[MyResearch] Refining the notion of Spatial Awareness

Spatial Awareness is one of the component of Situation Awareness (participant's internal model of the situation that involved teamwork): it is the understanding of the location, in 3D space, of particular objects or participants within a given environment. For instance, in a military mission, spatial knowledge is helpful in order to know the relative location of enemy targets, as well as as friendly and neutral players within a given scenario. Spatial awareness involves space perception, i.e., the participant's ability to perceive the 3D layout of an environment. Spatial awareness research is diverse with identified areas including navigation, tracking, cognitive-map development and maintenance, distance perception, and spatial knowledge representation techniques.

We often reduce spatial awareness as location awareness (knowing where objects are in space) but it's a limited definition.

Spatial Knowledge Development/Structure: spatial information gathered by an individual is stored as spatial knowledge. When the spatial environment to be learned is large and can be navigated, this spatial knowledge is often referred to as a cognitive map. However there is some ambiguity in the literature regarding the proper term for spatial information gathered from small-scale, one-room settings (i.e., spatial layout, cognitive map, spatial knowledge). Regardless, studies have shown that environmental context (termed `landmarks' in large-scale environments) aids the development of spatial knowledge, whether that knowledge is of large- or small-scale environments (Venturino & Kunze, 1989; Wickens, 1992).

I try to find: - Barfield, W., Rosenberg, C., and Furness, T. (1995). Spatial Situational Awareness as a Function of Frame of Reference, Virtual Eyepoint Elevation, and Geometric Field of View, SID 93 Digest, pp.107-110. - Venturino, M., and Kunze, R. J. (1989). Spatial Awareness with a Helmet-Mounted Display, Proceedings of the Human Factors Society 33rd Annual Meeting. - Sarter, N.B. & Woods, D.D. (1991). Situation awareness: A critical but ill-defined phenomenon. International Journal of Aviation Psychology, 1, 45-57.

Sarter and Woods (1991) provided an excellent description of the complexities of SA and acknowledged spatial awareness to be one of many contributing factors.

Via Mark Draper:

Spatial Awareness Research:

Venturino and Kunze (1989) investigated the ability to acquire and memorize patterns of spatial locations using a helmet-mounted display (HMD). Their work was based on the premise that human spatial cognition (i.e., spatial awareness) can be measured by the ability to locate, memorize, and replace patterns of spatial locations in an area 240 degrees azimuth by 90 degrees elevation. Thus subjects had to spatialize object locations existing all around them rather then only within a display directly in front of them. This work was an extension of the previous research on spatial awareness performed by Wells, Venturino, and Osgood (1988). The researchers manipulated FOV, number of targets, and availability of context in replacement tasks. The task involved a presentation of a multiple-object environment in which the subject attempted to memorize all object locations. After memorization occurred, the objects were removed and subjects were told to replace specific objects into their original locations.

The results (Venturino & Kunze, 1989) indicate that FOV size affects acquisition of spatial information about one's surroundings, as indicated by an increase of `time to memorize' with decreasing FOVs. Small FOVs require more head movements, more sampling time, and more integration effort to build a mental representation of the spatial environment. Replacement error (i.e., the ability to replace an object back into its original location) was affected not by FOV but by memory load (i.e., number of initial objects). In addition, replacement error was large for targets in the extreme azimuth/elevation locations (95% greater error azimuth, 23% greater error in degrees elevation, as compared to next closest zones). When contextual information was presented in the replacement phase of the study, there was a reduced replacement error for the extreme positions only (52% greater error azimuth, 7% greater error in degrees elevation, as compared to next closest zones).

These results indicate that a large FOV will facilitate the development of spatial awareness. A larger view allows for easier integration of environmental elements and their associated relationships. It also seems that a multiple target environment will adversely affect the development and maintenance of spatial awareness. The finding regarding contextual information is especially interesting. It indicates that the availability of contextual information is of little aid in spatial location recall unless this context is provided at the extreme edge of the FOV. It is precisely in this area that the VB exists, for many viewing conditions. This then offers a potential for the VB to be used as a contextual aid for spatial awareness. Boff and Lincoln (1988) support this notion, stating "egocentric judgment depends upon perceived spatial relations among objects. It is referenced to an "object", although the object may be a part or location of the observer's own body". The availability of context for recall of situation awareness information was also discussed by Sarter and Woods (1991).

Dorighi, Ellis, and Grunwald (1993) also focused on spatial awareness aides for aircraft pilots. They felt that spatial awareness may be positively affected by an inside-out (egocentric) frame of reference primary flight display ("the tunnel in the sky") versus a typical attitude director indicator (ADI). These researchers found that pilot orientation estimates of initial target directions exhibited symmetrical azimuth angle undershoot errors, as was found in earlier research, but there was no effect for display type used.

Much effort has gone into the study of classical depth cues as sources for spatial depth information (Ellis, 1991; McGurk & Jahoda, 1974; Surdick, et al., 1994). These cues can be broken down to object-centered and observer-centered cues (Wickens, 1992). Object-centered cues include linear perspective, interposition, height in the plane, light and shadow, relative size, texture gradients, proximity-luminance covariance, aerial perspective, and relative motion parallax. Observer-centered cues (those that are characteristics of the human visual system) include binocular disparity, convergence, and accommodation. Depth cues are necessary for the perception of 3D space, and the relative effectiveness of each has been extensively researched in the real world. Recently these efforts have expanded into computer displays and VEs (i.e., Ellis, 1991; Surdick, et. al., 1994).

