Uncertainty-Aware BIT*: Collision-Free Path Planning for Maritime Autonomous Surface Ships under Target Ship Position Uncertainty

Abstract

This paper proposes a BIT*-based collision-free path planning method for remotely operated Maritime Autonomous Surface Ships (MASS) under target ship position uncertainty. In a remote operating environment, the Remote Operating Center (ROC) receives target ship position data from long-range sensors such as AIS and radar. This data inherently contains uncertainty due to measurement errors and communication delays, making it essential to account for such uncertainty during path planning. As MASS must comply with the International Regulations for Preventing Collisions at Sea (COLREGs) during navigation, path planning must also reflect these requirements. The proposed method models target ship position uncertainty as a two-dimensional Gaussian distribution and incorporates it into edge evaluation as a collision risk cost, while applying penalty costs to edges that enter COLREGs non-compliant regions. A turning radius constraint is also incorporated into the edge selection process to ensure navigational feasibility. The method is validated through headon and crossing encounter simulations on an Electronic Nautical Chart (ENC)-based grid map of Ulsan Port, South Korea. The results show that higher levels of position uncertainty lead to more conservative avoidance paths, resulting in greater Distance to Closest Point of Approach (DCPA).