Focus+context metro map layout and annotation

Annotated metro maps, which are a graphic representation abstracting a city's transportation network and providing additional details about a city, can be difficult to draw because of the landmark density around many city centers. A focus+context illustrated map is therefore commonly used to provide detailed information around a focus region while preserving the context area, so that map readers can retain a mental image of a city. Nonetheless, conventional techniques do not sufficiently retain layout octilinearity of the navigation system, especially when large deformations are required, as when there are significant landmarks around central stations. This paper introduces focus+context annotated metro maps, a design emphasizing focus regions by embedding landmark icons around the stations together with aesthetically aligning metro lines and label leaders in an octilinear fashion. Our idea is to employ the conventional fisheye technique when considering appropriate edge lengths in a focus region and to generate sufficient space around the labeled stations by introducing a relative neighborhood graph for deformation purposes. This is accomplished by introducing appropriate design conditions into a linear program so that we can constrain the positions of stations and labels while preserving octilinearty within both the focus and context regions. The optimization problem is then solved in a least square sense. We also provide a user interface for customizing maps through intervention and present several design examples to demonstrate the effectiveness of the approach.