Abstract: The methods for determining the probability of detection of a thermally camouflaged target at various ranges by the sensor includes determining an “inherent” temperature difference, ?TRSS, between the target and its immediate surroundings. Once ?TRSS is determined, a scaled N50 cycle criterion, or the number of resolvable cycles needed by the sensor for a fifty percent probability of detection, is determined according to the relationship N50=A/(?TRSS)B+C, where A, B and C are constants that are predetermined according to whether the immediate surroundings are of a woodland or a littoral nature. The scaled N50 cycle criterion is then used in an empirical Target Transfer Probability Function (TTPF) defined by P=(N/N50)E/(1+(N/N50)E), where E=2.7+0.7(N/N50), in order to determine the probability of detection of the thermally camouflaged target.