Decluttering of Icons Based on Aggregation in Mobile Maps

In this chapter, we will deal with cluttering issues associated with the visualization of a high number of icons, representing Points of Interest, on mobile maps. Clutter is a frequently occuring problem that makes it difficult to understand the visualization and has the even more critical effect of masking data. As the user zooms out, the positions of icons increasingly converge until they partially or entirely overlap each other. In regions of high icon density, this effect impairs even the effectiveness of a close-up view. Finding ways to visualize icons in a comprehensible uncluttered fashion is a challenging task. We will first discuss techniques which have been previously proposed in the literature for the automatic placement of labels on maps, a problem which is closely related to the placement of icons. We will then propose an approach for icons aggregation aimed at mitigating cluttering issues when icon density is high. The approach is based on an aggregation algorithm to reduce the total number of icons that need to be displayed and on the design of icons that could function as both individuals and aggregates.