Effects of Head Mounted Display Clutter, Transparency, and Optical Distance on Human Performance During Nautical Navigation

Abstract

Head Mounted Displays (HMDs) are increasingly proposed as a solution designed to reduce costly visual scanning in transportation systems such as cars, planes, and boats. The advantages of HMD platforms are obvious and intuitive. Operators can maintain “eyes out” on the scene in front, to avoid hazards and obstacles, while still processing and monitoring critical display information related to navigation and vehicle operations, as well as communication displays, notifications, and chat boxes, with reduced visual scanning between the display and the world beyond. However, HMD interface clutter, transparency, and optical depth are crucial factors that may impair human performance. This thesis explores the impact of these three HMD interface parameters in nautical navigation tasks. 54 participants across two experiments performed a realistic nautical navigation task in a virtual environment with obstacles, navigating a small speedboat while observing navigational information via an HMD interface. The display interface was varied according to three factors: the amount of information shown (HMD clutter), the optical distance of the information from the user’s eye (2 meters vs. 10 meters), and two opacity settings (low and high), which adjusted the trade-off between the clarity of virtual elements on the display and the visibility of the real-world scene viewed through the HMD. Environmental clutter was manipulated by varying the number of low-salient objects that pose navigational hazards, including mines, wooden boxes, planks, barrels, and logs, as well as other objects that present navigation challenges. Participants were evaluated on task completion time, distance traveled to reach the endpoint, proximity to obstacles, and mental demand. Results showed that participants completed the task more quickly when the number of islands increased, particularly in transparent displays. They also performed the task with shorter distances when the display was positioned at a near optical distance and was highly cluttered. Hazard proximity increased as the number of islands in the environment grew while navigating highly cluttered scenes, especially in opaque displays. Increased proximity to hazards occurred in two ways: when the display was opaque and highly cluttered, and highly clutter environment and near optical distance display. Mental demand followed the same pattern as completion time. This provides a foundation on which more work can ask more complex questions about these relationships and their impact on navigational efficiency.