Ship motion is an important influencing factor in passenger ship evacuation that affects the entire evacuation process by reducing individual walking speed. This study used Dalian Maritime University's training ship to conduct human walking experiments to study the influence of ship motion onNormal and fast walking speeds.It was found that during the berthing period, the individual Normal walking speed was 1.28-1.68 m/s, and the fast walking speed was 1.50-2.14 m/s. During the voyage, the ship's rolling motion reduced the Normal walking speed by 3.8%-10.3% and the fast walking speed by 3.7-14.0%. Due to the influence of ship rolling, the higher the deck and the farther away the rolling centre is, the smaller the athwartship and fore-aft walking speeds. Athwartship walking was slightly faster than fore-aft walking. In the Normal walking mode, the athwartship walking speed was 1.6%-3.7% faster than fore-aft walking, and in the fast walking mode, the athwartship walking speed was 0.8%-4.9% faster than fore-aft walking. During the berthing period, the average speed of the younger group was 24.1% higher than that of the older group. During the voyage, the reduction ratio of the individual walking speed was 86.0%-96.2%, and the value decreased as the deck height increased.
Facilitated by recent establishment of terrestrial networks and satellite constellations of Automatic Identification System (AIS) receivers, ship trajectories are becoming increasingly available and the size of recorded trajectories is getting larger. Large sets of trajectories create problems of storing, transmitting and processing data. Using appropriate methods, an accurate representation of the original trajectories can be obtained by compressing redundant information, while maintaining the main characteristic elements. In this paper, a new scheme and the implementation of the Douglas-Peucker (DP) algorithm are presented, which can simplify AIS trajectories by extracting characteristic points. As for the simplification threshold, the solo parameter of the DP algorithm, a new AIS-based minimum ship domain evaluation method is proposed and acts as criteria for simplification threshold determination. Finally, a validation is made to examine the effectiveness of the DP simplification algorithm and the rationality of the simplification threshold. The result indicates that the DP algorithm can simplify AIS trajectories effectively; the simplification threshold is scientific and reasonable.
Autonomous ships are gaining in importance and are expected to shape the future of the global shipping industry. This evolutionary shift raises serious issues about compliance with the International Regulations for Preventing Collisions at Sea 1972 (COLREGs). This paper reviews the literature on autonomous ships from the perspective of the obligations of good seamanship imposed by COLREGs. The authors conclude that to facilitate the introduction of autonomous ships, the application barriers presented by COLREGs need to be analysed. With this goal, this paper presents a perspective from navigational practice. Four nautical scientists and two deck officers were invited to give their opinions. The analysis indicates that COLREGs require further elaboration and amendments to eliminate uncertainty of interpretation. In particular, the paper highlights the need to amend the ‘look-out’ rule (COLREGs Rule 5) to permit look-out by ‘computer vision’ alone while, at the same time, preserving the distinction between vessels navigating in restricted visibility and in sight of one another.
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