Evaluation of alternative waveforms for animated mimic displays.

Animated mimic displays can be used to present system information regarding physical form, function, and causality. However, a potential limitation in current designs has been identified: the presence of ambiguous apparent motion. Two theoretical explanations of ambiguous apparent motion are discussed (Fourier and correspondence hypotheses). Two alternative designs (stair-step and approximate sinusoid luminance waveforms) were evaluated. The velocity matches obtained in Experiment 1 indicate that the sinusoidal waveform produced significantly better performance for both accuracy and latency than the stair-step waveform. The velocity estimates obtained in Experiment 2 indicate that ambiguous apparent motion was not visible with the sinusoidal waveform, but was with the stair-step waveform. One of the two hypotheses (correspondence) provides a reasonable fit with the obtained velocity estimates. A fundamental goal in the design of animated mimic displays is to provide unambiguous mappings between perceived velo city and actual flow rates. Critical factors in design (e.g., waveform, chromatic/luminance contrast, spatial/temporal frequency) are discussed. Actual or potential applications of this research include the design of more effective animated mimic displays. INTRODUCTION Advances in computer technology have given system designers powerful tools that can be used to improve the quality of overall system performance. One such tool is graphics display technology, which can be used to improve decision making and problem solving through the provision of alternative conceptual perspectives or "views" of an underlying system. For example, operators must often collect and integrate scattered data that testify about higher-level goals, properties, and constraints. Properly designed configural displays (sometimes referred to as object displays) will assist the individual in completing these tasks (e.g., Bennett, Nagy, & Flach, 1997). In addition, observers must consider the physical characteristics of a system. Displays that are used to represent this type of system information are often referred to as mimic displays, presumably because they mimic the physical structure of the system (e.g., Hawkins, Reising, & Gilmore, 1983a, 1983b; Hollan, Hutchins, McCandless, Rosenstein, & Weitzman, 1987; Hollan, Hutchins, & Weitzman, 1984). An example from Hawkins et al. (1983b) is provided in Figure 1. This mimic display provides a schematic of the fuel system in an advanced fighter aircraft, including the physical location of each tank, the level of fuel within a tank, the physical connections between tanks, and the associated valves to control flow. In terms of the Rasmussen, Pejtersen, and Goodstein (1994) abstraction hierarchy, mimic displays provide information at the level of "physical processes and activities." This "is the level at which physically limiting properties are represented and at which causes of malfunctions are typically identified. Physical changes in components have functional consequences that propagate up through the levels of abstraction" (Rasmussen, 1986, p. 17). Thus a potential benefit of mimic displays is the provision of support for fault detection and compensation tasks. These tasks include (a) detecting the fault; (b) identifying the type, location, and consequences of the fault; (c) identifying alternative resources that can be used to correct the fault; and (d) compensating for the fault by completing the required control inputs. The potential benefits are apparent in the following example using the system depicted in Figure 1. To maintain the proper aerodynamics of an aircraft with multiple fuel tanks, the total amount of fuel within the system must be distributed among the various tanks appropriately. Imagine that there is a stuck valve in this system, causing the center of gravity to change and therefore impairing flight and maneuver-ability. …