Animated sequences of raster images that represent continuously varying surfaces, such as a temporal series of an evolving landform or an attribute series of socio-economic variation, are often used in an attempt to gain insight from ordered sequences of raster spatial data. Despite their aesthetic appeal and condensed nature, such representations are limited in terms of their suitability for prompting ideas and offering insight due to their poor information delivery and the lack of the levels of interactivity that are required to support visualization. Cartographic techniques aim to assist users of geographic information through processes of abstraction, by selecting, simplifying, smoothing and exaggerating when representing an underlying spatial data set graphically. Here we suggest a number of transformations and abstractions that take advantage of these techniques in a specific context–that of addressing the limitations associated with using animated raster surfaces for visualization, and propose them in the context of a framework that can be used to inform practice. The five techniques proposed are spatial and attribute smoothing, temporal interpolation, transformation of the surfaces into a network of morphometric features, the use of a graphic lag or fading and the employment of techniques for conditional interactivity that are appropriate for visualization. These efforts allow us to generate graphical environments that support visualization when using animated sequences of images representing continuous surfaces and are analogous to traditional cartographic techniques, namely, smoothing and exaggeration, simplification, enhancement and the various issues of design. By developing a framework for considering cartography in support of visualization from this particular type of data and phenomenon we aim to highlight the utility of a generically cartographic approach to information visualization. A number of particular techniques originating from computer science and conventional cartography are used in an application of the framework. A suitably interactive software tool is offered for evaluation–to establish the results of applying the framework and demonstrate ways in which we may augment the visualization of dynamic raster surfaces through animation and more generally aim to offer opportunity for insight through cartographic design.
Methods and Tools for Visualization of Graphs and Graph Algorithms
