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7 Geographic Orientation For a tank crew, developing an accurate mental model of the environ- ment in which the battle is likely to take place is especially important during the critical period prior to the onset of a battle. The performance of this task is mediated by a number of general factors: workload, stress, fatigue, and environmental conditions. This chapter focuses on some of the general factors involved in the development of the team commander's model of the world and how those factors affect his geographic orientation and workload. Although each of the factors mentioned above mediates a tank commander's battlefield success, his ability to maintain geographic orienta- tion (i.e., awareness of one's location in the world) may be the most critical. The successful tank commander needs to know where he is (present posi- tion), where he is going (objective), and the position of both friendly and enemy forces (knowledge of his battle area) at all times, in order to com- plete the mission. Without this knowledge, situational awareness (knowl- edge of the dynamically changing environment) may be lost, and comple- tion of his portion of the battle plan may not be executed successfully. If the firepower of his team is critical to the success of the mission, the battle could be lost. The following pages provide a general review of the theoretical basis of geographic orientation. Then, drawing the close analogy between naviga- tion in tanks and in helicopters, we describe the specific navigational tasks confronted by operators of these two vehicles. The chapter concludes by placing these tasks in the context of the phases of workload transition. Although geographic orientation is critical for the tank crew, it is equally 171
72 WORKLOAD TRANSITION important for at least one other transition team, the helicopter, whether an emergency medical services craft suddenly called for a rescue mission, or a combat vehicle called into battle. Even in systems in which the world of concern is small, such as the nuclear power plant, geographic or spatial orientation will become critical if the operator must diagnose the location and topology of a fault within the complex interconnections of the system. WHAT IS GEOGRAPHIC ORIENTATION? Geographic orientation is not a term defined by Webster. But, using Webster's definition for geography and orientation, it may be approached as the sum of two terms: (1) geography: the features, especially the surface features of a region, area or place and (2) orientation: position with relation to the point of the compass; familiarization with, or adaptation to, a situa- tion or environment; specifically in psychology, interpretation of the envi- ronment as to time, space, objects, and persons. Deaver (1949) defines orientation as encompassing two psychological senses: awareness of one's spatial and temporal position within an environmentally defined frame of reference, with respect to mental rotation. Thus, we can define geographic orientation as: (1) awareness of one's relationship to physical features (especially the surface features) of a re- gion, (2) one's awareness of relative location within that region (e.g., the center or the edge), and (3) one's temporal awareness of when one should arrive at locations within that region. For tank commanders or helicopter crews, geographic orientation refers to their knowledge of the environment through which they are moving and to the relationship between where they are, where they should be, and where they are going. Since the visual scene is continuously changing, geographic orientation is a dynamic process. It requires navigators to focus their visual attention on the immediate environment, to maintain directional control and to avoid obstacles, while simultaneously relating information in the visual scene (a forward view) to remembered landmarks or those depicted on hand- held or electronic maps (a downward view). Correlating the outside visual scene with maps that depict the same area is cognitively demanding and requires mental rotation and resealing at least. The difficulty of this task is further increased when objects that are visible in the forward field of view do not appear on the map, objects are represented by labels or symbols rather than pictures, and significant landmarks are obscured by other terrain features, reduced visibility, or both. How do operators attain and maintain geographic orientation during operations? Before we can understand this process, we should examine some of the general factors involved. The following sections will review:
GEOGRAPHIC ORIENTATION 173 (1) The issue of constraints on spatial awareness: What physical fea- tures permit and constrain people's orientation in the world around them? (2) Spatial frames of reference: How do people represent or understand their position in the world? (3) How do factors such as confirmation bias (e.g., expectancies) and object comparison processes (i.e., comparing map objects or symbols with viewed objects) affect orientation? (4) Language: How do people communicate relative positions (i.e., use verbal information to aid in self-orientation and that of others)? (5) Timing: How do people remain aware of where they should be while on the move? REAL-WORLD CONSTRAINTS ON SPATIAL AWARENESS The world around us provides a basic structure within which our orien- tation is defined. It determines both how position and movement can be defined and measured and how we can come to know our position (i.e., how we can achieve orientation). According to Shepard (1984), the most perva- sive and enduring constraints in the world in which we have evolved are likely to have become internalized in the nervous system As a conse- quence, such internal constraints may be both so abstract, and so much a part of ourselves, that we are ordinarily unaware of them. The following may be considered the fundamental constraints on our experience of geo . . . grap tic orientation. Space is three-dimensional and locally Euclidean. Rigid motion of an object can be defined by six degrees of freedom: three are translational and three are rotational. The earth's gravitational field determines a locally unique upright that is orthogonal to an approximately flat surface. When, as observers, we are constrained to this surface, we possess: (1) a unique top (the head) and bottom (the feet) defined by our standing orientation, (2) a unique front and back defined by the direction we are looking and our direction of travel, and (3) a basic laterality that defines our right and left sides (Shepard? 1984) but is less salient than the vertical and fore-aft di- mensions. There are more subtle constraints that may be internalized as well. For example, on a flat horizontal surface, a person may move in any direction defined with respect to the north-south, east-west frame of reference. North- south and east-west are not abstract concepts, since they may be internal- ized with respect to consistent phenomena in the world (e.g., the sun rises in the east and sets in the west; and when one faces east, north is always on the left, and south on the right). This frame of reference may be contrasted to the earth's magnetic field, a natural phenomenon that is not directly visible but that provides a cue to direction when depicted by a compass.
