Effects of Resolution, Range, and Image Contrast on Target Acquisition Performance.

OBJECTIVE: We sought to determine the joint influence of resolution, target range, and image contrast on the detection and identification of targets in simulated naturalistic scenes. BACKGROUND: Resolution requirements for target acquisition have been developed based on threshold values obtained using imaging systems, when target range was fixed, and image characteristics were determined by the system. Subsequent work has examined the influence of factors like target range and image contrast on target acquisition. METHOD: We varied the resolution and contrast of static images in two experiments. Participants (soldiers) decided whether a human target was located in the scene (detection task) or whether a target was friendly or hostile (identification task). Target range was also varied (50-400 m). In Experiment 1, 30 participants saw color images with a single target exemplar. In Experiment 2, another 30 participants saw monochrome images containing different target exemplars. RESULTS: The effects of target range and image contrast were qualitatively different above and below 6 pixels per meter of target for both tasks in both experiments. CONCLUSION: Target detection and identification performance were a joint function of image resolution, range, and contrast for both color and monochrome images. APPLICATION: The beneficial effects of increasing resolution for target acquisition performance are greater for closer (larger) targets.

Reference frame congruency in search-and-rescue tasks.

OBJECTIVE: Our aim was to investigate how the congruency between visual displays and auditory cues affects performance on various spatial tasks. BACKGROUND: Previous studies have demonstrated that spatial auditory cues, when combined with visual displays, can enhance performance and decrease workload. However, this facilitation was achieved only when auditory cues shared a common reference frame (RF) with the visual display. In complex and dynamic environments, such as airborne search and rescue (SAR), it is often difficult to ensure such congruency. METHOD: In a simulated SAR operation, participants performed three spatial tasks: target search, target localization, and target recall. The interface consisted of the camera view of the terrain from the aircraft-mounted sensor, a map of the area flown over, a joystick that controlled the sensor, and a mouse. Auditory cues were used to indicate target location. While flying in the scenario, participants searched for targets, identified their locations in one of two coordinate systems, and memorized their location relative to the terrain layout. RESULTS: Congruent cues produced the fastest and most accurate performance. Performance advantages were observed even with incongruent cues relative to neutral cues, and egocentric cues were more effective than exocentric cues. CONCLUSION: Although the congruent cues are most effective, in cases in which the same cue is used across spatial tasks, egocentric cues are a better choice than exocentric cues. APPLICATION: Egocentric auditory cues should be used in display design for tasks that involve RF transformations, such as SAR, air traffic control, and unmanned aerial vehicle operations.

Smooth rotation of 2-D and 3-D representations of terrain: an investigation into the utility of visual momentum.

OBJECTIVE: The potential advantage of visual momentum in the form of smooth rotation between two-dimensional (2-D) and three-dimensional (3-D) displays of geographic terrain was examined. BACKGROUND: The relative effectiveness of 2-D and 3-D displays is task dependent, leading to the need for multiple frames of reference as users switch tasks. The use of smooth rotation to provide visual momentum has received little scrutiny in the task-switching context. A cognitive model of the processes involved in switching viewpoints on a set of spatial elements is proposed. METHODS: In three experiments, participants judged the properties of two points placed on terrain depicted as 2-D or 3-D displays. Participants indicated whether Point A was higher than Point B, or whether Point B could be seen from Point A. Participants performed the two tasks in pairs of trials, switching tasks and displays within the pair. In the continuous transition condition the display dynamically rotated in depth from one display format to the other. In the discrete condition there was an instantaneous viewpoint shift that varied across experiments (Experiment 1: immediate; Experiment 2: delay; Experiment 3: preview). RESULTS: Performance after continuous transition was superior to that after discrete transition. CONCLUSION: The visual momentum provided by smooth rotation helped users switch tasks. APPLICATION: The use of dynamic transition is recommended when observers examine multiple views of terrain over time. The model may serve as a useful heuristic for designers. The results are pertinent to command and control, geological engineering, urban planning, and imagery analysis domains.

Group differences in physician responses to handheld presentation of clinical evidence: a verbal protocol analysis.

BACKGROUND: To identify individual differences in physicians' needs for the presentation of evidence resources and preferences for mobile devices. METHODS: Within-groups analysis of responses to semi-structured interviews. Interviews consisted of using prototypes in response to task-based scenarios. The prototypes were implemented on two different form factors: a tablet style PC and a pocketPC. Participants were from three user groups: general internists, family physicians and medicine residents, and from two different settings: urban and semi-urban. Verbal protocol analysis, which consists of coding utterances, was conducted on the transcripts of the testing sessions. Statistical relationships were investigated between staff physicians' and residents' background variables, self-reported experiences with the interfaces, and verbal code frequencies. RESULTS: 47 physicians were recruited from general internal medicine, family practice clinics and a residency training program. The mean age of participants was 42.6 years. Physician specialty had a greater effect on device and information-presentation preferences than gender, age, setting or previous technical experience. Family physicians preferred the screen size of the tablet computer and were less concerned about its portability. Residents liked the screen size of the tablet, but preferred the portability of the pocketPC. Internists liked the portability of the pocketPC, but saw less advantage to the large screen of the tablet computer (F[2,44] = 4.94, p = .012). CONCLUSION: Different types of physicians have different needs and preferences for evidence-based resources and handheld devices. This study shows how user testing can be incorporated into the process of design to inform group-based customization.