Detection

This term means that an observer can tell that something is in the field of view, though there is not enough detail to distinguish any features about the target. Along with Recognition and Identification, Detection is one of the primary tasks of an imaging system, and carries a very distinct meaning. Each of these tasks is best described statistically; since these terms historically refer to a human observer’s ability to accomplish the task, how well the tasks can be accomplished in a given situation are described in terms of what fraction of average observers could accomplish it, with the given conditions. For example, “50% Probability of Detection” (sometimes written as P(detect)_50%) means that 50% of an average group of observers would say that they can detect that something is in the image. According to the Johnson Criteria, it takes about 2 pixels on target to achieve the 50% level of detection.