An Exploration of Techniques to Improve Relative Distance Judgments within an Exocentric Display

Chapter 1: Introduction

1.1 Attaining Situation Awareness within Virtual Environments

Loss of situational awareness is a major contributing factor to the occurrence of mishaps when individuals are performing a specific mission or task. The ability of a pilot, for example, to maintain situation awareness has been recognized for some time in the aviation psychology community as crucial to mission success and survivability (Endsley, 1988; Alkov, 1994). Thus, a need exists to more effectively communicate situation awareness to individuals so that they can more successfully accomplish a specific mission. One of the main objectives of this research is to develop more effective approaches for communicating situation awareness. Specifically the project is investigating the use of virtual (computer-generated) interfaces and environments as a means for rapidly communicating mission critical information to those involved.

Situation awareness consists of several components, including spatial awareness. Spatial awareness refers to an individual's understanding of the three-dimensional (3D) geometry of a particular environment. The need for adequate spatial awareness can range from military mission applications, where understanding the relative position of allies and enemies is important, to medical applications where understanding the relative location of organs and tumors within the environment of a human body is critical. In general, spatial awareness becomes vital when someone needs to understand the spatial relationships of elements within an environment in order to effectively accomplish a mission or task. Virtual environment interfaces provide many approaches for representing 3D space and thus may be useful in communicating spatial awareness so that an individual may successfully complete the intended mission.

1.2 Focus of this Research

The perceptual understanding of 3D space, in the natural world, comes primarily from the use of specific visual cues for depth and distance. With current computer technologies, many of these cues can be recreated in order to augment and partially replicate human perceptual capabilities. Part of this research focuses on the re-creation of several specific depth and distance cues in order to see their effect on relative distance judgments made within a computer-generated 3D space. These cues have yet to be directly compared in order to determine the most effective method for communicating relative spatial relationships among objects. The specific 3D environment of interest used in this research was an exocentric, or god's-eye-view display. In addition to examining the speed and accuracy with which subjects made relative distance judgments, subjective evaluations of distance judgments - such as subject confidence and strategy evaluations - were also taken into consideration when evaluating the benefits of the different techniques.

The goal of this research is to determine each feature's effect on making relative distance judgments so that recommendations can be provided for those individuals designing 3D exocentric spatial displays. The results of this research, however, should be applied within the context of a given application environment. In addition, even if specific computer graphics techniques are beneficial in allowing one to make relative distance judgments more quickly and accurately, there may be computational costs for providing these capabilities. Thus when designing displays, these costs, as well as other application-specific interactions, will need to be weighed against each feature's benefit for performing the intended task.

A non-immersive (desktop stereographic) virtual interface was chosen as the primary platform for this research. This decision was based on the notion that a user of this system, such as a military commander or surgeon, may need to quickly attend to the context outside of the display environment. Thus, it might not be appropriate to have a totally immersive display. This perspective is consistent with the, now current, "open shared workspace" concept in computer supported collaborative work (CSCW). This concept asserts that a workgroup will generally accept a new computer technology or tool only if the current set of work tools can be used simultaneously (Ishii and Miyake, 1991).

1.3 Organization of Thesis

This thesis is organized as follows: First we review the literature for information on issues related to this research. Following the literature review is a description of the methods and findings of each of the three experiments performed. We conclude by discussing the human factors implications of these findings for conveying situation awareness.