![Key elements in Munzner's what-why framework. (a) data abstraction: four basic dataset types; (b) task abstraction: actions and target of tasks. Figures derived from [140, Chap. 2, 3] under CC BY-4.0 Licence.](https://www.researchgate.net/profile/Yalong-Yang-2/publication/330132882/figure/fig5/AS:711691859939328@1546691970887/Key-elements-in-Munzners-what-why-framework-a-data-abstraction-four-basic-dataset_Q320.jpg)
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Visualising Geographically-Embedded Origin-Destination Flows: in 2D and immersive environments
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This thesis develops and evaluates effective techniques for visualisation of flows (e.g. of people, trade, knowledge) between places on geographic maps. This geographically-embedded flow data contains information about geographic locations, and flows from origin locations to destination locations. This thesis explores the design space of OD flow visualisation in both 2D and immersive environments. We do so by creating novel OD flow visualisations in both environments, and then conducting controlled user studies to evaluate different designs.
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... Only recently have researchers begun to systematically investigate immersive geospatial data visualisation [21]. Yang et al. explored immersive visualisation of origin-destination flow maps [6] and of maps and globes in virtual reality [5], [22]. They found clear benefits for the use of 3D representations. ...
We introduce Tilt Map, a novel interaction technique for intuitively transitioning between 2D and 3D map visualisations in immersive environments. Our focus is visualising data associated with areal features on maps, for example, population density by state. Tilt Map transitions from 2D choropleth maps to 3D prism maps to 2D bar charts to overcome the limitations of each. Our paper includes two user studies. The first study compares subjects' task performance interpreting population density data using 2D choropleth maps and 3D prism maps in virtual reality (VR). We observed greater task accuracy with prism maps, but faster response times with choropleth maps. The complementarity of these views inspired our hybrid Tilt Map design. Our second study compares Tilt Map to: a side-by-side arrangement of the various views; and interactive toggling between views. The results indicate benefits for Tilt Map in user preference; and accuracy (versus side-by-side) and time (versus toggle).
... Only recently have researchers begun to systematically investigate immersive geospatial data visualisation [21]. Yang et al. explored immersive visualisation of origin-destination flow maps [6] and of maps and globes in virtual reality [5], [22]. They found clear benefits for the use of 3D representations. ...
In this paper, we present our analysis of five expert interviews, each from a different application domain. Such analysis is crucial to understanding the real-world scenarios of analysing geographically-embedded flow data. The results of our analysis show that similar high-level tasks were conducted in different domains. To better describe the targets of these tasks, we proposed three flow-targets for analysing geographically-embedded flow data: single flow, total flow and regional flow.
In this paper, we present our analysis of five expert interviews, each from a different application domain. Such analysis is crucial to understanding the real-world scenarios of analysing geographically-embedded flow data. The results of our analysis show that similar high-level tasks were conducted in different domains. To better describe the targets of these tasks, we proposed three flow-targets for analysing geographically-embedded flow data: single flow, total flow and regional flow.
This paper presents DXR, a toolkit for building immersive data visualizations based on the Unity development platform. Over the past years, immersive data visualizations in augmented and virtual reality (AR, VR) have been emerging as a promising medium for data sense-making beyond the desktop. However, creating immersive visualizations remains challenging, and often require complex low-level programming and tedious manual encoding of data attributes to geometric and visual properties. These can hinder the iterative idea-to-prototype process, especially for developers without experience in 3D graphics, AR, and VR programming. With DXR, developers can efficiently specify visualization designs using a concise declarative visualization grammar inspired by Vega-Lite. DXR further provides a GUI for easy and quick edits and previews of visualization designs in-situ, i.e., while immersed in the virtual world. DXR also provides reusable templates and customizable graphical marks, enabling unique and engaging visualizations. We demonstrate the flexibility of DXR through several examples spanning a wide range of applications.
Immersive virtual- and augmented-reality headsets can overlay a flat image against any surface or hang virtual objects in the space around the user. The technology is rapidly improving and may, in the long term, replace traditional flat panel displays in many situations. When displays are no longer intrinsically flat, how should we use the space around the user for abstract data visualisation? In this paper, we ask this question with respect to origin-destination flow data in a global geographic context. We report on the findings of three studies exploring different spatial encodings for flow maps. The first experiment focuses on different 2D and 3D encodings for flows on flat maps. We find that participants are significantly more accurate with raised flow paths whose height is proportional to flow distance but fastest with traditional straight line 2D flows. In our second and third experiment we compared flat maps, 3D globes and a novel interactive design we call MapsLink, involving a pair of linked flat maps. We find that participants took significantly more time with MapsLink than other flow maps while the 3D globe with raised flows was the fastest, most accurate, and most preferred method. Our work suggests that careful use of the third spatial dimension can resolve visual clutter in complex flow maps.
