Trajectory Prediction from Hierarchical Perspective

Predicting the future trajectories of multiple agents is essential for various applications in real life, such as surveillance systems, autonomous driving and social robots. The trajectory prediction task is influenced by many factors, including the individual historical trajectory, interactions between agents and fuzzy nature of an agent's motion. While existing methods have made great progress on the topic of trajectory prediction, they treat all the information uniformly, which limits the sufficiency of using information. To this end, in this paper, we propose to regard all the information in a two-level hierarchical view. Particularly, the first-level view is the inter-trajectory view. In this level, we observe that the difficulty to predict different trajectory samples is different. We define trajectory difficulty and train the proposed model in an "easy-to-hard'' schema. The second-level view is the intra-trajectory level. We find the influencing factors for a particular trajectory can be divided into two parts. The first part is global features, which keep stable within a trajectory, i.e., the expected destination. The second part is local features, which change over time, i.e., the current position. We believe that the two types of information should be handled in different ways. The hierarchical view is beneficial to take full advantage of the information in a fine-grained way. Experimental results validate the effectiveness of the proposed model.