AIS Data as Trajectories and Heat Maps

All large ships are by international law required to provide their position, speed, and course while sailing. This data is called AIS data. Several maritime organizations make this data freely available. In this paper, we present two approaches to querying AIS data. The first approach combines the individual AIS data records into trajectories and the second approach is to combine many trajectories into heat maps. The first approach is well suited, e.g., to find the complete route of a few ships or study how many ships are navigating in a smaller area known to be complicated to sail. The heat-map approach is particularly well suited to provide an overview of ship movements in large areas. For the trajectory approach, we introduce and define a novel way to query AIS data called a trident query. This query type is developed in close collaboration with domain experts. The core idea with a trident query is to visualize route choices. The heat-map approach works both for user-defined areas and for predefined Areas Of Interest (AOI) cells. The trajectory approach is difficult to scale and we show how the trajectories can be simplified to make querying and visualization more efficient. We present data on a map and statistical details are provided in graphs and tables, e.g., the distribution of ship types and ship dimensions (length, width, and draught). End-users can filter on attributes such as ship IDs, ship types, and ship dimensions for both the trajectory and heap-map approaches.