1. The process of relating observations or tracks from one set of data to observations or tracks from another set of data, i.e., collecting data from different frames or sensors that presumably relate to the same target. 2. In air defense, the determination that an aircraft appearing on a radarscope, on a plotting board, or visual is the same as that on which information is being received form another source. 3. In intelligence usage, the process which associates and combines data on a single entity or subject from independent observations, in order to improve the reliability or credibility or the information.