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In addition to these elements of display quality are also elements related to presentation on a given display. Many techniques have been employed to overcome the problem of lack of space when using devices with small displays. The following elements become central to usability concerns as display size gets smaller:

• Presentation: what is presented and what isn’t (e.g. peephole displays, ‘halo’ etc.) and how

• Text/Reading: line length, text splitting, guided scrolling, RSVP, etc. • Interaction: methods users use to interact with the system

• Navigation: features added to improve movement within and among visual elements

• Design: use of color, shape and layering to improve intuitive interaction with perceptual layers

Early work focusing on display size looked at text presentation. Still there is a great deal of effort going into how people read text and how best to present it on a display. From testing text presentation on paper versus that on a display to line length (Bernard, Fernandez and Hull, 2002) and the use of Rapid Serial Visual Presentation (RSVP) (Bernard, Chaparro and Russell, 2000) and beyond, HCI and cognition researchers have made significant contributions to understanding what makes a

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readable display. The heterogeneity of display sizes alone has made ways in which to interface with them more challenging.

Perhaps the real challenge/opportunity comes in the area of image manipulation. A great deal of work has been done on digital displays and image quality in the medical arena and in viewing radiologic images in particular. In Hemminger, Bauers and Yang (2008), emphasis was placed on comparing navigation techniques for large digital images. Five interaction styles were investigated: scroll bar, mag lens, pointer, arrow key and sectional. They found that the pointer interaction was preferred over all others and was described by subjects as being most intuitive and ‘mimicked net searching.’ In studies of 3D models and medical images, and their rendering on mobile devices, a central question revolves around the detail required for the task at hand, and, presumably, for the task ‘in the field.’

Lots of work is being done to investigate support of remote health care work and particularly the transmission of high quality radiologic information (Andrade,

Wangenheim and Bortoluzzi, 2003). This focus on data transmission and/or manipulation (Tang, Law, Lee and Chan, 2004) of image information rather than of visualization has met with some success (Correa, Ishikani, Ziviani, and Faria, 2008; Toomey et al., 2010). Perhaps more interesting is work involving diagnostic algorithms to support the data collection process in the field and to enhance the medical process by reducing time required for transmission and interpretation (Correa et al., 2008).

There have been many different approaches to handling large image navigation issues in the desktop environment. This is even more of a factor among mobile devices. Early work done by Yee (2003) on Peephole displays demonstrated an approach that would allow the user to view the context of the information space in an offset

superimposed image while at the same time taking action in the main display window. Study findings yielded significant improvements in one-handed tasks using the Peephole display.

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Baudisch and Rosenholtz (2003) introduced their ‘Halo’ concept which helps the user infer the locations of off screen objects with portions of onscreen ‘rings’ (visual references to off screen objects), thereby increasing the visual spatial range of a small display. For users of mobile devices, one of the biggest issues with context is display size. Because large images, maps, web pages, etc. are viewable using small screens and restructuring the information space is not always an option, a great deal of work has gone into optimizing interaction for viewing and interacting with them.

Jones, Jones, Marsden, Patel & Cockburn (2005) investigated speed-dependent automatic zooming (SDAZ), which combines panning and zooming into a single

operation, on small displays. Recommended for improved navigation of large images on desktop systems, SDAZ was presumed to also be effective with small display devices. Their results suggest that, despite requiring fewer actions, use of SDAZ was not faster than using the standard interaction for tasks and that target acquisition was not more accurate. Subjects performed better on map tasks using SDAZ than on document tasks.

Chittaro (2008) conducted an experiment comparing three techniques for navigating large information spaces (maps, webpages). They compared the use of a DoubleScrollbar (standard combination of two scrollbars for separate horizontal and vertical scrolling with zoom buttons to change the scale of the information space), Grab&Drag (which enables users to navigate directly, dragging the currently displayed portion of the information space with zooming handled through a slider control) and Zoom-Enhanced Navigator (ZEN, which is an extension and adaptation to mobile screens of Overview&Detail approaches, which are based on displaying an overview of the

information space together with a detail view of a portion of that space). Their findings suggest that factors like interactive update, sequential versus non-sequential navigation, navigation parameters, orientation cues, and user workload all play an important role in selection and preference of navigation techniques.

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In his work on mobile visualization design, Chittaro (2006) suggests the following six steps when creating visualization designs for the mobile environment: mapping, selection, presentation, interactivity, human factors and evaluation. Chittaro also suggests that the traditional desktop solutions to presentation problems,

overview+detail and focus+context, do not work in mobile environments. Instead, references to off screen information and more intuitive navigation techniques are required. Sensors that provide context or physiological awareness integrated into devices, particularly mobile devices, can provide enhanced information access that may supplement what is not achievable in a small sized display (Chittaro, 2008).

Another important newer area of research is that of immersive or virtual reality environments. What is significant in these environments is a change on the level of interaction which enhances the interface between computing device and human being. Hwang, Joong and Kim (2006) conducted a study comparing perceived field of view among a variety of display sizes with sense of immersion and presence. Their findings, shown in Figure 1—2, suggest that, given a level of interaction with the device that involves motion, the perceived field of view with a small (handheld) device was much greater (50%) than actual.

Figure 1-2. Perceived FOV (marked by subjects). Left is the perceived and right is the actual. Reprinted from “Hand-held Virtual Reality: A Feasibility Study,” by Hwang, J., Jung, J., & Kim, G. J., (2006), VRST '06: Proc. ACM Symp. on Virtual Reality Software and Technol., pp. 356-363. Copyright 2006 ACM Press. Reprinted with permission.

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