PROVIDING DESTINATION PREVIEW CAPABILITY
Introduction: Providing destination preview capability refers to providing the user with the capability to recenter (slew) the map and to change the range scale (magnification) to enable full preview of route details. The user of an electronic map displaying route information may desire to preview the origin, destination, or any segment of the route. The system design should, however, distinguish clearly between a recentered map mode (i.e., vehicle in center of display) and the normal display mode (i.e., vehicle moves relative to stationary map) showing current position of the user/vehicle. Failure to clearly distinguish between these two modes can result in confusion about current location.
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Design Guidelines**
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Allow ATIS users to preview a detailed depiction of the destination or other key nodes or segments of a planned route. This capability can be provided by the combination of a map recentering (slew) function and a map scale (magnification) function. |
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Function Map Slew/Recenter
Map Scale Control
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Description Car in Center of Display, Geographic Definition, Definition of Map Segment Control of X, Y Scaling in Miles/Kilometers Caution When Not Vehicle-Centered |
Example Implementation Touchscreen, or Joystick, or Trackball
Multistage Toggle Button or Knob, Up and Down Arrows Indicator Light, Recenter Button or Function Available Only When Stopped |
Grand View of Long Route; Detailed View of One Node Recentered
Important Note: The map display depicted above is provided solely to augment this Design Guideline by illustrating general design principles. It may not be suitable for your immediate application without modification.
Supporting Rationale: As described in Reference 1, the utility of electronic maps is multiplied by incorporating the combination of a map scale control and recenter function. The combination of scale control and a recentering function enables the user to preview any area of the map in greater detail. The user can have a Ahigh level@ overview of a long route or a closer look at more detailed features pertinent to turns, areas of potential navigation errors, the destination, or other areas of interest. With the magnified view, the map must be recentered to achieve a detailed view of a more distant map location.
Special Design Considerations: In-vehicle navigation displays typically depict the vehicle near the center of the display screen. When the user recenters the map, the vehicle symbol will no longer be in the normal location relative to the screen. This can lead to user confusion about current vehicle location, particularly if the user=s attention is turned elsewhere after recentering. The benefits derived from empowering users to recenter the map must be weighed against the potential for misinterpretations of current location. Protection against this type of error can be designed into the system by displaying a caution indicator or by locking out the recenter function when the vehicle is in motion. If users are allowed to slew or recenter the map while in motion, a simple one-button return to the normal, user-vehicle-centered mode is recommended. A mode that allows the vehicle to always remain in the center of the screen may also be provided.
Cross References:
Control Movement Compatibility
Key References:
1. Clarke, D. L., McCauley, M. E., Sharkey, T. J., Dingus, T. A., & Lee, J. D. (1996). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: Comparable systems analysis. Washington, DC: Federal Highway Administration (FHWA-RD-95-197).
*Primarily expert judgement
** Expert judgement with supporting empirical data
***Empirical data with supporting expert judgement
****Primarily empirical data