A Focus Control Method Based on City Blocks for the Focus+Glue+Context Map

In order to show both a detailed map (Focus) and a wide-area map (Context) in one map, we have proposed the Focus+Glue+Context map, a type of fisheye view for mobile maps. A problem in the Focus+Glue+Context map is that if the radius of the Focus is large, the Context area is very narrow, and if the radius of the Focus is small, we cannot show the entire target area. To solve this problem, we have to determine the radius of the Focus according to the shape of the target area. In this work, we have proposed the Expand Loop Road algorithm to controls the radius and position of the Focus by city block. Moreover, we applied this method to a Focus+Glue+Context map service. Although the conventional method, which controls the radius of the Focus by a constant scale, has to operate 7.0 times to achieve 80% accuracy, the proposed method operates only 1.07 times to achieve 82.6% accuracy. In the future, the proposed method will enable mobile maps with fisheye views to be controlled easily based on road networks.