Data Density Maps

Abstract

The use of the popular scatterplot method (Cleveland, 1993) is not sufficient to display all information because a great deal of overlapping occurs. When transforming data to graphical marks, a regular visualization system draws each graphical mark independently from the others: if a mark to be drawn happens to be at the same position as previously drawn marks, the system replaces (or merges using color blending) the pixels in the resulting image. The standard visualization of this pixel accumulation process is not sufficient to accurately assess their density. For instance, Figure 3.1 (left) shows one day of recorded aircraft trajectories over France with the standard color blending method. Figure 3.1 (right) shows the same dataset with a 3D and shaded density map and one can easily perceive that the data density is drastically higher over the Paris area which is not that obvious with the standard view. Day aircraft trajectory over France (left), and 3D density map (right).