74 WORKLOAD TRANSITION Frames of Reference Frames of reference are the basic spatial cognitive models by which we define where we and others are in the world. As such, frames of reference are obviously critical elements in any account of human navigation. Three different frames of reference have been proposed as crucial to successful geographic orientation and locomotion. The first, one's egocentric or ego frame, is defined with respect to an observer's body (e.g., above/below, front/back, and left/right). The second, a container, world, or environmental frame, defines loca- tion with respect to physical or imaginary world lines or surfaces. The most familiar container frame, altitude, is defined by the physical dimension of feet above sea level (up/down) and the more imaginary latitude (north/ south) and longitude lines (east/west) is defined by degrees, minutes, and seconds. Other container frames can be defined with respect to more con- crete boundaries, such as tree lines or rivers. The most important feature of container systems is that their utility diminishes as the observer gets farther and farther away from the relevant lines or features. Thus, earth latitude/ longitude coordinates would provide a very poor reference system for locat- ing features on the surface of Mars, and position relative to streets in New York yields poor localization for places in Trenton. The third type of reference frame is an object-centered frame, in which locations and directions are defined relative to fixed landmarks (e.g., mountaintop, valley, outlook tower). In some ways it shares properties with both the container and the ego frames. It can be defined with respect to axes run- ning parallel to the top/bottom, front/back, leftiright, or sides of some ob- ject. Thus, it is very similar to the container frame in that it has important world lines or surfaces. However, it is similar to the ego frame as well, inasmuch as the concept of left/right is involved. Although all three frames and their associated dimensions can be of critical importance for an individual, their perceptual availability differs greatly. For example, the gravitationally defined up/down dimension is accessible in all three frames by vestibular and visual cues (e.g., objects typically have perceptually distinct tops and bottoms). However, vestibular cues are subject to the effects of motion. The front/back direction is also generally quite salient. Even though front/back is not as invariant a dimen- sion as gravity, it is useful. FrontAback is available in the egocentric frame (e.g., what can and can not be immediately seen or approached by natural locomotion) and given in the object-centered frames (e.g., the distinct front and back of those objects). The limitation to the usefulness of this dimen- sion is that, in the egocentric frame, front/back changes with the orientation of the observer relative to an object while, in the object-centered frame, it depends on the presence of a natural front and back to the object.
GEOGRAPHIC ORIENTATION 175 Rather than being an unwanted complication, the presence of more than one reference frame may be a prerequisite for navigation. The key to navigational awareness is a comparison and verification process: Am I (ego frame) where I should be (world frame)? When these two representations map onto each other, geographic orientation is maintained; visible objects correspond to those that are expected to be in a particular location in the world. When they do not, disorientation will result, which is a potentially disastrous condition during any combat mission. For example, Wickens (1989a, 1989b), in his discussion of the multidi- mensionality of navigational performance, suggested that spatial awareness (one category of navigation performance) is based on the congruence be- tween the ego and world frames of reference. The navigator attempts to maintain congruence between his position and orientation in a world frame specified by a physical or cognitive map (see Tolman, 1948, for a discus- sion of cognitive maps) and what he can see in his ego frame (e.g., his forward field of view). The cognitive representation, which is normally derived from earlier map study and verbal reports, may be stored as a spatial representation (cognitive map) or as a route list (a serial list of verbal descriptors, such as "follow the right fork of the river for three miles then turn Weston. The congruence model states that two views, or frames, are congruent if two pairs of points can be brought into a one-to-one rela- tionship (see Maxwell, 1975, for the mathematical formalization of the con- gruence concept). In the present case, this means that a person is oriented if he can match two points visible in the scene with two points on a physical or cognitive map. Although both frames of reference are compared to maintain spatial orientation, they tend to serve rather different functions. For example, we use the world frame to convey compass heading and cardinal directions (north, east, south, and west), while we use the ego frame to convey relative bearing (right, left, front, and back) and clock direction (e.g., aircraft at a 2:00 bearing) when verbally communicating. Similarly, in the control of locomotion we tend to use the ego frame to characterize the more dynamic, "inner-loop" variables related to vehicle control (pitch, roll, and yaw) and obstacle avoidance; we use the world frame to characterize the control of more slowly changing "outer-loop" variables (position relative to large- scale terrain features). Reference Frame Comparisons Shepard and Hurwitz (1984), in a study of mental rotation during route following, found that reaction time increased significantly as the route that was followed departed from an up/down map direction. They suggested that a compensatory mental rotation of the egocentric frame of reference .
176 WORKLOAD TRANSITION was performed in order to judge the direction of turns as the route deviated to the left or right. Two forms of spatial rotation are required for navigation: (1) Physi- cally rotating a map, or its mental representation, so as to keep the depicted or imagined direction of travel always pointing directly away from the map reader; a track-up orientation. This horizontal rotation may be accomplished by physically rotating a paper map to a track-up orientation or by mentally rotating a map that was stored in a north-up orientation. (2) Mentally rotating a two-dimensional plan view of the environment that is perpendicu- lar to the line of sight to yield an imagined perspective view. This forward mental rotation is used to compare a mental image with the perspective forward field of view. Evidence for the reality of these mental rotations can also be found in studies by Aretz (1988~; Cooper and Shepard (19731; Shepard and Metzler (1971~; Eley (1988~; Evans and Pesdick (1980~; Harwood (19891; Hintzman et al. (1981~; Levine (1982~; Shepard and Hurwitz (1984~; and Sholl (1987~. Each type of rotation requires time, and the processes seems to be additive. These studies have shown that the time needed to visually compare two stimuli increases linearly with the angular misalignment between their ori- entations. Aretz (1991) found that the time required to mentally rotate a map to bring it into alignment with the external scene increased from 3.7 to 4.2 seconds as the difference in orientation increased from 0 to 180 degrees in a helicopter flight simulation. If one considers this rotation effect in terms of a static environment, the milliseconds required to perform this task seem insignificant. However, when considered in the context of a real-world dynamic navigational task, where object and scene recognition is a continuous process, the magnitude of this time-consuming process becomes evident and the greater time de- mands are also more likely to cause errors. Biases in Geographic Memory A mentally generated scene used for comparison with a forward field of view may be stored in memory. Typically, it is derived from map study prior to the start of a mission. However, it has been found that figures (such as symbols or icons on a map), especially those with odd shapes, are difficult to orient in mental space. Therefore, heuristics (rules of thumb) may be adopted to facilitate the coding and retrieval of the spatial orienta- tion and location of these figures. Principles of perceptual organization suggest that people use two such heuristics, rotation and alignment, and that both lead to subtle, but important, biases. When it is difficult to remember the exact positions or rotations of
