Abstract: A moving target discriminator uses only bearing information obtained from passive observations together with information about the movement of an observation platform to discriminate whether an object is moving. An underlying principle of the moving target discriminator is that the intercepts of successive line-of-sight observations taken from the moving platform will move only if the object is moving. In a specific embodiment, three line-of-sight observations are made, and an intercept is computed for two different pairs of observations. If the intercepts coincide, the cited object is classified as stationary otherwise, it is classified as moving. Measurement statistics are used to compensate the computed intercepts for navigational and observation errors.