Anonymizing trajectory data for passenger flow analysis

• Preserve spatio-temporal data privacy and quality for passenger flow analysis.
• Make use of both global and local suppressions to achieve the requirements.
• Extensive experimental results on both real-life and synthetic trajectory data.

The increasing use of location-aware devices provides many opportunities for analyzing and mining human mobility. The trajectory of a person can be represented as a sequence of visited locations with different timestamps. Storing, sharing, and analyzing personal trajectories may pose new privacy threats. Previous studies have shown that employing traditional privacy models and anonymization methods often leads to low information quality in the resulting data. In this paper we propose a method for achieving anonymity in a trajectory database while preserving the information to support effective passenger flow analysis. Specifically, we first extract the passenger flowgraph, which is a commonly employed representation for modeling uncertain moving objects, from the raw trajectory data. We then anonymize the data with the goal of minimizing the impact on the flowgraph. Extensive experimental results on both synthetic and real-life data sets suggest that the framework is effective to overcome the special challenges in trajectory data anonymization, namely, high dimensionality, sparseness, and sequentiality.