GEOGRAPHIC ORIENTATION 177 figures, either or both of these principles of perceptual organization (i.e., rotation and alignment) may be invoked for anchoring figures in frames or shapes in space. When the rotation heuristic is applied, the natural axes of a figure and the axes of its frame of reference converge. When the align- ment heuristic is applied, two or more nearby figures group together. As a consequence of invoking the rotation heuristic, people tend to remember figures as being more rotated in memory such that their primary axes are oriented so as to be similar to the principle axes of the reference frame (Braine, 1978~. Since vertical and horizontal are natural axes for describing both figure and frame in sensation, perception, and language, these are the most likely candidates for rotation (Rock, 1974~. Thus, invok- ing the rotation heuristic will generally result in figures being remembered as being more vertical or more horizontal than they actually were. Alignment is related to the phenomenon of perceptual grouping. As a consequence of invoking the alignment heuristic, people tend to remember figures that gravitate toward a simpler structural grouping than they actu- ally possessed. When this heuristic is invoked, arrays of figures are remem- bered as being more orderly or aligned than they were. What is remem- bered, then, is a compromise between the actual stimulus pattern and a more regular, easily remembered pattern (Gogel, 1978~. These heuristics may be invoked during the formation or encoding of representations of the visual world, during the storage of these representa- tions, as well as in the later use of these representations. They are approxi- mation techniques that facilitate memory, but at the expense of distortions of locations and orientations. The heuristics may also allow inferences when information is incomplete; for instance, when comparisons are made across regions that have not been stored together. In these cases, best guesses must be made about relative orientation or alignments of stored representations. For example, Tversky (1981) found that these biases af- fected performance in map reproduction, recall, and recognition memory and that they were adopted in storage, when spatial positions were difficult to encode, as well as in inferences to fill in gaps of knowledge. Tversky presented evidence for systematic distortions in memory for real-world maps, artificial maps, local environments, and visual forms. For all of these di- verse stimuli, the distortions have the same characteristics reflecting align- ment and grouping heuristics. For example, the position of stars is remem- bered by aligning them with one another to form meaningful structures (i.e., constellations). The alignment and rotation heuristics have been demonstrated in the way people remember familiar, naturally occurring stimuli, as well as for new information acquired from artificial stimuli (Palmer, 1980~. They have been demonstrated for information acquired from artificial navigation (e.g.,
178 WORKLOAD TRANSITION path following in a laboratory study) of environments, information acquired from maps for visual forms, as well as geographic entities (Stevens and Coupe, 1978~. Particularly important for navigation is the finding that spatially ex- tended stimuli (e.g., highways and mountains) induce their own axes in the normal course of perception (Braine, 1978; Howard and Templeton, 1966; Rock, 1974~. These coordinate axes, which can serve as an induced con- tainer frame, may interact with object-centered reference frames. This causes the container axes and the object axes to appear, or be imagined, to be in greater alignment than they actually are. For example, during a recent field study, emergency medical services (EMS) helicopter pilots were asked to draw maps of their service areas. Their maps depicted highways that gener- ally parallel northwest to southeast mountain ranges as straight lines (Battiste et al., 1989~. The east and west ranges of hills in the San Francisco Bay area serve as a container for this area, thus spatially extended stimuli (high- ways, powerlines, etc.) are remembered as being more aligned with these hills, than they actually are. But this does not affect their ability to perform required piloting tasks. Hierarchical anchoring is another important heuristic that people use to help them remember geographic information. For example, Stevens and Coupe (1978) presented evidence that people remember the position of large geographic units, such as states, remember which cities belong to which states, and then use the location of the state to remember the locations of the cities. However, systematic distortions may result from using this strat- egy. For example, subjects report that Reno is farther east than San Diego. However, comparing these two cities on a map, one can easily determine that Reno is the more westerly city. ~^ his occurs because the state of Nevada is thought to be east of California. Since Reno is a city in Nevada, it is thought to be east of any city in California. Thus, this heuristic makes it difficult to directly compare locations nested within different higher-order units. While Tversky (1981) presented evidence for systematic distortions in remembered location and orientation, other researchers have demonstrated systematic distortions of distance relations among elements. Thus, two points are judged to be closer when they are within the same object or contour (container frames) than when they are in different objects or con- tours (container frames) (Coren and Girgus, 1980~. For example, a distance within a large city would be judged closer than an equal distance between two cities. Reference points also affect distance judgments. Distances between objects and a point of reference that is near are overestimated, while dis- tances between objects and a point of reference that is distant are underesti- mated. That is, spatial discrimination is greater when closer to a point of reference.
GEOGRAPHIC ORIENTATION 179 Reference points can also induce asymmetry in distance judgments. Ordinarily, places and landmarks (i.e., important points of reference) are judged to be closer when places are compared with landmarks than when landmarks are compared with places (Sadalla et al., 1980~. That is, when proceeding toward a landmark from a place, the distance would be judged closer than when proceeding from the landmark to a place. Thus, reference points and figural properties also affect how spatial knowledge is organized in memory and yield systematic errors in distance judgments. The problem of remembering spatial locations of figures is similar to the problem of remembering the order of a list of verbal items; for both, structure promotes memory but may induce distortions. Whether or not these biases exert significant influence on the absolute recognition proce- dure employed in a navigational task is unclear. For example, would a tank commander or a locomotive conductor become confused if the viewed cur- vature of a mountain is greater than the simplified (i.e., straightened) men- tal representation of the mountain? Another potential distortion is related to the way people forget particu- lar image features that might be used for object comparisons. An assump- tion made by some researchers in this area, which is supported by pilot interviews, is that during map study, people imagine a three-dimensional representation of a feature depicted on two-dimensional maps. These three- dimensional images are later remembered for comparison with their view of the "outside" scene (Eley, 1988~. Do people, during map study, imagine three-dimensional forms for comparison with their forward field of view? Do they forget these distinctive shapes when comparing their mental repre- sentation to the actual figure? How well is seasonally variable ground or vegetation texture imagined when studying a map, and how much of this detail is remembered? Biederman's (1987) work on the basic components of object recogni- tion may provide a useful framework for understanding landmark memory and forgetting. Also relevant here is the fact that memory of object shapes tends to be biased toward the symmetrical representation, as mentioned earlier. Language As studies in the field of linguistics (Fillmore, 1968) and psycholinguistics (Clark, 1973) make clear, the fundamental spatial facts of the world are reflected not only in our perceptual and cognitive structures, but also in the way we talk about the world. For example, there is considerable evidence suggesting that the primacy of the up/down dimension affects not only how we see and think about the world, but also the very words we use to talk about the world.
