Automatic generation of puzzle tile maps for spatial-temporal data visualization

Abstract Tile maps are a visualization tool to display geographic data without the accurate representation of geographic boundaries. Each region in a tile map is represented as a tile of identical shape and size. The tiles are fit in a regular grid at positions that approximate their geographic positions such that large regions do not dominate the map visualization, and information in small regions can be enhanced. In this study, the automatic generation of a tile map composed of puzzle tiles is proposed for spatial-temporal data visualization. A puzzle tile is an extension of a standard square tile. A sequence of connected and directional pieces in a puzzle tile is used to represent time-varying quantities in a geographic region. To generate a puzzle tile map, the proposed method includes algorithms for optimizing district-to-tile mapping according to not only geographic positions but also region orientations and for placing puzzle pieces in a tile. The proposed puzzle tile map can serve as a choropleth map in which the ordered pieces in a tile are shaded in proportion to the measurements of a statistical time variable, such as a time sequence of fertility rates, air pollution (PM2.5), or transfer of residential property, being displayed on a 2D map. Experimental demonstrations of various cases show that the proposed methods for district-to-tile mapping optimization and puzzle generation are feasible for automatic puzzle tile map generation. User studies show the capabilities of the puzzle tile map in terms of usability, readability, and comparability of spatial-temporal data visualization.