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Stefano Burigat and Luca Chittaro
pointing device on the screen with respect to the starting position. Figure 12.3 illustrates the technique. When users start an action by tapping on the map with a pen,
two concentric circles are drawn and their center is the location of the action. As the
user drags the pointing device, a direction line is drawn between the starting position and its current location, indicating the direction of travel. If the pointer remains
within the inner circle, the user is free to scroll within the map in any direction. As
the pointer moves further away from the starting position, the scroll rate increases.
When the pointer moves beyond the inner circle (threshold A in Fig. 12.3), both
zooming and scrolling operations take place. As the user moves closer to the outer
circle (threshold B in Fig. 12.3), the map progressively zooms out and the scroll
speed is modified to maintain a consistent visual flow. When the pointer reaches the
outer circle no further zooming occurs, while scrolling remains active. The rectangle
indicates to the user the area of the map that will be displayed once the navigation
operation is completed. Its size changes proportionally to the current zoom value.
An experimental evaluation showed that the proposed technique reduces the physical navigational workload of users with respect to a standard technique based on the
use of scrollbars, panning, and zoom buttons.
Other techniques to display maps on small screens are based on combining
panning and zooming with compression or distortion and can be classified into
Overview&Detail and Focus&Context techniques.
Overview&Detail techniques provide one or multiple overviews (usually at a
reduced scale) of the whole map, simultaneously with a detailed view of a specific
Fig. 12.3. Illustration of the system proposed by Jones et al. [19] to combine panning and
zooming into a single operation, including control feedback cues (which are emphasized for
clarity). Image courtesy Steve Jones, University of Waikato, NZ
Stefano Burigat and Luca Chittaro
pointing device on the screen with respect to the starting position. Figure 12.3 illustrates the technique. When users start an action by tapping on the map with a pen,
two concentric circles are drawn and their center is the location of the action. As the
user drags the pointing device, a direction line is drawn between the starting position and its current location, indicating the direction of travel. If the pointer remains
within the inner circle, the user is free to scroll within the map in any direction. As
the pointer moves further away from the starting position, the scroll rate increases.
When the pointer moves beyond the inner circle (threshold A in Fig. 12.3), both
zooming and scrolling operations take place. As the user moves closer to the outer
circle (threshold B in Fig. 12.3), the map progressively zooms out and the scroll
speed is modified to maintain a consistent visual flow. When the pointer reaches the
outer circle no further zooming occurs, while scrolling remains active. The rectangle
indicates to the user the area of the map that will be displayed once the navigation
operation is completed. Its size changes proportionally to the current zoom value.
An experimental evaluation showed that the proposed technique reduces the physical navigational workload of users with respect to a standard technique based on the
use of scrollbars, panning, and zoom buttons.
Other techniques to display maps on small screens are based on combining
panning and zooming with compression or distortion and can be classified into
Overview&Detail and Focus&Context techniques.
Overview&Detail techniques provide one or multiple overviews (usually at a
reduced scale) of the whole map, simultaneously with a detailed view of a specific
Fig. 12.3. Illustration of the system proposed by Jones et al. [19] to combine panning and
zooming into a single operation, including control feedback cues (which are emphasized for
clarity). Image courtesy Steve Jones, University of Waikato, NZ