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Objective: The effect of viewpoint on the navigation of complex terrain and on spatial awareness was examined with the use of a simulated remotely operated vehicle. Background: The ability to build terrain models in real time may soon allow remote vehicular control from any viewpoint. A virtual tether couples the viewpoint to the vehicle's position and orientation, but shows more of the terrain than a fully immersive egocentric display. In this sense, it provides visual momentum by providing a view that incorporates egocentric and exocentric qualities. Method: For this study, 12 participants navigated a simulated vehicle across complex virtual terrain using five different display viewpoints: egocentric, dynamic tether, rigid tether, 3-D exocentric, and 2-D exocentric. While navigating, participants had to avoid being seen by simulated enemy units. After the navigation task, participants' spatial awareness was assessed using a recognition task. Results: The tethered displays minimized the time during which the participant's vehicle was visible to enemy positions. The egocentric display was more effective than exocentric displays (2-D or 3-D) for navigation, and the exocentric displays were more effective than egocentric for time seen during navigation and the recognition task. The tethered displays produced intermediate results for navigation and recognition. Conclusion: Viewpoint tethering produced the most effective displays for minimizing time seen, but tethered displays were less effective than egocentric and exocentric displays for navigation and recognition, respectively. Application: A tethered display is recommended for applications in which it is necessary to understand the relation of nearby locations to one's own location.

Objective: We examined the effects of aid reliability and reliability disclosure on human trust in and reliance on a combat identification (CID) aid. We tested whether trust acts as a mediating factor between belief in and reliance on a CID aid. Background: Individual CID systems have been developed to reduce friendly fire incidents. However, these systems cannot positively identify a target that does not have a working transponder. Therefore, when the feedback is "unknown", the target could be hostile, neutral, or friendly. Soldiers have difficulty relying on this type of imperfect automation appropriately. Method: In manual and aided conditions, 24 participants completed a simulated CID task. The reliability of the aid varied within participants, half of whom were told the aid reliability level. We used the difference in response bias values across conditions to measure automation reliance. Results: Response bias varied more appropriately with the aid reliability level when it was disclosed than when not. Trust in aid feedback correlated with belief in aid reliability and reliance on aid feedback; however, belief was not correlated with reliance. Conclusion: To engender appropriate reliance on CID systems, users should be made aware of system reliability. Application: The findings can be applied to the design of information displays for individual CID systems and soldier training.

Objective: We sought to determine the influence of message presentation rate (MPR) and sensory modality on soldier cognitive load. Background: Soldiers commonly communicate tactical information by radio. The Canadian Army is equipping soldiers with a battle management system (BMS), which also allows them to communicate by text. Method: We varied presentation modality (auditory vs. visual) and MPR (fast or slow) in an experiment involving a tactical scenario. Participants (soldiers) received messages and periodically provided situation reports to higher level command, and the scored reports were used to provide a measure of situation awareness (SA). The detection response task (DRT) and NASA-TLX were used to measure cognitive load. Results: The fast MPR reduced DRT accuracy and increased response times relative to slow MPR. The NASA-TLX results also showed higher subjective workload ratings for several subscales with fast MPR. Messages presented visually produced greater cognitive load, with slower DRT response times for the visual than the auditory condition. SA scores were higher with slower MPR and auditory presentation. There was no statistical interaction of presentation modality and rate for any measure. Conclusion: Fast MPR and visual presentation increased cognitive load and degraded SA. Application: These findings show that the DRT can be used to measure workload effectively in a tactical military context and that the method of information presentation affects how soldiers process information in a BMS.

Objective: We investigated the effects of automatic target detection (ATD) on the detection and identification performance of soldiers. Background: Prior studies have shown that highlighting targets can aid their detection. We provided soldiers with ATD that was more likely to detect one target identity than another, potentially acting as an implicit identification aid. Method: Twenty-eight soldiers detected and identified simulated human targets in an immersive virtual environment with and without ATD. Task difficulty was manipulated by varying scene illumination (day, night). The ATD identification bias was also manipulated (hostile bias, no bias, and friendly bias). We used signal detection measures to treat the identification results. Results: ATD presence improved detection performance, especially under high task difficulty (night illumination). Identification sensitivity was greater for cued than uncued targets. The identification decision criterion for cued targets varied with the ATD identification bias but showed a "sluggish beta" effect. Conclusion: ATD helps soldiers detect and identify targets. The effects of biased ATD on identification should be considered with respect to the operational context. Application: Less-than-perfectly-reliable ATD is a useful detection aid for dismounted soldiers. Disclosure of known ATD identification bias to the operator may aid the identification process.

Objective: The aim of this study was to evaluate display formats for an automated combat identification (CID) aid. Background: Verbally informing users of automation reliability improves reliance on automated CID systems. A display can provide reliability information in real time. Method: We developed and tested four visual displays that showed both target identity and system reliability information. Display type (pie, random mesh) and display proximity (integrated, separated) of identity and reliability information were manipulated. In Experiment 1, participants used the displays while engaging targets in a simulated combat environment. In Experiment 2, participants briefly viewed still scenes from the simulation. Results: Participants relied on the automation more appropriately with the integrated display than with the separated display. Participants using the random mesh display showed greater sensitivity than those using a pie chart. However, in Experiment 2, the sensitivity effects were limited to lower reliability levels. Conclusion: The integrated display format and the random mesh display were the most effective displays tested. Application: We recommend the use of the integrated format and a random mesh display to indicate identity and reliability information with an automated CID system.

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.

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.