Modeling Marine Traffic Density and Flow as S-100 Grid Hydrographic Data

Marine traffic information supports the safe and efficient operation of ships and has been produced in various ways from Automatic Identification System (AIS) data. However, existing outputs differ in grid size, aggregation method, and format and cannot be used with charts on navigation equipment. This study defines historical marine traffic information, namely traffic density and flow, as gridded hydrographic data based on the International Hydrographic Organization (IHO) S-100 Universal Hydrographic Data Model. Based on a previously proposed high-resolution traffic flow model, an application schema, a Feature Catalogue, and a Portrayal Catalogue were designed, and the data were encoded in HDF5. Density is portrayed by color levels, and flow by arrow symbols that combine speed, density, and direction. A dataset was built from two years of AIS data for the coastal waters of Mokpo, Republic of Korea, and its values and portrayal rules were verified quantitatively. The density was displayed in a third-party S-100 viewer using only the catalogues and dataset, whereas the flow was displayed only in a simulator based on an in-house S-100 chart engine. These results show that historical marine traffic information can be defined, encoded, and portrayed as S-100 gridded data; operational interoperability remains to be verified.