180 WORKLOAD TRANSITION With regard to language, children learn and successfully use terms per- taining to up, down, front, and back long before they master terms pertain- ing to left and right or to north, east, south, and west. Also, the terms up and down are universally used to refer to any directions in the horizontal plane (e.g., he traveled up North, they went down South, "he walked up to the front of the room," "they walked down the street together". Clark (1973) also noted the significance of referring to the direction of the reference object as up (e.g., they climbed up to the top), suggesting that things above the ground plane are snore accessible than things that are below. Therefore, the upward direction seems to cognitively dominate the downward direction. As global navigation grew in importance and with the invention of the magnetic compass, the unique poles of the earth became more appropriate, accessible, and invariant reference points. And since most of the global navigators and map makers came from the northern hemisphere, the asso- ciation between spatial proximity and the absence of linguistic markings would favor the north pole as the reference point for up. These reasons can somewhat explain why the direction of north has come to mean up in navi- gation and communication among navigators, and also why north is conven- tionally oriented at the top of maps. In a simple universe, with only one natural frame of reference (egocen- tric frame), one might not have a need to imagine rotations in space. How- ever, our daily world, and the world of pilots and tank crews, coordinating with each other and with fixed bases on the ground, are greatly complicated by the fact that people who must coordinate their activities may occupy many different ego frames of reference over time (as a result of locomotion) and space (there may be more than one moving observer). Thus, as two vehicles move independently about a common terrain, the relations between the principal directions of each frame constantly change. Although the upward vertical direction remains aligned across all of these frames (ego- centric, object, and container), what was on the "right" may move to the "left" (if the viewer moves) or what is on the right for one observer may be on the left for another because it is perceived from a different vantage point. Mental rotations of perceived and expected scenes or placing our- selves in the perspective of another may facilitate anticipation, planning, and communication in such a world. Timing While orientation in space is an important issue addressed by the con- cept of frame of reference, the equally important issue of orientation in time is not. Many aspects of the tank commander's duties involve timing: arriv- ing at initial battle position on schedule, crossing way points on time, and
GEOGRAPHIC ORIENTATION 181 coordinating arrival times with other teams. It is the tank commander's responsibility to monitor the passage of time during maneuvers. Although most commanders wear watches, continuous monitoring is not possible be- cause other tasks require their attention. Thus, temporal orientation in- volves more than whether or not the tank commander has a watch. How do people maintain temporal orientation? Gibson (1968) argues that there is no such thing as the perception of time, but only the perception of events and surfaces. Events, in particular locomotion, do not occur in space but in the medium of an environment that is rigid and permanent. Gibson argues that abstract space is a "ghost" of the surface world, and that time is a ghost of the events of the world. Following his logic, it is not difficult to understand that humans are not very astute time estimators. However, humans are very good at perceiving events. Pilots, during low- level flight, know when to start looking for features in the terrain that they plan to use as orienting landmarks. Typically, when clocks are not used, pilots' estimates of clock time are based on relative distances and speeds of travel. This method of keeping track of time (e.g., tracking physical events) is very different from keeping track of clock time. There is considerable support for Gibson's belief that time is a ghost abstracted from event structure. For example, Hart (1978) obtained evi- dence suggesting that people do not perceive time directly but employ strat- egies for monitoring its passage. She used subjective time estimates as indices of workload and found that commercial airline pilots' abilities to actively keep track of time varied as a function of the demands of other flight-related duties. When pilots were asked to estimate 10-second inter- vals, Hart found that the estimates increased from about 10 seconds with no competing activity to 14 seconds in the presence of a difficult concurrent tracking task. She also found that the variability of their estimates in- creased with higher task demands. Hart asserted that, as task demands increased, there is less attention available for active time estimation. Simi- lar results were obtained during a simulation conducted at Wright Patterson Air Force Base (Gunning, 1978~. During the active mode of time estimation, there are many timekeeping techniques: tapping, counting (both aloud or silently), using remembered events, counting heartbeats, etc. These methods are used to fix an individual's attention on the passage of time and makes the process more concrete. However, these externalized methods are easily disrupted by more compel- ling activities and are impractical in an operational situation. In response to the problem of estimating time under very high levels of workload, Hart suggested that people seem to switch from an active produc- tion mode to a "retrospective mode" of time estimation. With retrospective estimation, people use the number of events that occur during an interval as a measure of the amount of time in that interval. In her study, Hart found
182 WORKLOAD TRANSITION that extreme levels of workload began to yield produced durations that were less than the 10-second interval. This is predicted by her model for high- workload situations in which the number of task events per unit time is high. And she obtained reports consistent with this model during interviews with the pilots; time seemed to pass quickly when they were very busy and slowly when they were not-a feeling we have all experienced. The pilots in Hart's study also were aware that they made consistent errors of estima- tion under conditions of high workload. Hutchins (1983), during his cross-cultural studies of the Island Naviga- tors of the South Pacific, found that these navigators also used the passage of events (star points relative to a reference island) to estimate trip duration, time of arrival at way points, and arrival time at the destination island. The results from Hart's laboratory, simulation studies, and Hutchins' field stud- ies would seem to support Gibson's assertion that we do not, or cannot, actively keep track of time directly, but that we track events that provide estimates of time. The implications of the workload-related biases in time estimation for navigation are direct. To the extent that the expectancies for landmarks along a route are based on the passage of time when traveling at a given speed, then time estimation errors can distort the sense of when landmarks may be expected. Depending on how time estimation is dis- torted, landmarks may be expected too early, yielding a premature sense of lostness, or too late, creating the possibility that a landmark would be over- looked if it was passed before it was expected. Mental Models of Navigational Tasks Since there are many ways to solve a complex problem, the solutions most likely to occur to a researcher are those that arise from the traditional assumptions of his or her own culture. Hutchins's (1983) chapter on Micronesian navigation shows how easily such cultural biases can mislead an "unbiased" observer, and how convincing an inaccurate explanation can be to the for- mulator, even in the face of relatively serious anomalies. What we want to do is not model how a scientist conceptualizes a task, but rather how real problem solvers conceptualize the task. In doing this, we need to identify how the task is actually solved and the internal processes that are employed. It is necessary to determine how the problem solver defines the task, the set of operations used to operate on his or her representation of the task, and how these relate to the set of operations required in the world. Then we may ask the question: How could one operate on that representation to produce the decisions required to accomplish the task? For example, the Island navigators in Hutchins' chapter use a mental image of a reference island moving along a defined track (defined by a mental star map) to determine their exact location along a route between two islands.
