Mental Map Preservation in Annotating Metro Maps

Metro maps serve as the common media for travelers to explore the transportation networks of the metro lines available in major cities. Such maps are often transformed into schematic diagrams for better readability of the network topology. Recent advancement of practical techniques enables to automatically schematize geographical layouts of metro networks in a visually plausible fashion. Properly labeling station names on the schematic metro maps is also important, while this usually incurs additional technical challenges. This is primarily because the central downtown area of such a schematic map is usually congested with multiple metro lines around the interchange stations and thus we cannot find enough space for labeling station names, when compared with sparse rural areas around the terminals of the metro lines. The problem is often alleviated by manually sparing more labeling space around the stations in the congested downtown areas, which usually incurs a lengthy trial and error process. It is also infeasible to optimize the layout of the metro network and placement of station names simultaneously because we have to enumerate an excessive number of possible solutions for this combinatorial problem in this case.

In this project, we developed a progressive approach for automatically annotating stations with their names while maximally respecting the original layout of the schematic metro map. For this purpose, we properly preserve the underlying mental map of the original schematic metro map by imposing additional constraints to restrict the variation in the aspect ratios of the regions confined by the metro network. The feasibility of the proposed approach has been demonstrated by presenting experimental results together with the evaluation through a user study.