Human Factors in the Design of Tactical Display Systems for the Individual Soldier (1995) / Chapter Skim
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3 Helmet-Mounted Display Technology and Human Factors
3 Helmet-Mounted Display Technology and Human Factors
Pages 39-64
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From page 39... ...
The discussion includes consideration of how these devices may enhance or detract from the attention, situation awareness, and workload of infantry soldiers. This discussion complements that of the preceding chapters, which considered the military environment in which the devices will be used and the capabilities and limitations of the soldiers who will use them.
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From page 40... ...
Prominent among the concerns that call for further research and testing are both longand short-term effects of the protracted visual rivalry that results from the use of monocular and biocular displays. It has been suggested that later versions of the display screens may be transparent (Computer Science Corporation, 1993~: transparent displays are now used in some combat aircraft as alternative to a head-down instrument panel, in part to eliminate the time a user would otherwise need to perform the oculomotor actions (saccadic glances, vergence movements, accommodation changes)
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From page 41... ...
In the Land Warrior System, the helmet-mounted display is proposed as a monocular device. This supposedly leaves the other eye unobstructed, but visual rivalry will then occur between the two eyes; this rivalry should be particularly intense if the display is opaque.
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From page 42... ...
even though it was in the field of view. , , A, Second, through excessive fragility, bulk, and weight, the equipment by which remote or sensor information is displayed may seriously reduce the mobility of the dismounted infantryman, and it may add fatigue and heat stress (U.S.
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From page 43... ...
The next section considers venous aspects of the human visual system in relation to displays. The subsequent shorter sections consider situation awareness and workload issues.
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From page 44... ...
These sensory properties are readily measured. However, they do not by themselves provide information on whether the display allows the viewer adequate perceptual knowledge of the objects and layout being confronted and adequate situation awareness of the environment in which the actions are to be taken.
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From page 45... ...
In biocular displays both eyes receive the same augmented view. In binocular displays the two eye's views are disparate so as to provide binocular parallax or stereoscopic depth information, obtained from sensors of fixed vergence.
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From page 46... ...
Infantry School personnel reported to the panel that a number of soldiers had difficulty using the monocular night vision devices. These problems included vomiting, temporary blindness in the unstimulated eye, and temporary total blindness.
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From page 47... ...
are not related in any simple way to the perceptual tasks in which the displays are to be used, we outline the information needed for classes of tasks more generally. We do so first in terms of perceiving what is present in the visual environment and then in terms of situation awareness.
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From page 48... ...
The possibility of creating tables based on the human factors literature will be explored in Phase IT. However, most of the visual tasks that are normally required of infantry soldiers do not depend on information about what contours and points can be distinguished on the ~ .~ ~ r r '.
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From page 49... ...
Resolution, gray scale, and field of view of the transmitted or reconstructed image are always impaired relative to unaided vision; this degrades or eliminates those cues that depend on detail (like textural gradients) , on gradations of shade (like modeling)
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From page 50... ...
. Intermediate depth is normally provided by the visual parallax that arises from body motion and head motion, by linear perspective and its related depth cues (e.g., relative size, textural gradients etc.)
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From page 51... ...
. How Helmet-Mounted Displays Might Affect Depth Information Helmet-mounted displays, like night vision devices, capture optical information about the environment and present it visually to the wearer.
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From page 52... ...
Most familiar classes of objects can be recognized with extreme rapidity even in the absence of any depth information, cued only by their shapes in the display (Biederman, 1985; Peterson et al., 19911. Performance tasks that do not require any specific depth perception-but that can be carried out by recognizing some objectors)
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From page 53... ...
There is presently no single accepted cognitive theory from which one can set the bounds of an individual glimpse. For example, are successive views of a display "directly" placed by the visual system into a single perceptual setting, without passing through any .
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From page 54... ...
ATTENTION AND SITUATION AWARENESS A helmet-mounted display allows visual and auditory information of various kinds to be offered to a wearer, without the major change in gaze or posture that is needed to look down at a map, to raise a viewing or sighting device, or to position an earphone. However, as noted above, various aspects of the proposed electronic displays interfere with a user's ability to direct attention within the visual field, in particular, and within the inflow of information, more generally.
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From page 55... ...
and has direct relevance for the 21st Century Land Warrior System. The reported benefits associated with achieving situation awareness include improved safety, reduced workload, enhanced performance, expanded range of operations, and improved decision making (Regal et al., 1988)
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From page 56... ...
More generally, design of helmet-mounted displays should aim to overcome the main factors that currently limit situation awareness in the particular environments being considered. For example, there may be a need for sensory enhancement by improving a wearer's ability to localize targets and self and to navigate in the environment; keeping a soldier and commander up to date on changes and situation factors in the field; sharing information between team members; distributed decision making across teams and between headquarters and teams; and allowing soldiers to look at information in different ways, thus supporting strategic decision making.
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From page 57... ...
High cognitive workload associated with the operation of the 2Ist Century Eared Warrior System may also have a negative impact on users' situation awareness if the requirements exceed users' capacity to process information (Taylor, 1990; Adams et al., in press; Endsley, 19931. Table 3-2 lists some of the situation awareness issues that need to be considered in design trade-off studies.
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From page 58... ...
| Integration of helmet- Attentional narrowing under mounted display cues with high task load or stress may external events providing result in fixation on information fusion displays, interrupting attention switching to environment | Expansion of area and time Trained information frame over which attention sampling strategies and scan is distributed patterns may be disrupted by stress and high task load ~(Wickens, 1992) | Attention to some elements of situation may result in decrease in SA on other elements (Fracker, 1989; Endsley, in press)
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From page 59... ...
| Factor l Benefit | Cost Working Memory | Direct presentation of | Extra cognitive tasks and needed information may task complexity imposed by support limited working system can seriously memory overload limited working memory, restricting situation awareness and decision making, | I particularly under stress I | nformation overload may occur wherein the amount of information present exceeds the amount the user can take in, threatening appropriate prioritization of | ~ information Information ~ Provides more accurate, up- ~ Information overload will to-date information to pose new sorting and soldiers in field, and back to processing demands I headquarters from field l l Provides information in a | n formation presented that different format that may be is not consistent with more compatible with user soldier needs will slow needs (e.g., updated map down processing of instead of audio description, important information | egocentric map instead of | l L exocentric) l l l Enhanced sensory | nformation that must be information (e.g., targeting integrated or processed to support, night vision)
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From page 60... ...
There is some evidence concerning dual-task performance or time-sharing capabilities, but these have not been examined in association with physical effort. CONCLUSIONS Information provided through a helmet-mounted display cannot, in the current stateof-the-art, be used by a human observer as rapidly and as effectively, with the same situation awareness, and with the same sense of presence as is achieved with normal visual dentin · ~ .~ ~ ~ 1 cues.
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From page 61... ...
conclitions-in orcler to evaluate the potential for increaser' workload and for loss of situation awareness on the part of the soldier. The research plans should also include procedures for detecting design features that might support situation awareness by directing the soldier's attention to salient aspects of situations that otherwise might be missed.
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From page 62... ...
Yet helmet-mounted displays can aid situation awareness by improving a wearer's ability to localize targets and self, to navigate in the environment, to keep up to date on situational factors, and to share information among team members.
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From page 63... ...
As we move into the second phase of our work, we will continue to examine the features of displays that relate to human perceptual, cognitive, and physiological characteristics. Moreover, we will further explore the impact of various technologies on situation awareness and cognitive workload for soldiers performing infantry tasks in a team context.
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