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The following paper provides an assessment of how selected properties of a virtual reality system impact size-distance judgments in a virtual environment. Manipulations are made in viewing conditions (biocular vs. stereoscopic), image resolution, field of view, scene contrast, and target distance, while subjects attempt to match the attributes of a comparison object with a standard object. General findings suggest that under more natural viewing conditions, size-distance judgments in virtual environments differ from those found previously in physical environments; whereas, under impoverished conditions, performance differences between the two environments are similar.systems. Each nomograph produces a design trade-off space that reveals ways to make a VR system which achieves a predicted level of human performance in the virtual environment. One aim of our group is to produce design trade-off nomographs of this nature.

Work domain analysis (WDA) is an approach developed by Rasmussen (1985) for representing the structure of complex work environments. Many examples of the approach have surfaced in the literature, predominantly of physically coupled causal systems (e.g., process control). For causal systems, the environment is strongly constrained by the laws of nature. This approach can also be used for representing intentional systems (e.g., military command and control), although there is some controversy on this issue. For intentional systems, the environment is strongly constrained by actors' intentions, values, and priorities of practice. This paper discusses the differences between causal and intentional systems and provides direction on how to proceed with a WDA for intentional systems. A WDA is presented for emergency ambulance dispatch management and military command and control to illustrate the approach. Finally, a discussion of the implications and future research recommendations are presented.

This report has been reviewed by the Office of Public Affairs (PA) and is releasable to the National Technical Information Service (NTIS). At NTIS, it will be available to the general public, including foreign nations. This technical report has been reviewed and is approved for publication.

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