GEOGRAPHIC ORIENTaTION 183 The task of terrain navigation as performed by helicopter pilots (during low-level and nap-of-the-the-earth, NOE, flight) and tank commanders more closely approximates that of the Polynesian navigator, the Eskimo, and the Touareg nomads, than that of a typical ship or aircraft navigator. The helicopter pilot and tank commander, like the Micronesian navigators, must determine and update their position in the world by discriminating, inter- preting, and organizing subtle terrain distinctions in an environment that appears to be uniform. Wickens (1989a, 1989b) proposed a model of navigation to explain the way cognitive models are developed and used for navigation by helicopter pilots in NOE or contour flight conditions. lIe reported that there is little information in the form of a well-developed model that directly pertains to the task of navigation when surrounded by terrain. Hence, the model he proposed consists of components derived from research in the area of visual perception and spatial cognition, coupled with information gained by con- sultation with operational pilots. The components of the model are presented in Figure 7.1, which pro- vides an integrated framework for the information that preceded this section and can be used to integrate the tank commander's task for the consider- ation of workload transition. Through the use of this model, which seems to capture both the dynamics and the components of the navigational task, experiments can be designed to address the fundamental characteristics of the navigational task. In such a model, a key component is the need for the navigator to compare the perceptual view of the world, which is ego-referenced and shown in the lower right of the figure, with more abstract goals and expec- tations of where one should be. The latter are often expressed in a world frame of reference (e.g., "I should be heading northwest"~. The mental transformations necessary to compare the two representations (e.g., "Am I where I should be?") are shown at the bottom. These may take time and mental effort and be subject to error. Furthermore, the navigation process may depend on long-term memory and geography, whose distortions were discussed above, as well as working memory, whose demands impose a major source of workload. GEOGRAPHIC ORIENTATION: TANKS AND HELICOPTERS Since little research exists on tank navigation, this review borrows heavily from research experience in rotorcraft operation, a system that is in many respects analogous to the tank. An indepth analysis of navigational seg- ments of different types of vehicles (i.e., automobiles, fixed- and rotary- wing aircraft, and tanks) reveals that the navigational demands of the tank and the helicopter have far more in common with each other than with their
184 Attention Long-Term ~En , Memory ~' Working Memory , ~, Planning & ' Map ~' Anticipation ' Representation ~l ~ ~ ~ , ~, ~ ED = RxT , , ~, , ~ / ~ _ 'a Biases & ~' Landmark / 2 ~ i, ~ Rep resee tat i o no ~,/ , Human Operator Em, (1 ) (2) (3) Horizontal Forward Image Rotation Rotation Comparison Image ~ Triangulation Generation * Alignment ~ Obyect Comparison FIGURE 7.1 The Wickens Model of Navigation. WORKLOAD TRANSITION Environmental Inputs - Map - Flow Field - F FoV* - Verbal Inputs Forward field of view corresponding ground and airborne counterparts (automobiles and fixed- wing aircraft, respectively). For example, both fixed-wing pilots and auto- mobile drivers typically follow paths with tight lateral constraints high- ways and roads for the automobile driver and airways or preselected courses for the fixed-wing pilot. The automobile driver and fixed-wing aircraft pilot can usually follow their selected route with little regard for surround- ing terrain features, in marked contrast to the tank driver and rotorcraft pilot (during low-level flight), who must use surrounding terrain features to iden- tify the route to be followed. Hence, we now consider the common features of the navigational problems presented by these two systems. Tank crews and the pilots of military or civilian helicopters flying at
GEOGRAPHIC ORIENTATION 185 very low altitudes are faced with a challenging situation. They operate so close to the ground that local terrain features may obscure their view of significant landmarks, thus reducing their visual range and making it diffi- cult to relate local terrain features in a more global context. Often, tanks and helicopters move freely through terrain, without an explicit, visible or electronic, route to follow. While there are many degrees of freedom in this environment (tank and helicopter crews are not limited to roads or elec- tronic routes as are automobiles and fixed-wing aircraft flying typical cross- country routes), it is more difficult to maintain the desired course, and natural and artificial obstacles pose a very real threat. In this environment, helicopter and tank crews must correlate cues viewed in the external scene with information on paper maps to maintain geographic orientation, avoid obstacles, and maintain their course. Instruments that provide pilots with information about speed and altitude are relatively inaccurate at low alti- tudes and slow speeds, and electronic aids are intermittent at best, because they require line-of-site with the source to work properly. There are no instruments in tanks to aid in geographic orientation. Before a mission, helicopter and tank crews study maps of the environ- ment in which they will operate to select a route that offers the most direct path to their destination (given terrain contours, obstacles, etc.), distinctive visual cues (to aid in geographic orientation), and cover (if there is an enemy threat). They select specific features that they will use during the mission to verify their location and identify choice points (e.g., intersec- tions of rivers, hilltops, clearings, groves of trees). They might identify linear features that can provide a visible "route" to follow (e.g., ridge lines, river valleys). However, military crews generally do not select constructed structures for reference (things change) and avoid following roads (the en- emy threat is greater there). Tank and helicopter crews incorporate the available information into a cognitive model or mental map of the environment through which they will travel. The mental representation might be spatial a mental image of the map (a plan view) or a series of perspective mental images of how signifi- cant features in the environment are likely to look when viewed from the cockpit of a helicopter or turret of a tank (a forward view). Alternatively, they may store this information as a route list a series of verbal commands (e.g., "travel down the valley for two miles then bear right") or descriptions (e.g., "follow the creek that runs beside the cliff") that are remembered and executed during the mission. During a mission, helicopter or tank crews view features in the external scene and compare them to a paper map or their mental images. They must mentally transform the stylized images on two-dimensional maps into men- tal images, which represent a perspective view of the object, which is ro- tated into alignment with the forward field of view, for comparison with the
