Progressive Annotation of Schematic Railway Maps

Octilinear network layouts are commonly used as the schematic representation of railway maps due to their enhanced readability. However, it is often time-consuming to place station names on such railway maps by trial and error, especially within the limited labeling space around interchange stations. This paper presents a progressive approach to placing station names around stations in schematic railway maps for better automation of map labeling processes. The idea behind our approach is to annotate stations in dense downtown areas around the interchange stations first and then those in sparse rural areas. This is achieved by introducing the sum of geodesic distances over the railway network to identify the proper order in which to annotate stations. In the actual annotation process, we increase the labeling space around the railway network when necessary by progressively stretching railway line segments while retaining their original directions, which allows us to respect the original schematic layout as much as possible. We present several experimental results to demonstrate the effectiveness of the proposed approach, together with a discussion on parameter tuning in our formulation.