This highlights an important issue regarding spatial awareness and VEs. How well does one's spatial awareness of a virtual environment match the spatial awareness of a similar real (physical) environment? Research in this area is still in its infancy and the results are often contradictory (Hale & Dittmar, 1994; Henry & Furness, 1993; Lampton, Bliss, & Knerr, 1994). It appears that some spatial distortion may be inevitable, due to the lack of certain depth cues such as accommodation. However, one should be cautioned against relying too much on these initial findings, given that these results strongly depend on the particular system used and there is tremendous fidelity variability in VR technology available today.

Spatial Awareness Metrics:

Spatial awareness tasks have involved the use of several different metrics, most of which can be described as being egocentric or exocentric in nature. Venturino and Kunze (1989) used time (seconds) until all object locations were memorized (in search mode) and absolute replacement errors (in degrees error) in a target replacement task, both of which are egocentric. Dorighi, et al. (1993) used body-referenced visual direction to targets in developing mean error in degrees and mean absolute error in degrees. This is also an egocentric measure. Barfield, Rosenberg, and Furness (in press) utilized an alternate metric that followed an egocentric spatial display with a test using an exocentric map. Subjects flew a flight simulation that involved a search for several stimuli. After the flight, spatial knowledge was tested by having the subjects locate each stimulus on an exocentric map of the entire area (evaluating mean horizontal and vertical offset errors). A variation of this technique used by Marshak, Kuperman, Ramsey, and Wilson (1987) involves stopping the simulation at various points to probe subjects on the relative positions of targets. The dependent variable was the absolute percent error for each question summed for all questions in a trial. A final metric, developed by Palmer (1990), adapts standard psychophysical methods to measuring position in a multi-stimulus display. Subjects are presented with an egocentric spatial environment, then with a test condition that is similar except that one target has been displaced in some way. The subject, cued as to the identity of the displaced target, must state how the target has been displaced (up-down, left-right, forward-back). From these data, a psychometric function can be constructed and a difference threshold estimated for position.

McNamara (1986) presented a list of major spatial awareness/spatial representation metric categories. The list is as follows: distance estimation, orientation judgments, map drawing, navigation, and search/replace tasks. Often the choice of metric category depends on the particular aspect of spatial awareness being studied.

Since distance estimation is used in many spatial awareness studies, a brief background of this metric is in order. Distance estimation can be absolute (i.e., distance from the observer to an object) or relative (i.e., distance between two objects or other people). Absolute distance could also be termed egocentric distance and relative distance could be termed exocentric distance.

Under natural, unrestricted viewing conditions, the perception of distance is remarkably consistent (Baum & Jonides, 1979, Boff & Lincoln, 1988). Baird and Biersdorf (1967) as well as others have showed that the relationship of perceived distance and actual distance, on average, can be described by a power function:


where k and n are constants for that location/orientation, J is the judged distance, and D is the actual distance. The exponent `n' approximates 1.0 overall; it is generally slightly greater then 1.0 with indoor observation and generally less then 1.0 with outdoor observations (Da Silva and Fukusima, 1986).

Research has shown that large individual differences exist in judgment of apparent distance (Cook, 1978; Da Silva & Fukusima, 1986). However, Da Silva and Fukusima (1986) found that these individual differences, manifest in individual exponents of each fitted power function for magnitude estimation of apparent distance, remain stable regardless of environment (natural indoor or natural outdoor), range of distances estimated, and length of the inter-session interval, for up to 9 months. It is reasonable, then, to use a within-subjects design for distance estimation-type activities. This design style would negate the effects of large individual differences observed in distance estimation while maintaining the observed temporal stability found within each individual's judgments.

Spatial awareness could also be measured indirectly through techniques designed to measure SA. One such technique is Situation Awareness Global Assessment Technique (SAGAT) (Endsley, 1988). SAGAT involves stopping a task at random intervals so that the subject can be asked a question that relates to his/her SA at that time (not unlike Marshak, et al., 1987). Subject answers are then compared to the actual situations that existed at each time interval to determine the subject's overall awareness of the situation. SAGAT has been shown to have face validity, empirical validity, and predictive validity. However, this technique normally measures more then spatial awareness, and some critics believe that this technique does not even directly measure SA but rather what subjects can recall, a criticism that befalls search/replace measures as well (AIAA/ANSI, 1993). Another SA technique is the Situation Awareness Rating Technique (SART) (AIAA/ANSI, 1993, Taylor & Selcon, 1990). SART treats SA as a complex construct and uses several (3 or 10) separate measurement dimensions to get a complete picture of it. Therefore, it is not optimized for pure spatial awareness measurements.

Of all the metrics presented in this section, several can be excluded for use in this effort. Due to the egocentric nature of this thesis, exocentric measures (i.e., map drawing) are of less interest. Since the initial virtual world study will consist of only one room, navigation tasks can be eliminated. SAGAT is designed to be a direct measure of SA and as such involves factors besides spatial awareness. Orientation metrics alone do not appear to be a complete measure for this research but can be considered a subset of the search-and-replace tasks. This leaves distance estimation and search/replace metrics as potential measures.