade we have seen a tremendous change in Location Based Services. From primitive reactive applications, explicitly invoked by users, they have evolved into modern complex proactive systems, that are able to automatically provide information based on context and user location. This was caused by the rapid development of outdoor and indoor positioning technologies. GPS modules, which are now included almost into every device, together with indoor technologies, based on WiFi fingerprinting or Bluetooth beacons, allow to determine the user location almost everywhere and at any time. This also led to an enormous growth of spatio-temporal data. Being very efficient using user-centric approach for a single target current Location Based Services remain quite primitive in the area of a multitarget knowledge extraction. This is rather surprising, taking into consideration the data availability and current processing technologies. Discovering useful information from the location of multiple objects is from one side limited by legal issues related to privacy and data ownership. From the other side, mining group location data over time is not a trivial task and require special algorithms and technologies in order to be effective. Recent development in data processing area has led to a huge shift from batch processing offline engines, like MapReduce, to real-time distributed streaming frameworks, like Apache Flink or Apache Spark, which are able to process huge amounts of data, including spatio-temporal datastreams. This thesis presents a system for detecting and analyzing crowds in a continuous spatio-temporal data stream. The aim of the system is to provide relevant knowledge in terms of proactive LBS. The motivation comes from the fact of constant spatio-temporal data growth and recent rapid technological development to process such data

A Survey on Urban Traffic Anomalies Detection Algorithms

© 2019 IEEE. This paper reviews the use of outlier detection approaches in urban traffic analysis. We divide existing solutions into two main categories: flow outlier detection and trajectory outlier detection. The first category groups solutions that detect flow outliers and includes statistical, similarity and pattern mining approaches. The second category contains solutions where the trajectory outliers are derived, including off-line processing for trajectory outliers and online processing for sub-trajectory outliers. Solutions in each of these categories are described, illustrated, and discussed, and open perspectives and research trends are drawn. Compared to the state-of-the-art survey papers, the contribution of this paper lies in providing a deep analysis of all the kinds of representations in urban traffic data, including flow values, segment flow values, trajectories, and sub-trajectories. In this context, we can better understand the intuition, limitations, and benefits of the existing outlier urban traffic detection algorithms. As a result, practitioners can receive some guidance for selecting the most suitable methods for their particular case

Trajectory outlier detection: New problems and solutions for smart cities

This article introduces two new problems related to trajectory outlier detection: (1) group trajectory outlier (GTO) detection and (2) deviation point detection for both individual and group of trajectory outliers. Five algorithms are proposed for the first problem by adapting DBSCAN, k nearest neighbors (kNN), and feature selection (FS). DBSCAN-GTO first applies DBSCAN to derive the micro clusters, which are considered as potential candidates. A pruning strategy based on density computation measure is then suggested to find the group of trajectory outliers. kNN-GTO recursively derives the trajectory candidates from the individual trajectory outliers and prunes them based on their density. The overall process is repeated for all individual trajectory outliers. FS-GTO considers the set of individual trajectory outliers as the set of all features, while the FS process is used to retrieve the group of trajectory outliers. The proposed algorithms are improved by incorporating ensemble learning and high-performance computing during the detection process. Moreover, we propose a general two-phase-based algorithm for detecting the deviation points, as well as a version for graphic processing units implementation using sliding windows. Experiments on a real trajectory dataset have been carried out to demonstrate the performance of the proposed approaches. The results show that they can efficiently identify useful patterns represented by group of trajectory outliers, deviation points, and that they outperform the baseline group detection algorithms