Focus+context map labeling with optimized clutter reduction
Benjamin Niedermann, Jan‐Henrik Haunert · International Journal of Cartography · 2019
Zooming is a basic operation that many digital maps support for exploring them interactively. Especially for maps on small screen devices, this is a helpful operation to uncover the user's region of interest possibly hidden by labels, e.g. points of interest represented by icons. However, by scaling the map larger the user loses the context. As a consequent the user might need to repeatedly zoom in and out to explore the map step by step.We present an approach that reduces the necessity of zooming by providing the user with the possibility of displacing the labels of a circular focus region. To that end, we utilize techniques from focus+context maps implementing the displacement of the labels by fish-eye projections. The visual association between labels and their point features is established by connecting lines aggregated to bundles. Our approach particularly guarantees that labels move smoothly when the user continuously shifts the focus region, which reduces distracting flickering effects while exploring the map by panning the map view. Further, when the user stops moving the focus region, mathematical programming is applied to optimize positions of the displaced labels. In an evaluation on real-world data and synthetically generated data, we show that our approach substantially increases the legibility of both the focus region and the displaced labels.