1. An apparatus for predicting a predicted route of a target, comprising: an observing unit for observing the target, having means for determining if the target is observable and means for providing an observed route value of an actual route of said target; terrain information means for providing characteristic parameters of prestored terrain information; and a predicting unit, coupled to receive said observed route value and said characteristic parameters, having means for inferring the predicted route according to a first and a second mode, in which the means for inferring operates according to the first mode, when the means for determining determines that the target is observable, and infers the predicted route on the basis of the observed route value and the characteristic parameters and in which the means for inferring operates according to the second mode, when the means for determining determines that the target is unobservable, and infers the predicted route on the basis of a prior predicted route and the characteristic parameters.