Making a semi-convex Focus area in a Focus+Glue+Context map, considering map visibility and transport access points

Abstract

We previously implemented the Focus+Glue+Context map system EMMA that provides local detailed data in Focus, global context data in Context, and connection data between both in the same view. Introducing the Glue area between Focus and Context makes it possible to provide uniform scaling for the two latter areas. This paper enhances EMMA through the implementation of a Focus creation function that considers transportation access points, such as stations and bus stops. The enhanced EMMA searches a route from the current location to the transportation access point, and allows users to identify the spatial relationship between the various locations in a small-scale Context, and view the route from the current location to the transportation access points in a large-scale Focus. However, if Focus is too large because of unnecessary areas used to identify the route, some parts of Context might be hidden by Focus. The proposed system solves this problem by implementing the following functions: (1) it searches stations that are adjacent to the current location and makes a semiconvex Focus that includes the current location and those stations in order for Focus to include really necessary areas. (2) It reduces Focus distortion by setting a fixed point as the center of the Focus area. (3) It smoothens the Focus shape in order to improve visibility in the Glue area. We developed a prototype of the proposed system that implements these functions.