Surveillance and Search Theory

Abstract

Surveillance in general involves detection devices, search (allocation-of-effort) procedures, and decisions leading to action of some kind. The purpose of this paper is to indicate briefly the role of search theory within the larger context of surveillance problems. I will discuss elements of surveillance other than search theory: detection and related forms of information gathering; appropriate measures of effectiveness; relevant decisions and their consequences; and most important the sequential nature of continuous evaluation of information. Search problems usually concern an entity that is to be “looked for” and associated action to be taken when it is “found.” The entity is usually a physical object (although it could be nonphysical, such as the value of the maximum of a mathematical function), and the term “target” is natural to use. The person or organization responsible for the looking is called the “decision maker.” The actual expending of effort, with the intent to gain information about the target, is accomplished by the “searcher(s).” By the very nature of search problems, the target’s present status is at any time uncertain, and thus describable only probabilistically. Search theory, in this context, has to do with the allocation of searching effort in such a way as to achieve some stated goal, usually presented in terms of producing an extremal value of some objective function.