A Principled Distributional Approach to Trajectory Similarity Measurement and its Application to Anomaly Detection

This paper aims to solve two enduring challenges in existing trajectory similarity measures: computational inefficiency and the absence of the 'uniqueness' property that should be guaranteed in a distance function: dist(X, Y ) = 0 if and only if X = Y, where X and Y are two trajectories. In this work, we present a novel approach utilizing a distributional kernel for trajectory representation and similarity measurement, based on the kernel mean embedding framework. It is the very first time a distributional kernel is used for trajectory representation and similarity measurement. Our method does not rely on point-to-point distances which are used in most existing distances for trajectories. Unlike prevalent learning and deep learning approaches, our method requires no learning. We show the generality of this new approach in anomalous trajectory and sub-trajectory detection. We identify that the distributional kernel has (i) a data-dependent property and the 'uniqueness' property which are the key factors that lead to its superior task-specific performance, and (ii) runtime orders of magnitude faster than existing distance measures.