86 WORKLOAD TRANSITION external scene. If they continue to see expected features on time and in the correct order, they know where they are; visible terrain features correspond with their expectations and they can correlate their position with a location on the map. When they pass a distinctive feature (e.g., a water tank de- picted on their map) or an intersection of linear features (e.g., two ridge lines intersecting), then they know precisely where they are. However, if a single landmark is symmetrical, they may know generally where they are (e.g., approximately two miles from a water tower), but not their precise position (e.g., approximately two miles west of the water tower) or their direction of travel. In this case, they may look for a second reference point, check the compass, look at the sun, or infer direction from previous cues. When using a ridge line that extends for some distance as a geographic reference, a crew knows only that they are traveling in the correct direction, but not their precise location. Depending on the familiarity of the terrain, the availability of distinc- tive features, and the quality of premission planning, maintaining a route may be relatively easy or very difficult. For example, when a crew must rely on subtle variations in terrain to judge location, it may be extremely difficult to relate the visible features in the forward scene to contour lines on the map. This task is particularly difficult if surface contours are masked by vegetation. Furthermore, the appearance of terrain and vegetation varies seasonally and from one region to another, requiring adaptation and infer- ence. There may be considerable ambiguity about whether a particular feature is, in fact, the one a crew expects to see or the specific feature depicted on the map. As the time between landmarks increases, uncertainty about current position may increase if additional cues are not available for the crew to verify that they are, in fact, where they think they are. At some point, the crew will begin to look for the next expected landmark. If it does not appear by the expected time, the crew may begin to consider the possibility that they are lost. If a feature that is similar to their expectations appears, the crew may identify it as the expected feature. If it is not, it may take some time before they accept the growing evidence that they are not where they are supposed to be. At this point, the crew must take action to reestab- lish their position. A helicopter pilot might gain altitude or a tank com- mander drive to the top of a hill to find a distinctive landmark. If this is not possible, the crew may carefully survey the surrounding terrain and try to find a pattern of features on their map that corresponds to what they see. However, it is much more difficult to find a pattern somewhere on a map that corresponds to the forward scene than to verify that a visible feature is where it is supposed to be relative to the vehicle. Alternatively, they may try to retrace their path until they find a familiar landmark. However, the mental preparation performed before the mission will be of little help here,
GEOGRAPHIC ORIENTATION 187 as terrain features and relationships will not correspond in the expected sequence. Thus, maintaining geographic orientation requires helicopter and tank crews to continuously correlate the visual scene with the map. To do this, they must accurately estimate their speed and distance traveled. Estimates of when to begin looking for a landmark, when a choice point has been missed, or what features should be visible at any point in time are based on subjective estimates of the distance traveled and time elapsed since the last known location. When operating at night, tank and helicopter crews rely on night vision devices (that intensify light or display infrared imagery) to provide them with information about the external scene. Although they could not perform required missions as well without these devices, their use imposes consider- able additional load on the pilots: field of view is limited, acuity is re- duced, depth cues are distorted, subtle textures necessary to identify a par- ticular feature may be missing, and objects or terrain features may look very different than expected. Furthermore, greater navigational precision is required at night; obstacles that can be seen and avoided during the day may be invisible at night. Thus, pilots rely on maps to spot potential obstacles. However, this information is useful only if they know exactly where they are. For these reasons, maintaining geographic orientation becomes signifi- cantly more difficult, and overall performance capabilities may be reduced. For example, pilots are more likely to fly slower and higher at night, and over sand, where texture supporting accurate distance estimation is absent. In tanks and helicopters, crew members communicate with each other through an intercom system (high ambient noise levels and physical barri- ers, in some cases, preclude direct conversations) and with other helicop- ters, ground personnel, etc., through radios. Navigational and geographic orientation information is usually conveyed verbally, although crew mem- bers may use gestures as well (e.g., point to features in the environment or on a map). In helicopter nap-of-the-earth flight, navigation may take as much as 90 percent of the navigator's time, and communications between the pilot and navigator about navigation, 25 percent of both pilots' time. Army aviators use 1:50,000 scale maps that depict terrain contours (e.g., hills and valleys), vegetation (e.g., fields and groves of trees), bodies of water (e.g., rivers, streams, and ponds), and some cultural features (e.g., roads, buildings, bridges, water tanks, and towers). During premission planning, helicopter or tank crews plot their route on the map, identify critical choice points, and select additional features that they will use to verify their posi- tion. In flight, the navigator follows the route of flight on the map, giving the pilot verbal cues about what he should see, when he should begin or end a turn, and potential obstacles. In addition, the navigator scans cockpit instruments, verbalizing relevant information to the pilot. The pilot gener
88 WORKLOAD TRANSITION ally keeps his eyes focused outside the cockpit, telling the navigator what he sees in the external scene and verifying that he does (or does not) see specific landmarks described by the navigator. In a tank, the commander is responsible for navigation, passing verbal steering commands to the driver; particularly when the tank is buttoned up because the driver's field of view is too restricted to maintain geographic orientation. Helicopter or tank crews use or mix a number of different frames of reference when exchanging information among themselves or transmitting to another vehicle: (1) ego-reference/spatial (e.g., a landmark is in front, to the right, or to the left of the pilot; the driver should turn right or left); (2) ego-reference/clock position (e.g., a feature is at the observer's or recipient's 2 o'clock position); or (3) world-reference/compass heading (e.g., the pilot should look for a stream running north-south; an enemy tank is located 5 miles northwest of a friendly tank; another vehicle should turn 20 degrees to maintain a new heading of 280 degrees). Ego-referenced directions are the easiest to process (Aretz, 19901; they require minimal mental transformation or interpretation. Clock positions are less intuitively obvious than right/left directions, although they provide more precise information. However, clock position may be ambiguous if the sender's and receiver's