DiffTraj: Generating GPS Trajectory with Diffusion Probabilistic Model
This work addresses privacy concerns in GPS data for spatial-temporal data mining, offering a novel method for trajectory generation, though it is incremental as it adapts diffusion models to a specific domain.
The authors tackled the problem of generating privacy-preserving GPS trajectories by proposing DiffTraj, a spatial-temporal diffusion probabilistic model that synthesizes high-fidelity trajectories from noise, with experiments on real-world datasets showing it outperforms other methods in geo-distribution evaluations.
Pervasive integration of GPS-enabled devices and data acquisition technologies has led to an exponential increase in GPS trajectory data, fostering advancements in spatial-temporal data mining research. Nonetheless, GPS trajectories contain personal geolocation information, rendering serious privacy concerns when working with raw data. A promising approach to address this issue is trajectory generation, which involves replacing original data with generated, privacy-free alternatives. Despite the potential of trajectory generation, the complex nature of human behavior and its inherent stochastic characteristics pose challenges in generating high-quality trajectories. In this work, we propose a spatial-temporal diffusion probabilistic model for trajectory generation (DiffTraj). This model effectively combines the generative abilities of diffusion models with the spatial-temporal features derived from real trajectories. The core idea is to reconstruct and synthesize geographic trajectories from white noise through a reverse trajectory denoising process. Furthermore, we propose a Trajectory UNet (Traj-UNet) deep neural network to embed conditional information and accurately estimate noise levels during the reverse process. Experiments on two real-world datasets show that DiffTraj can be intuitively applied to generate high-fidelity trajectories while retaining the original distributions. Moreover, the generated results can support downstream trajectory analysis tasks and significantly outperform other methods in terms of geo-distribution evaluations.