The report consists of notes that have been used in a course on search, detection and localization modeling. Contents: 1) Detection Models and Signal Detection Theory; 2) Decision Criteria; 3) Three Binary Detection Models; 4) General Detection Models; 5) Signal-to-Noise Ratio Detection Models; 6) General Encounter Models; 7) Three Signal Excess Encounter Models; 8) Straight Line Encounters; 9) Two Intermittent Signal Encounter Models; 10) A Random Search Models; 12) A Target State Estimation Procedure; 13) Position Distributions That Change with Motion; 14) Position Distribution That Change with Search; and 15) Search Models and Search Theory. (KR)