Highlighting Techniques to Support Geovisualization Anthony C. Robinson GeoVISTA Center, Department of Geography, The Pennsylvania State University arobinson@psu.edu Abstract One often cited advantage of coordinated geovisualizations is that users are able to quickly view data elements from multiple perspectives. This is typically supported by providing a special visual cue during rollover on a data element. This cue, commonly called highlighting, can be defined as the transient visual effect that is applied on data items across views when a mouse cursor or other input device has moved overhead. Visual highlighting techniques have been largely unexplored in research on coordinating multiple views. Today, virtually all visualization environments rely on simple color-based highlighting styles. This paper offers a typology of five visual highlighting styles, as well as a typology of four interactive highlighting behaviors that are promising for future development. Keywords---, Highlighting, Linked Brushing, Indication, Geovisualization Introduction Defining highlighting is a challenge because there is little agreement across the literature in geovisualization and information visualization. Becker and Cleveland’s (1987) work on brushing scatterplots defines a strategy called transient paint in which data chunks across views are painted with a special color whenever a brush is overhead. In geovisualization literature this technique is sometimes called indication (MacEachren et al. 2003) where it has been described as “…transient picking, as in a mouse-over.” Contemporary information visualization research suggests the term highlighting for this transient visual link across views (Seo and Shneiderman 2004; Ware and Bobrow 2005). For this research, the term is used to describe the transient visual effect that is applied on data items across views when a mouse cursor or other input device has moved overhead. This paper presents a typology of five visual styles of highlighting. Each method is described in detail and graphical examples in the form of mockups are provided. These styles are then described in terms of four interactive behaviors through which they may be presented to users. Motivation Exploring and extending highlighting methods is worth pursuing because they may prove necessary in order for analysts to take advantage of increasingly complicated geovisual displays. In current practice, highlighting is most-commonly limited to a single colored overlay on the visual display. The coordinated highlighting inherent in visualizations serves as the visual dynamic gateway to multivariate data, and therefore it is important to ensure that the design of the