Speed-dependent automatic zooming couples the user's rate of motion through an information space with the zoom level-the faster the user moves the 'higher' they fly above the work surface. Igarashi and Hinckley [2000] proposed using the technique to improve scrolling through large documents. Their informal preliminary evaluation showed mixed results with participants completing scrolling tasks in roughly the same time, or more slowly, than when using traditional methods. In this paper, we describe the implementation and formal evaluation of two rapidly interactive speed-dependent automatic zooming interfaces. The ecologically oriented evaluation shows that scrolling tasks are solved significantly faster with automatic zooming in both text document and map browsing tasks. Subjective preferences and workload measures also strongly favour the automatic zooming systems. Implications for the future of scrolling interfaces are substantial, and directions for further work are presented.
Speed dependent automatic zooming (SDAZ) is a promising refinement to scrolling in which documents are automatically zoomed-out as the scroll rate increases. By automatically zooming, the visual flow rate is reduced enabling rapid scrolling without motion blur. In order to aid SDAZ calibration we theoretically and empirically scrutinise human factors of the speed/zoom relationship. We then compare user performance with four alternative text-document scrolling systems, two of which employ automatic zooming. One of these systems, which we term 'DDAZ', is based on van Wijk and Nuij's recent and important theory that calculates optimal pan/zoom paths between known locations in 2D space. van Wijk and Nuij suggested that their theory could be applied to scrolling, but did not implement or test their formulaic suggestions. Participants in our evaluation (n=27) completed scrolling tasks most rapidly when using SDAZ, followed by DDAZ, normal scrollbars, and traditional rate-based scrolling. Workload assessments and preferences strongly favoured SDAZ. We finish by examining issues for consideration in commercial deployments.
Previous studies indicate that user performance with scrolling can be improved through Speed-Dependent Automatic Zooming (SDAZ), which automatically couples the document's zoom-level with scroll-speed. These studies have compared traditional scrolling techniques (scrollbars and rate-based scrolling) with SDAZ, leaving a potential confound that the efficiency gains are due to zooming rather than the automatic binding of zoom-level with speed. It is therefore possible that decoupling zoom from speed, allowing users separate but concurrent control of each, could further enhance performance. This paper describes an experiment (n=35) that examines user performance, workload, and preference in tasks that involve scroll-based acquisition of off-screen targets using SDAZ and manual zooming. Three different types of document navigation are explored: text documents, 'flat' 2D maps, and a 'globe browser' that allows multi-level zooming of a globe-map of Earth and underlying city views. Results show that automatic zooming not only improves performance, but that it does so with substantially less subjective workload, and that it is strongly preferred. We also confirm limited previous work using Fitts' Law as a model for off-screen target acquisition, and show that it applies even when zooming is employed.
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