Evaluation of the Encoding of Quantitative Data in Multitemporal Maps Based on Spatial Unit Sizes

With the increasing demand and availability of multi-temporal data also the demand for usable multi-temporal maps is growing. Considering conventional cartographic methods such as small multiples or animations, however, a variety of
perceptual problems arise due to viewing time and/or space limitations. Apart from this, only little research has been undertaken in order to find out whether the encoding of change information can also contribute to an improved recognition
of changes from maps. Considering quantitative data, such an encoding is typically realized with adapted lightness or saturation of colours or with graduated symbols.
The goal of this paper is to describe and to empirically evaluate an alternative graphical encoding – namely, the adjustment of the size of spatial units (typically, enumeration units) according to the change of numerical values.