Academic journal article Cartography and Geographic Information Science

Do Choropleth Maps Linked with Parallel Coordinates Facilitate an Understanding of Multivariate Spatial Characteristics?

Academic journal article Cartography and Geographic Information Science

Do Choropleth Maps Linked with Parallel Coordinates Facilitate an Understanding of Multivariate Spatial Characteristics?

Article excerpt

Introduction

Many authors claim that geographic visualization (geovisualization) tools with multiple and linked views facilitate the understanding of a complex reality represented by multivariate data sets (e.g., Edsall 2003a; Jem et al. 2007; Ho et al. 2012). If this claim is true, one should expect a wide use of such tools among stakeholder groups who want to reach a better understanding of a multifaceted reality. However, although coordinated and multiple views have been already broadly discussed in the literature, such tools are still rarely used outside academia, and many practitioners are still not aware that multiple linked views might be useful and that coordination can facilitate solving their real-life tasks (Andrienko and Andrienko 2007). We therefore revisit the general issue on whether multiple-view geovisualization tools are useful in order to understand our world. For this purpose, we use multi-hazard assessment and geovisualization as a case.

Strategies in assessing natural-hazard risks have recently evolved toward approaches that integrate the exposure to several hazards with various aspects of vulnerability (Cutter 1996; Cutter, Mitchell, and Scott 2000; Greiving, Fleischhauer, and Luckenkotter 2006; Tate, Cutter, and Berry 2010; Rod et al. 2012; Rod, Opach, and Neset 2014). As a result, there is a demand for visualization tools that mitigation practitioners and decision-makers can use to make sense of multivariate data on hazard exposure and vulnerability (Tate et al. 2011). From this, a novel application domain has emerged, where highly interactive tools with multiple linked map and data displays might be desirable. On the basis of a study on the functionality of a particular web-based geovisualization tool called 'ViewExposed' (Opach and Rod 2013), our aim with this article is to derive more general conclusions on whether multiple-view geovisualization tools consisting of choropleth maps dynamically linked with a parallel coordinate plot (PCP) may facilitate the understanding of multivariate spatial characteristics. More specifically, we have formulated the following three research questions:

(1) Do choropleth maps linked with parallel coordinates help people understand where the most vulnerable locations are and why these locations are vulnerable?

(2) Do parallel coordinates sparklines (small plots the lines of which replicate the polylines from parallel coordinates) help understand the information provided in a PCP?

(3) Might a multiple-view geovisualization approach be intuitive enough to be useful for both expert users and those unfamiliar with sophisticated geovisualization tools?

The article contains six sections. The first section describes the background on geovisualization tools representing multivariate data with an emphasis on the visualization of natural hazards. Thereafter, we introduce the ViewExposed tool and describe briefly its content and dynamic linking functionality. In this context, we also reflect on whether choropleth maps linked with PCPs work. In the third section, we present the empirical study that was carried out in order to verify theoretical considerations. The fourth section provides the data analysis and results. In the last two sections, we discuss the results and conclude.

Background

Cartographic representation of multivariate spatial characteristics

Traditional cartography has mainly considered maps as a medium for effective communication of facts to a wide public. In this traditional approach, however, there are no truly successful solutions for the representation of multivariate spatial characteristics. The use of maps changed significantly in the 1990s (MacEachren 1994; MacEachren and Kraak 1997; Andrienko and Andrienko 1999), when maps became a tool in geovisualization fostering 'visual thinking' (Kraak 1998). Visual thinking has since become a concept encapsulating hypothesis generation and visual data analysis (Andrienko et al. …

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