Detection

This term refers to the ability of an observer to recognize that something is present within the field of view, even if there is not enough detail to identify specific features of the target. Along with Recognition and Identification, detection is one of the key functions of an imaging system, carrying a unique meaning. These tasks are often described statistically, as they traditionally relate to a human observer’s capability to perform them. The effectiveness of these tasks in a given scenario is measured by the proportion of average observers who are able to accomplish them under the specified conditions. For instance, a “50% Probability of Detection” (sometimes written as P(detect)_50%) means that half of the average group of observers would report being able to detect the presence of something in the image. According to the Johnson Criteria, achieving the 50% detection level typically requires at least 2 pixels on the target.