Unraveling "waves" in liner shipping. A 2D method for visualizing individual vessel trajectories with AIS data

Liner shipping is often marked by operational regularities, with vessels operating on designated services calling at specific ports at specific times. Deviations from these patterns can be small and confined in space and in time, but they can also be much more consequential, like recent disruptions tied to the COVID-19 pandemic, the Red Sea crisis or the Panama Canal bottleneck. This underscores the necessity of understanding individual vessel trajectory configurations, monitoring vessel trajectories and identifying deviations from usual patterns prior to conducting aggregated analyses of vessel movements. This paper examines various visualization methods, including traditional 2D mapping and 3D space-time cubes, and concludes that the latter are often inadequate for visualizing vessel loops and deviations over extended time periods with enough detail to inform about vessel operations, shipping operators' strategies, and the scope of disruptions to supply chains. To overcome the limitations of existing methods, this paper introduces a novel approach based on linear referencing. Instead of relying on geographic coordinates, ports are sequenced by relative positions along a line feature that follows the coasts of various world regions consecutively. The resulting wave-like patterns, which represent time on one axis and a linear referencing of ports on the other, enable rapid identification of regular "waves" and of deviations in vessel trajectories and their magnitude within their geographic and temporal context. The new visualization method complements existing ones, as illustrated by select cases of vessels discussed in the paper.