Visualizing 3D trajectories to extract insights about their similarities and spatial configuration is a critical task in several domains. Air traffic controllers for example deal with large quantities of aircrafts routes to optimize safety in airspace and neuroscientists attempt to understand neuronal pathways in the human brain by visualizing bundles of fibers from DTI images. Extracting insights from masses of 3D trajectories is challenging as the multiple three dimensional lines have complex geometries, may overlap, cross or even merge with each other, making it impossible to follow individual ones in dense areas. As trajectories are inherently spatial and three dimensional, we propose FiberClay: a system to display and interact with 3D trajectories in immersive environments. FiberClay renders a large quantity of trajectories in real time using GP-GPU techniques. FiberClay also introduces a new set of interactive techniques for composing complex queries in 3D space leveraging immersive environment controllers and user position. These techniques enable an analyst to select and compare sets of trajectories with specific geometries and data properties. We conclude by discussing insights found using FiberClay with domain experts in air traffic control and neurology.
This paper explores different ways to render world-wide geographic maps in virtual reality (VR). We compare: (a) a 3D exocentric globe, where the user’s viewpoint is outside the globe; (b) a flat map (rendered to a plane in VR); (c) an egocentric 3D globe, with the viewpoint inside the globe; and (d) a curved map, created by projecting the map onto a section of a sphere which curves around the user. In all four visualisations the geographic centre can be smoothly adjusted with a standard handheld VR controller and the user, through a head-tracked headset, can physically move around the visualisation. For distance comparison exocentric globe is more accurate than egocentric globe and flat map. For area comparison more time is required with exocentric and egocentric globes than with flat and curved maps. For direction estimation, the exocentric globe is more accurate and faster than the other visual presentations. Our study participants had a weak preference for the exocentric globe. Generally the curved map had benefits over the flat map. In almost all cases the egocentric globe was found to be the least effective visualisation. Overall, our results provide support for the use of exocentric globes for geographic visualisation in mixed-reality.
Immersive technologies such as augmented reality devices are opening up a new design space for the visual analysis of data. This paper studies the potential of an augmented reality environment for the purpose of collaborative analysis of multidimensional, abstract data. We present ART, a collaborative analysis tool to visualize multidimensional data in augmented reality using an interactive, 3D parallel coordinates visualization. The visualization is anchored to a touch-sensitive tabletop, benefiting from well-established interaction techniques. The results of group-based, expert walkthroughs show that ART can facilitate immersion in the data, a fluid analysis process, and collaboration. Based on the results, we provide a set of guidelines and discuss future research areas to foster the development of immersive technologies as tools for the collaborative analysis of multidimensional data.
In movement data analysis, there exists a problem of comparing multiple trajectories of moving objects to common or distinct reference trajectories. We introduce a general conceptual framework for comparative analysis of trajectories and an analytical procedure, which consists of (1) finding corresponding points in pairs of trajectories, (2) computation of pairwise difference measures, and (3) interactive visual analysis of the distributions of the differences with respect to space, time, set of moving objects, trajectory structures, and spatio-temporal context. We propose a combination of visualisation, interaction, and data transformation techniques supporting the analysis and demonstrate the use of our approach for solving a challenging problem from the aviation domain.
Classic geospatial network visualization tends to limit itself to 2D representation by organizing edges and nodes on a 2D map or the external surface of a traditional 3D globe model. Visual clutters and occlusions due to edge crossings and node-edge overlaps make efficient and effective exploration of geospatial networks a challenge. This paper proposes an interactive visualization approach for the intuitive exploration of geospatial networks inside a spherical virtual reality environment. To reduce visual clutter and reveal network patterns, we also propose a parameterized 5-step 3D edge-bundling algorithm and a set of techniques to avoid collision of network edges with the viewpoint. Our spherical interaction and 3D edge-bundling approach have been implemented in an Oculus Rift VR system. We demonstrate the usefulness of our approach with two case studies on real-world network data and usability experiments.
Rupture risk assessment is a key to devise patient-specific treatment plans of cerebral aneurysms. To understand and predictthe development of aneurysms and other vascular diseases over time, both hemodynamic flow patterns and their effect on thevessel surface need to be analyzed. Flow structures close to the vessel wall often correlate directly with local changes in surfaceparameters, such as pressure or wall shear stress. Yet, in many existing applications, the analyses of flow and surface featuresare either somewhat detached from one another or only globally available. Especially for the identification of specific bloodflow characteristics that cause local startling parameters on the vessel surface, like elevated pressure values, an interactiveanalysis tool is missing.The explorative visualization of flow data is challenging due to the complexity of the underlying data. In order to find meaningfulstructures in the entirety of the flow, the data has to be filtered based on the respective explorative aim. In this paper, we presenta combination of visualization, filtering and interaction techniques for explorative analysis of blood flow with a focus on therelation of local surface parameters and underlying flow structures. Coherent bundles of pathlines can be interactively selectedbased on their relation to features of the vessel wall and further refined based on their own hemodynamic features. This allowsthe user to interactively select and explore flow structures locally affecting a certain region on the vessel wall and thereforeto understand the cause and effect relationship between these entities. Additionally, multiple selected flow structures can becompared with respect to their quantitative parameters, such as flow speed. We confirmed the usefulness of our approach byconducting an informal interview with two expert neuroradiologists and an expert in flow simulation. In addition, we recordedseveral insights the neuroradiologists were able to gain with the help of our tool.