Spatio-Temporal Top-k Similarity Search for Trajectories in Graphs

TL;DR

This paper introduces an efficient indexing method for top-k spatio-temporal trajectory similarity search in graphs, improving query speed and memory usage while maintaining high accuracy.

Contribution

It proposes a new spatio-temporal distance function satisfying a triangle inequality and develops index structures that enable fast, memory-efficient top-k trajectory searches.

Findings

Significantly faster indexing times compared to baselines

Comparable or improved query response times

High-quality results in real-world and synthetic datasets

Abstract

We study the problem of finding the $k$ most similar trajectories to a given query trajectory. Our work is inspired by the work of Grossi et al. [6] that considers trajectories as walks in a graph. Each visited vertex is accompanied by a time-interval. Grossi et al. define a similarity function that captures temporal and spatial aspects. We improve this similarity function to derive a new spatio-temporal distance function for which we can show that a specific type of triangle inequality is satisfied. This distance function is the basis for our index structures, which can be constructed efficiently, need only linear memory, and can quickly answer queries for the top-$k$ most similar trajectories. Our evaluation on real-world and synthetic data sets shows that our algorithms outperform the baselines with respect to indexing time by several orders of magnitude while achieving similar or better query time and quality of results.