A Framework for Augmenting the Visualization of Dynamic Raster Surfaces

Abstract

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.

Space, time and visual analytics

“…Volume rendering techniques are used to visually represent the results (Demšar and Virrantaus 2010). Another way of transforming movement data is deriving a series of continuous surfaces, which are further abstracted to networks of topological features: peaks, pits, channels, ridges, and saddles (Rana and Dykes 2003). This method may be particularly suitable for pre-processing graphics to be used in animations.…”

Digital representation of park use and visual analysis of visitor activities

“…Once the animation stops, additional detail such as overlaid dot maps can provide more information on the current situation. Alternatively, extracting features from surfaces can be another option to reduce graphical complexity (Rana & Dykes, 2003).…”

A Geospatial Mixed Methods Approach to Assessing Campus Safety

“…Compared to other methods for spatial analysis (e.g., Gettis-Ord Gi* and point density analysis), KDA minimizes the effect of unbalanced sample distribution by fitting a weight function at each data point. Additionally, the smoothing effect of KDA allows for better data visualization (Maciejewski et al 2010; Rana and Dykes 2003). Recognizing that perceived risk might vary significantly by the time of day, analyses were stratified by time .…”