Academic journal article Human Factors

Computational Modeling of Foveal Target Detection. (Special Section)

Academic journal article Human Factors

Computational Modeling of Foveal Target Detection. (Special Section)

Article excerpt

INTRODUCTION

Need and Scope

Visual detection by human observers to is considered to be the major operational threat to individual vehicle and unit operation security. The U.S. Army, as well as the NATO countries, have recognized the need for a greater understanding of both the visual signature of their vehicles and the process of detection by human observers using unaided eyes and direct view optics. To this end, the military community implemented initiatives such as the U.S. Army Target Acquisition Model Improvement Program in the early 1 990s and the NATO Research and Technology Organization working group (SCI-12) on camouflage evaluation methods and models. This project was motivated by the need for tools for developmental test and evaluation of military vehicles employing designs and technologies for detection avoidance (i.e., "signature management"). This project was specifically motivated by the need for models of visual detection.

The performance specification for developmental test and evaluation is expressed in terms of detection, given that the observer is looking at, or in the direction of, the vehicle (i.e., foveal target detection). It is not expressed in terms of search time or probability of detection during wide-field-of-view search. Search performance is of interest in operational test and evaluation of large-scale combat, but it is not used in performance requirements for materiel development because search outcome and performance is influenced by many factors over which the materiel designer has no control (e.g., the tactics and operational employment of friendly and threat forces; the large-scale terrain properties). The materiel designer has control over only the vehicle signature and, to some degree, how it interacts with its local surrounding. The performance specifications for signature management are expressed in terms of detection range and probability of detection. In the context of military target acquisition, dete ction means determining that an object is a potential target, specifically a military vehicle. Detection avoidance requirements for ground vehicles invariably address detection avoidance for a stationary vehicle. Moving target detection is considered in combat models but is not currently a major component in developmental test and evaluation.

Objectives

The goal of the project was to develop a robust and accurate analytic model to predict human observer performance in visual vehicle discrimination at the "detection" level for stationary targets, given that the observer was looking at, or in the direction of, the target. The result of this work was a model of target detection called VDM2000.

VDM2000 THEORY

Comparison with Recent Approaches

The visual search paradigm. An extensive body of research in experimental psychology has been developed based on the visual search paradigm. This paradigm, although useful in studies of basic visual attention and perception, does not apply to search for vehicles in natural scenes. The visual search paradigm enables experimental psychologists to control the visual content to which the participants respond and thereby to isolate specific aspects of vision. The visual search paradigm, as described by Wolfe (1998), is characterized by (a) discrete target and distractor figures, (b) a well-defined specific target description, (c) well-defined distractors, (d) well-defined visual attributes with distinctive and discrete values, (e) randomized placement, and (f) a noninterfering and noninformative background.

The standard experimental psychology visual search paradigm eliminates uncertainty on several dimensions important to understanding search in natural scenes. First, there is no uncertainty as to the appearance of the target or the question of what the objects are. Second, this paradigm eliminates the contribution of local and global context in search. These properties make the standard visual search paradigm useful for basic vision and attention research, but they also make it inapplicable to search for vehicles in natural terrain. …

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