Nonrigid environments, such as the human colon, present unique challenges in maintaining spatial orientation during navigation. This paper presents a design concept for presenting spatial information in an augmented reality (AR) display, together with results of an experiment conducted to evaluate the relative usefulness of three types of spatial information for supporting navigation and spatial orientation in a nonrigid environment. Sixteen untrained subjects performed a simulated colonoscopy procedure, using rigid and nonrigid colon models and six different AR displays comprising various combinations of direction, location, and shape information related to the scope inside the colon. Results showed that, unlike navigating in rigid environments, subjects took 44% longer to navigate the nonrigid environment and were less efficient, and suggested that it may be useful to train aspiring endoscopists in an equivalent rigid environment initially. A navigational aid presenting shape information was more beneficial than location or direction information for navigating in the nonrigid environment. Even though the AR navigational aid display did not speed up travel time, navigation efficiency and confidence in direction and location judgment for all subjects were improved. Subjectively, subjects preferred having shape information, in addition to position and direction information, in the navigational aid.

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