points of reference (i.e., head position) are sig- nificantly different. Furthermore, extracting spatial information given in a verbal form may require additional mental transformations. When giving ego-referenced directions, the originator of the message must mentally project himself into the point of view of the intended recipient, an activity that imposes additional cognitive demands and is subject to error. In both the tank and helicopter environment, the reference frame problem is compounded because the direction of travel of the vehicle may not correspond to the direction the operator is facing. Spatial information that is world-referenced (i.e., to a numeric or verbal compass position) is more precise than other forms and does not require that the sender or recipient project themselves into another's ego-reference. However, steering commands referenced to compass position presuppose that the recipient knows the current heading. In helicopters, the pilot re- sponsible for flying may have no idea what his current heading is because he is focusing on the external scene, rather than on the instruments. Thus, a flight navigator might couple an ego-referenced command (e.g., turn right) that requires minimal mental transformation with a world-referenced modi- fier (e.g., turn right; now you're heading due west) to improve the pilot's orientation. In tanks, there is no compass on the instrument panel, and the metal body of the tank interferes with the accuracy of hand-held compasses. Therefore, compass headings are not used for steering commands in tanks. In addition to the problems associated with the use of different refer- ence systems, tank and helicopter crews often operate in unfamiliar envi
GEOGRAPHIC ORIENTATION 189 ronments in which crew members do not share a common knowledge base about the names and appearance of significant landmarks. Thus, informa- tion about these landmarks must be transferred on the basis of their physical appearance (e.g., a small round pond, a dry river bed, a saddle-back hill), rather than by unambiguous names (e.g., Jones' farm, White Mountain, Route 50~. Given the potential differences in personal experience, descrip- tive terms may have very different meanings for different crew members. For example, what looks like a pond to one may look like a lake to another. A 500-foot hill may look like a mountain to a Midwesterner, but a person from Colorado would describe it as a small hill, and so on. Furthermore, lack of familiarity with local vegetation may make the description process particularly difficult; it is easier to identify a grove of trees by name than by physical appearance. The preceding description of navigational demands of tanks and heli- copters can also be interpreted within the more theoretical framework of research on geographic orientation. In the following section we employ this framework to introduce laboratory research results that have implications for navigational performance in armored vehicles. NAVIGATION AND WORKLOAD TRANSITION When people travel long distances over indistinctive terrain, they often either physically mark the terrain or mentally accentuate whatever distinc- tive features they can find in the environment (Lynch, 1960~. Helicopter pilots and tank commanders during premission planning use both object and container reference systems. On a map, which is usually oriented north-up, distinctive objects (terrain features) are selected to delineate a planned route to the destination and to identify features or objects that will serve as ori- enting stimuli for different route segments. Additional large-scale features, usually linear (e.g., a mountain, valley, or tree line) are selected to contain the mission area. During the mission, the tank commander or helicopter pilot will use all three frames of reference-ego, object, and container. The ego reference system, the most proximal, is used for local course guidance (e.g., keeping the vehicle moving toward the goal) and obstacle avoidance; hence, it is particularly relevant for communications with the driver. The object reference system, a less proximal system, is used to identify current location and general course guidance (direction of travel) to the next object or waypoint. Finally, the container, a more distal reference system, is used to determine the degree of lostness (e.g., when the container boundary is reached prior to a planned location or waypoint, the tank commander is no longer sure of their precise position). Helicopter pilots and tank commanders use both object and container reference systems during the planning and execution of their missions. The
190 WORKLOAD TRANSITION object reference system is used to plot a planned route through an area. The container reference system is used to determine the mission boundaries. During the mission, the object reference system is used to determine exact position to maintain geographic orientation. The container reference system is used to determine the degree of lostness (e.g., whether they have gone past a location that they had planned to use as a waypoint or location fix and are now no longer sure where they are). Multiple reference systems can provide a tank commander with flex- ibility. To the extent that environmental conditions (battlefield conditions) vary, a tank commander must invoke different strategies to accommodate this variability. The Premission Phase During the premission phase, the tank commander is assigned an area of responsibility and battle mission objective. He has to develop a mental model of the area where the battle will be joined. This model includes memorizing the area based on maps (north-up) and verbal reports given by the battalion staff intelligence officer. From these reports, the tank com- mander must develop a plan of attack. This plan consists of a spatial representation of the terrain and the locations of all friendly and known enemy positions. From this spatial representation (usually developed as overlays on a map), the tank commander must select a route to his team's initial battle position and on to the final objective. While selecting the route, waypoints will be selected to break the route into segments. These distinctive features allow the tank crew to periodically update their knowl- edge of where they are (so they will not go too far in the wrong direction), recognize points where course changes will be made, and compare planned versus actual time taken to move between points (to stay on schedule). This plan is developed in conjunction with or communicated to battalion head- quarters and platoon commanders. The workload during this phase of the mission depends on the amount of time available to accomplish these tasks and the quality of information available. The planning phase is informa- tion-intensive. In developing a mental model of the mission area, the tank commander might mentally rotate the north-up map into a track-up perspec- tive to visualize the route and to brief the platoon commanders. In commu- nicating the plan to battalion headquarters, it is likely to be expressed in polar coordinates with reference to a north-up map, so the plan can be correlated with that of other teams. However, in communicating the plan to platoon commanders, the information is likely to be expressed from an ego- centric perspective: first platoon will be on my right, second platoon to my left, etc. During the planning phase of a mission, the tank commander's workload . . ~.. .
