A series of 3 studies was conducted to test free-modulus magnitude estimation as a measure of perceived presence in virtual environments (VEs) and to model the first- and second-order effects of 11 VE system parameters on perceived presence across 5 subtasks. Sequential experimentation techniques were used to build 4 empirical models using polynomial regression. An integrated empirical model of data combined across 2 experiments demonstrated that all significant factors had a positive effect on perceived presence. Three of these parameters--field of view, sound, and head tracking--had almost 3 times as much influence on presence than the other 4 significant parameters, which were visual display resolution, texture mapping, stereopsis, and scene update rate. Sequential experimentation was an efficient tool for building empirical models of perceived presence, but the subjective nature of this phenomenon and individual differences made data bridging across sequential studies problematic. It was concluded that magnitude estimation is a useful measure of perceived presence, and the resulting polynomial regression models can be used to facilitate VE system design decisions. This research has broad application in the selection and design of VE system components and overall design of VE systems.

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Global Positioning System technology has the potential to revolutionize both commercial and military aircraft landing procedures. It will enable pilots to fly complex, curved approaches rather than the more simple straight-in approaches necessitated by the Instrument Landing System used at most large airports. To complement this technology, Head-Up Display pathway symbology was developed for use in the aircraft to help pilots stay on course during these complex landings. Thirteen Air Force pilots used this pathway symbology in a simulator to land under Visual Meteorological, Partial Instrument Meteorological and Full Instrument Meteorological visibility conditions. Deviations from commanded flight path, as well as lateral and longitudinal deviations from a desired runway touchdown point, were measured. Results indicated that landing performance was acceptable for all pilots and functionally equivalent in all weather conditions. Results of this study suggest that pathway symbology could provide the cues necessary to successfully fly complex, curved approaches to landing. In addition, the merits of using Equivalency Analysis, rather than traditional Analysis of Variance in testing for performance differences is discussed.