GEOGRAPHIC ORIENTaTION 191 is driven primarily by the difficulties of incorporating vast quantities of information, both verbal and spatial, into a spatial (cognitive or paper) map. Aretz (1990), in his study of spatial cognition and navigation, found that map complexity accounted for most (7 percent) of the explained variance in the task. Thus, as map complexity increases, so does processing time and workload. Also, the need to mentally rotate different map frames to com- municate information both up and down the chain of command would affect workload. The Operational Phase During the operational phase, the tank commander must move his forces from their current location to their initial fighting position. He must con- tinually correlate his position in the world (forward field of view) with his map route (world view) to maintain geographic orientation. This is accom- plished by orienting the map to correspond to the direction of movement (track-up) to align the two frames of reference. During this phase, time estimation is very important for determining when objects or features in the terrain, which are used to confirm geographic orientation, should appear. Also, the tank commander must update his estimated time of arrival (ETA) at the initial fighting position based on his estimate of how far he has gone and how long it is likely to take to cover the area remaining. This may be critical, if the initial engagement time must be coordinated with other teams. Transition From Rear Staging Position to Initial Fighting Position The accuracy with which a tank commander must know his team's position during the move to the initial point depends on the proximity of other friendly and enemy positions and the degree to which a precise transi- tion to the initial fighting position is critical to mission success. That is, if the team is trying to stay masked during the transition, then required accu- racy could be very high; if surrounded by enemy forces, maintaining a route designed to maintain cover is critically important. During this phase, com- munications between the tank commander and either platoon or battalion commanders would be very different. For instance, situation reports to battalion headquarters would be given in terms of polar coordinates (world view), while reports from each platoon commander might be given from an ego-centric view (right/left, front/back, or clock positions) of each tank. In the latter case, the tank commander must integrate information from each ego-centered perspective to form a coherent picture of the entire situation into a single frame of reference. The workload during this phase of the mission is likely to be moder- ately high. The tank commander must perform multiple tasks, in parallel
92 WORKLOAD TRANSITION and serially: (1) continuously determine his own position and the relative position of members of his team, other teams, enemy forces, and his objec- tive; (2) estimate and update the time between waypoints and his ETA at the initial fighting position; (3) communicate his own and other positions up the chain of command; and (4) communicate route and mission changes down the chain of command. The difficulty of these activities is deter- mined by the speed at which the situation unfolds, the degree to which it unfolds according to plan, the availability of salient cues to maintain orien- tation, and, most critically, the positional accuracy demanded by mission requirements. The amount of time and effort spent in acquiring geographic knowledge of terrain during the premission phase is also relevant, as this information is unlikely to change during the course of the battle and pro- vides the basic context within which other dynamic events occur. The Preengagement Phase Upon arrival at the initial battle position, particularly if the mission calls for immediate engagement, the degree to which previous phases have been completed successfully (e.g., the planning phase and the transition to the initial position) influences the workload experienced during the battle phase. If the team has successfully completed the previous phases, the battle plan could be implemented without further changes. Thus, workload during this phase would be driven by the accuracy of estimates of enemy strength and the degree to which the tank commander's plan took them into account. If the team arrived late, or at the wrong location, the workload during this phase could be very high. In addition to coordinating his team's actual position with other teams, the tank commander may also have to coordinate with infantry and artillery units (to develop a revised plan). This might require extensive communications using different map frames of ref- erence. Even if the tank commander executed the first part of the plan correctly, he may haste to develop a new battle plan in response to the environment (terrain, time of arrival day or night, enemy activity, etc.) or to a change in the mission. His communications load during the develop- ment of a new plan would be very high: it must be transmitted both up and down the chain of command. During a battle, maintaining geographic orientation is critical to the identification of friendly forces and enemy targets. If artillery or close air support is needed, the tank commander, through his fire support officer, would determine where and how much artillery or close air support is re- quired, in relation to their current position. Again, this requires a transla- tion between a world view (artillery and close air support) and the egocen- tric view (tank commander and fire support officer). Since the commander's tank, and those of his team, are in the battle area, accurate estimates of
GEOGRAPHIC ORIENTATION 193 friendly and enemy positions and accurate communication of those posi . . . . tons are critical to survival. The Post-Mission Phase Whether the battle is won or lost, situation and logistics reports must be compiled. First, the tank commander must assess his team, their position in relation to the battle plan, their losses in equipment and men, etc. The verbal reports from individual tank and platoon commanders must be corre- lated with a map of the area. When receiving reports, the tank commander may orient his map either track-up or north-up. Orienting the map to corre- spond to the frame of reference of each reporter might facilitate interpreting the (ego-centric) communications of team members (e.g., the platoon on the right reports that the enemy forces at their 3 o'clock position have been eliminated, etc.~. A north-up perspective (i.e., the world view) would facili- tate communication up the chain of command, wherein the battalion com- mander must evaluate the report of each team in relation to other teams' successes or failures. The workload during this phase would be influenced by the ease with which a commander could integrate information provided in different frames of reference into a coherent picture of the overall situa- tion. SUMMARY Geographic orientation plays a major role in the success or failure of most tank operations. Platoon and tank commanders must continually up- date their position by comparing different map frames of reference (e.g., their forward view of the world to a paper or remembered map) to deter- mine their position in the world. The level of congruence between different reference frames (and the mental rotation required to bring them into align- ment) will be a factor in determining the time and difficulty of the geo- graphic orientation task, as well as the likelihood of errors. Terrain charac- teristics, required accuracy, familiarity, and planning also affect the level of workload associated with geographic orientation and navigation. To reduce the tank commander's workload, technological innovations such as electronic chart displays (ECD) and premission planners, which can be taken from the mission briefing and downloaded in ECD computers, should be introduced into tanks. (Their utility has been demonstrated in helicopter operations Cote et al., 1985.) Low-cost electronic chart display systems coupled with global positioning satellite (GPS) receivers are being developed to determine and display the exact position of a vehicle superim- posed on a map, a task currently performed by the tank commander using paper maps, at a considerable cost in time and cognitive effort. The cogni
194 WORKLOAD TRANSITION live demands of the geographic orientation/navigation task could be re- duced by the installation of an electronic chart display system that is de- signed to maximize the degree of congruence between the map format, the terrain it depicts, and the tank commander's model of the environment. Different display formats will facilitate the performance of different tasks. The following list of features should allow the system to be both compatible with task requirements and the tank commander's internal model: (1) The system should support both north-up and track-up map formats. The north-up format will facilitate mission planning (multiple missions can be planned and correlated on the same map) and communication between individuals who do not share the same perspective view of the terrain (e.g., headquarters and artillery). Communication between individuals who do not share the same visual perspective must rely on map coordinate data when transferring information. The track-up format will facilitate wayfinding, locating targets, and communication between individuals who share the same perspective view of the terrain (i.e., the tank commander and the driver'. Individuals who have a shared visual perspective can communicate using visual terrain fea- tures correlated with map information to support information transfer. (2) The planned route and the current position of the vehicle should be depicted on the map display. Depicting the planned route and the vehicle's current position on the map eliminates the need to micronavigate between waypoints (thus, the driver's task becomes one of obstacle avoidance and compensatory tracking between waypoints) and facilitates reorientation if the tank becomes lost or makes an unscheduled detour. (3) Map features selected by the tank commander during mission plan- ning to identify route transition points (waypoints) or to aid in maintaining geographic orientation should be depicted on the ECD system. The degree of congruence between the map and the terrain, and also the cognitive compatibility between map depictions and terrain features, may be improved if iconic symbology selected by the tank crew during mission planning is used. (4) Through the use of color and shape coding, contour line information can be accentuated and thus becomes more iconic. (5) Compass information derived from GPS data, scalable range marks, latitude and longitude, bearing to and from selected points on the display, and variable map scales should be available on demand. Also, electronic maps must depict the sort of features tank commanders and helicopter pilots actually use for geographic orientation, represented in a form that is most compatible with the way the feature will appear in the forward scene. By reducing the workload associated with navigation, all of the features should allow the tank commander more resources to deal with
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